Java SE 23 & JDK 23

JVMTM Tool Interface

Version 23.0

What is the JVM Tool Interface?

The JVMTM Tool Interface (JVM TI) is a programming interface used by development and monitoring tools. It provides both a way to inspect the state and to control the execution of applications running in the JavaTM virtual machine (VM).
JVM TI is intended to provide a VM interface for the full breadth of tools that need access to VM state, including but not limited to: profiling, debugging, monitoring, thread analysis, and coverage analysis tools.
JVM TI may not be available in all implementations of the JavaTM virtual machine.
JVM TI is a two-way interface. A client of JVM TI, hereafter called an agent, can be notified of interesting occurrences through events. JVM TI can query and control the application through many functions, either in response to events or independent of them.
Agents run in the same process with and communicate directly with the virtual machine executing the application being examined. This communication is through a native interface (JVM TI). The native in-process interface allows maximal control with minimal intrusion on the part of a tool. Typically, agents are relatively compact. They can be controlled by a separate process which implements the bulk of a tool's function without interfering with the target application's normal execution.

Architecture

Tools can be written directly to JVM TI or indirectly through higher level interfaces. The Java Platform Debugger Architecture includes JVM TI, but also contains higher-level, out-of-process debugger interfaces. The higher-level interfaces are more appropriate than JVM TI for many tools. For more information on the Java Platform Debugger Architecture, see the Java Platform Debugger Architecture website.

Writing Agents

Agents can be written in any native language that supports C language calling conventions and C or C++ definitions.
The function, event, data type, and constant definitions needed for using JVM TI are defined in the include file jvmti.h. To use these definitions add the J2SETM include directory to your include path and add 
#include <jvmti.h>
to your source code.

Deploying Agents

An agent is deployed in a platform specific manner but is typically the platform equivalent of a dynamic library. On the WindowsTM operating system, for example, an agent library is a "Dynamic Linked Library" (DLL). On LinuxTM Operating Environment, an agent library is a shared object (.so file).
An agent may be started at VM startup by specifying the agent library name using a command line option. Some implementations may support a mechanism to start agents in the live phase. The details of how this is initiated are implementation specific.

Statically Linked Agents (since version 1.2.3)

A native JVMTI Agent may be statically linked with the VM. The manner in which the library and VM image are combined is implementation-dependent. An agent L whose image has been combined with the VM is defined as statically linked if and only if the agent exports a function called Agent_OnLoad_L.
If a statically linked agent L exports a function called Agent_OnLoad_L and a function called Agent_OnLoad, the Agent_OnLoad function will be ignored. If an agent L is statically linked, an Agent_OnLoad_L function will be invoked with the same arguments and expected return value as specified for the Agent_OnLoad function. An agent L that is statically linked will prohibit an agent of the same name from being loaded dynamically.
The VM will invoke the Agent_OnUnload_L function of the agent, if such a function is exported, at the same point during VM execution as it would have called the dynamic entry point Agent_OnUnLoad. A statically loaded agent cannot be unloaded. The Agent_OnUnload_L function will still be called to do any other agent shutdown related tasks. If a statically linked agent L exports a function called Agent_OnUnLoad_L and a function called Agent_OnUnLoad, the Agent_OnUnLoad function will be ignored.
If an agent L is statically linked, an Agent_OnAttach_L function will be invoked with the same arguments and expected return value as specified for the Agent_OnAttach function. If a statically linked agent L exports a function called Agent_OnAttach_L and a function called Agent_OnAttach, the Agent_OnAttach function will be ignored.

Agent Command Line Options

The term "command-line option" is used below to mean options supplied in the JavaVMInitArgs argument to the JNI_CreateJavaVM function of the JNI Invocation API.
One of the two following command-line options is used on VM startup to properly load and run agents. These arguments identify the library containing the agent as well as an options string to be passed in at startup.
-agentlib:<agent-lib-name>=<options>
The name following -agentlib: is the name of the library to load. Lookup of the library, both its full name and location, proceeds in a platform-specific manner. Typically, the <agent-lib-name> is expanded to an operating system specific file name. The <options> will be passed to the agent on start-up. For example, if the option -agentlib:foo=opt1,opt2 is specified, the VM will attempt to load the shared library foo.dll from the system PATH under WindowsTM or libfoo.so from the LD_LIBRARY_PATH under LinuxTM . If the agent library is statically linked into the executable then no actual loading takes place.
-agentpath:<path-to-agent>=<options>
The path following -agentpath: is the absolute path from which to load the library. No library name expansion will occur. The <options> will be passed to the agent on start-up. For example, if the option -agentpath:c:\myLibs\foo.dll=opt1,opt2 is specified, the VM will attempt to load the shared library c:\myLibs\foo.dll. If the agent library is statically linked into the executable then no actual loading takes place.
For a dynamic shared library agent, the start-up routine Agent_OnLoad in the library will be invoked. If the agent library is statically linked into the executable then the system will attempt to invoke the Agent_OnLoad_<agent-lib-name> entry point where <agent-lib-name> is the basename of the agent. In the above example -agentpath:c:\myLibs\foo.dll=opt1,opt2, the system will attempt to find and call the Agent_OnLoad_foo start-up routine.
Libraries loaded with -agentlib: or -agentpath: will be searched for JNI native method implementations to facilitate the use of Java programming language code in tools, as is needed for bytecode instrumentation.
The agent libraries will be searched after all other libraries have been searched (agents wishing to override or intercept the native method implementations of non-agent methods can use the NativeMethodBind event).
These switches do the above and nothing more - they do not change the state of the VM or JVM TI. No command line options are needed to enable JVM TI or aspects of JVM TI, this is handled programmatically by the use of capabilities.

Agent Start-Up

The VM starts each agent by invoking a start-up function. If the agent is started in the OnLoad phase the function Agent_OnLoad or Agent_OnLoad_L for statically linked agents will be invoked. If the agent is started in the live phase the function Agent_OnAttach or Agent_OnAttach_L for statically linked agents will be invoked. Exactly one call to a start-up function is made per agent.

Agent Start-Up (OnLoad phase)

If an agent is started during the OnLoad phase then its agent library must export a start-up function with the following prototype: 
JNIEXPORT jint JNICALL
Agent_OnLoad(JavaVM *vm, char *options, void *reserved)
Or for a statically linked agent named 'L': 
JNIEXPORT jint JNICALL
Agent_OnLoad_L(JavaVM *vm, char *options, void *reserved)
The VM will start the agent by calling this function. It will be called early enough in VM initialization that:
The VM will call the Agent_OnLoad or Agent_OnLoad_<agent-lib-name> function with <options> as the second argument - that is, using the command-line option examples, "opt1,opt2" will be passed to the char *options argument of Agent_OnLoad. The options argument is encoded as a modified UTF-8 string. If =<options> is not specified, a zero length string is passed to options. The lifespan of the options string is the Agent_OnLoad or Agent_OnLoad_<agent-lib-name> call. If needed beyond this time the string or parts of the string must be copied. The period between when Agent_OnLoad is called and when it returns is called the OnLoad phase. Since the VM is not initialized during the OnLoad phase, the set of allowed operations inside Agent_OnLoad is restricted (see the function descriptions for the functionality available at this time). The agent can safely process the options and set event callbacks with SetEventCallbacks. Once the VM initialization event is received (that is, the VMInit callback is invoked), the agent can complete its initialization.

Rationale: Early startup is required so that agents can set the desired capabilities, many of which must be set before the VM is initialized. In JVMDI, the -Xdebug command-line option provided very coarse-grain control of capabilities. JVMPI implementations use various tricks to provide a single "JVMPI on" switch. No reasonable command-line option could provide the fine-grain of control required to balance needed capabilities vs performance impact. Early startup is also needed so that agents can control the execution environment - modifying the file system and system properties to install their functionality.

The return value from Agent_OnLoad or Agent_OnLoad_<agent-lib-name> is used to indicate an error. Any value other than zero indicates an error and causes termination of the VM.

Agent Start-Up (Live phase)

A VM may support a mechanism that allows agents to be started in the VM during the live phase. The details of how this is supported, are implementation specific. For example, a tool may use some platform specific mechanism, or implementation specific API, to attach to the running VM, and request it start a given agent.
The VM prints a warning on the standard error stream for each agent that it attempts to start in the live phase. If an agent was previously started (in the OnLoad phase or in the live phase), then it is implementation specific as to whether a warning is printed when attempting to start the same agent a second or subsequent time. Warnings can be disabled by means of an implementation-specific command line option.
Implementation Note: For the HotSpot VM, the VM option -XX:+EnableDynamicAgentLoading is used to opt-in to allow dynamic loading of agents in the live phase. This option suppresses the warning to standard error when starting an agent in the live phase.
If an agent is started during the live phase then its agent library must export a start-up function with the following prototype: 
JNIEXPORT jint JNICALL
Agent_OnAttach(JavaVM* vm, char *options, void *reserved)
Or for a statically linked agent named 'L': 
JNIEXPORT jint JNICALL
Agent_OnAttach_L(JavaVM* vm, char *options, void *reserved)
The VM will start the agent by calling this function. It will be called in the context of a thread that is attached to the VM. The first argument <vm> is the Java VM. The <options> argument is the startup options provided to the agent. <options> is encoded as a modified UTF-8 string. If startup options were not provided, a zero length string is passed to options. The lifespan of the options string is the Agent_OnAttach or Agent_OnAttach_<agent-lib-name> call. If needed beyond this time the string or parts of the string must be copied.
Note that some capabilities may not be available in the live phase.
The Agent_OnAttach or Agent_OnAttach_<agent-lib-name > function initializes the agent and returns a value to the VM to indicate if an error occurred. Any value other than zero indicates an error. An error does not cause the VM to terminate. Instead the VM ignores the error, or takes some implementation specific action -- for example it might print an error to standard error, or record the error in a system log.

Agent Shutdown

The library may optionally export a shutdown function with the following prototype: 
JNIEXPORT void JNICALL
Agent_OnUnload(JavaVM *vm)
Or for a statically linked agent named 'L': 
JNIEXPORT void JNICALL
Agent_OnUnload_L(JavaVM *vm)
This function will be called by the VM when the library is about to be unloaded. The library will be unloaded (unless it is statically linked into the executable) and this function will be called if some platform specific mechanism causes the unload (an unload mechanism is not specified in this document) or the library is (in effect) unloaded by the termination of the VM. VM termination includes normal termination and VM failure, including start-up failure, but not, of course, uncontrolled shutdown. An implementation may also choose to not call this function if the Agent_OnAttach/ Agent_OnAttach_L function reported an error (returned a non-zero value). Note the distinction between this function and the VM Death event: for the VM Death event to be sent, the VM must have run at least to the point of initialization and a valid JVM TI environment must exist which has set a callback for VMDeath and enabled the event. None of these are required for Agent_OnUnload or Agent_OnUnload_<agent-lib-name> and this function is also called if the library is unloaded for other reasons. In the case that a VM Death event is sent, it will be sent before this function is called (assuming this function is called due to VM termination). This function can be used to clean-up resources allocated by the agent.

JAVA_TOOL_OPTIONS

Since the command-line cannot always be accessed or modified, for example in embedded VMs or simply VMs launched deep within scripts, a JAVA_TOOL_OPTIONS variable is provided so that agents may be launched in these cases.
Platforms which support environment variables or other named strings, may support the JAVA_TOOL_OPTIONS variable. This variable will be broken into options at white-space boundaries. White-space characters include space, tab, carriage-return, new-line, vertical-tab, and form-feed. Sequences of white-space characters are considered equivalent to a single white-space character. No white-space is included in the options unless quoted. Quoting is as follows: JNI_CreateJavaVM (in the JNI Invocation API) will prepend these options to the options supplied in its JavaVMInitArgs argument. Note that module related options must be expressed in their "option=value" format (note the required '=' between "option" and "value") for JNI_CreateJavaVM to process them correctly.
Platforms may disable this feature in cases where security is a concern; for example, the Reference Implementation disables this feature on Unix systems when the effective user or group ID differs from the real ID. This feature is intended to support the initialization of tools -- specifically including the launching of native or Java programming language agents. Multiple tools may wish to use this feature, so the variable should not be overwritten, instead, options should be appended to the variable. Note that since the variable is processed at the time of the JNI Invocation API create VM call, options processed by a launcher (e.g., VM selection options) will not be handled.

Environments

The JVM TI specification supports the use of multiple simultaneous JVM TI agents. Each agent has its own JVM TI environment. That is, the JVM TI state is separate for each agent - changes to one environment do not affect the others. The state of a JVM TI environment includes: Although their JVM TI state is separate, agents inspect and modify the shared state of the VM, they also share the native environment in which they execute. As such, an agent can perturb the results of other agents or cause them to fail. It is the responsibility of the agent writer to specify the level of compatibility with other agents. JVM TI implementations are not capable of preventing destructive interactions between agents. Techniques to reduce the likelihood of these occurrences are beyond the scope of this document.
An agent creates a JVM TI environment by passing a JVM TI version as the interface ID to the JNI Invocation API function GetEnv. See Accessing JVM TI Functions for more details on the creation and use of JVM TI environments. Typically, JVM TI environments are created by calling GetEnv from Agent_OnLoad.

Bytecode Instrumentation

This interface does not include some events that one might expect in an interface with profiling support. Some examples include full speed method enter and exit events. The interface instead provides support for bytecode instrumentation, the ability to alter the Java virtual machine bytecode instructions which comprise the target program. Typically, these alterations are to add "events" to the code of a method - for example, to add, at the beginning of a method, a call to MyProfiler.methodEntered(). Since the changes are purely additive, they do not modify application state or behavior. Because the inserted agent code is standard bytecodes, the VM can run at full speed, optimizing not only the target program but also the instrumentation. If the instrumentation does not involve switching from bytecode execution, no expensive state transitions are needed. The result is high performance events. This approach also provides complete control to the agent: instrumentation can be restricted to "interesting" portions of the code (e.g., the end user's code) and can be conditional. Instrumentation can run entirely in Java programming language code or can call into the native agent. Instrumentation can simply maintain counters or can statistically sample events.
Instrumentation can be inserted in one of three ways:
The class modification functionality provided in this interface is intended to provide a mechanism for instrumentation (the ClassFileLoadHook event and the RetransformClasses function) and, during development, for fix-and-continue debugging (the RedefineClasses function).
Care must be taken to avoid perturbing dependencies, especially when instrumenting core classes. For example, an approach to getting notification of every object allocation is to instrument the constructor on Object. Assuming that the constructor is initially empty, the constructor could be changed to: 
      public Object() {
        MyProfiler.allocationTracker(this);
      }
However, if this change was made using the ClassFileLoadHook event then this might impact a typical VM as follows: the first created object will call the constructor causing a class load of MyProfiler; which will then cause object creation, and since MyProfiler isn't loaded yet, infinite recursion; resulting in a stack overflow. A refinement of this would be to delay invoking the tracking method until a safe time. For example, trackAllocations could be set in the handler for the VMInit event. 
      static boolean trackAllocations = false;

      public Object() {
        if (trackAllocations) {
          MyProfiler.allocationTracker(this);
        }
      }
The SetNativeMethodPrefix allows native methods to be instrumented by the use of wrapper methods.

Bytecode Instrumentation of code in modules

Agents can use the functions AddModuleReads, AddModuleExports, AddModuleOpens, AddModuleUses and AddModuleProvides to update a module to expand the set of modules that it reads, the set of packages that it exports or opens to other modules, or the services that it uses and provides.
As an aid to agents that deploy supporting classes on the search path of the bootstrap class loader, or the search path of the class loader that loads the main class, the Java virtual machine arranges for the module of classes transformed by the ClassFileLoadHook event to read the unnamed module of both class loaders.

Modified UTF-8 String Encoding

JVM TI uses modified UTF-8 to encode character strings. This is the same encoding used by JNI. Modified UTF-8 differs from standard UTF-8 in the representation of supplementary characters and of the null character. See the Modified UTF-8 Strings section of the JNI specification for details.

Specification Context

Since this interface provides access to the state of applications running in the Java virtual machine; terminology refers to the Java platform and not the native platform (unless stated otherwise). For example:
Sun, Sun Microsystems, the Sun logo, Java, and JVM are trademarks or registered trademarks of Oracle and/or its affiliates, in the U.S. and other countries.

Functions

Accessing Functions

Native code accesses JVM TI features by calling JVM TI functions. Access to JVM TI functions is by use of an interface pointer in the same manner as Java Native Interface (JNI) functions are accessed. The JVM TI interface pointer is called the environment pointer.
An environment pointer is a pointer to an environment and has the type jvmtiEnv*. An environment has information about its JVM TI connection. The first value in the environment is a pointer to the function table. The function table is an array of pointers to JVM TI functions. Every function pointer is at a predefined offset inside the array.
When used from the C language: double indirection is used to access the functions; the environment pointer provides context and is the first parameter of each function call; for example: 
jvmtiEnv *jvmti;
...
jvmtiError err = (*jvmti)->GetLoadedClasses(jvmti, &class_count, &classes);
When used from the C++ language: functions are accessed as member functions of jvmtiEnv; the environment pointer is not passed to the function call; for example: 
jvmtiEnv *jvmti;
...
jvmtiError err = jvmti->GetLoadedClasses(&class_count, &classes);
Unless otherwise stated, all examples and declarations in this specification use the C language.
A JVM TI environment can be obtained through the JNI Invocation API GetEnv function: 
jvmtiEnv *jvmti;
...
(*jvm)->GetEnv(jvm, &jvmti, JVMTI_VERSION_1_0);
Each call to GetEnv creates a new JVM TI connection and thus a new JVM TI environment. The version argument of GetEnv must be a JVM TI version. The returned environment may have a different version than the requested version but the returned environment must be compatible. GetEnv will return JNI_EVERSION if a compatible version is not available, if JVM TI is not supported or JVM TI is not supported in the current VM configuration. Other interfaces may be added for creating JVM TI environments in specific contexts. Each environment has its own state (for example, desired events, event handling functions, and capabilities). An environment is released with DisposeEnvironment. Thus, unlike JNI which has one environment per thread, JVM TI environments work across threads and are created dynamically.

Null Pointers

Parts of this specification refer to a "null pointer" as a possible function parameter or return value. A "null pointer" is C NULL or C++ nullptr.

Function Return Values

JVM TI functions always return an error code via the jvmtiError function return value. Some functions can return additional values through pointers provided by the calling function. In some cases, JVM TI functions allocate memory that your program must explicitly deallocate. This is indicated in the individual JVM TI function descriptions. Empty lists, arrays, sequences, etc are returned as a null pointer.
In the event that the JVM TI function encounters an error (any return value other than JVMTI_ERROR_NONE) the values of memory referenced by argument pointers is undefined, but no memory will have been allocated and no global references will have been allocated. If the error occurs because of invalid input, no action will have occurred.

Managing JNI Object References

JVM TI functions identify objects with JNI references (jobject and jclass) and their derivatives (jthread and jthreadGroup). References passed to JVM TI functions can be either global or local, but they must be strong references. All references returned by JVM TI functions are local references--these local references are created during the JVM TI call. Local references are a resource that must be managed (see the JNI Documentation). When threads return from native code all local references are freed. Note that some threads, including typical agent threads, will never return from native code. A thread is ensured the ability to create sixteen local references without the need for any explicit management. For threads executing a limited number of JVM TI calls before returning from native code (for example, threads processing events), it may be determined that no explicit management is needed. However, long running agent threads will need explicit local reference management--usually with the JNI functions PushLocalFrame and PopLocalFrame. Conversely, to preserve references beyond the return from native code, they must be converted to global references. These rules do not apply to jmethodID and jfieldID as they are not jobjects.

Prerequisite State for Calling Functions

Unless the function explicitly states that the agent must bring a thread or the VM to a particular state (for example, suspended), the JVM TI implementation is responsible for bringing the VM to a safe and consistent state for performing the function.

Exceptions and Functions

JVM TI functions never throw exceptions; error conditions are communicated via the function return value. Any existing exception state is preserved across a call to a JVM TI function. See the Java Exceptions section of the JNI specification for information on handling exceptions.

Function Index

Memory Management

Memory Management functions: These functions provide for the allocation and deallocation of memory used by JVM TI functionality and can be used to provide working memory for agents. Memory managed by JVM TI is not compatible with other memory allocation libraries and mechanisms.

Allocate

jvmtiError
Allocate(jvmtiEnv* env,
            jlong size,
            unsigned char** mem_ptr)
Allocate an area of memory through the JVM TI allocator. The allocated memory should be freed with Deallocate.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
46
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
sizejlong The number of bytes to allocate.

Rationale: jlong is used for compatibility with JVMDI.

mem_ptrunsigned char** On return, a pointer to the beginning of the allocated memory. If size is zero, a null pointer is returned.
Agent passes a pointer to a unsigned char*. On return, the unsigned char* points to a newly allocated array of size size. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_OUT_OF_MEMORY Memory request cannot be honored.
JVMTI_ERROR_ILLEGAL_ARGUMENT size is less than zero.
JVMTI_ERROR_NULL_POINTER mem_ptr is a null pointer .

Deallocate

jvmtiError
Deallocate(jvmtiEnv* env,
            unsigned char* mem)
Deallocate mem using the JVM TI allocator. This function should be used to deallocate any memory allocated and returned by a JVM TI function (including memory allocated with Allocate). All allocated memory must be deallocated or the memory cannot be reclaimed.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
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1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
mem unsigned char * A pointer to the beginning of the allocated memory. Please ignore "On return, the elements are set."
Agent passes an array of unsigned char. The incoming values of the elements of the array are ignored. On return, the elements are set. If mem is null pointer, the call is ignored.
Errors
This function returns a universal error

Thread

Thread functions: Thread function types: Thread types: Thread flags and constants: These functions provide information about threads and allow an agent to suspend and resume threads.
The jthread specified to these functions can be a JNI reference to a platform thread or virtual thread. Some functions are not supported on virtual threads and return JVMTI_ERROR_UNSUPPORTED_OPERATION when called with a reference to a virtual thread.

Get Thread State

jvmtiError
GetThreadState(jvmtiEnv* env,
            jthread thread,
            jint* thread_state_ptr)
Get the state of a thread. The state of the thread is represented by the answers to the hierarchical set of questions below:
The answers are represented by the following bit vector.
Thread State Flags
ConstantValueDescription
JVMTI_THREAD_STATE_ALIVE0x0001 Thread is alive. Zero if thread is new (not started) or terminated.
JVMTI_THREAD_STATE_TERMINATED0x0002 Thread has completed execution.
JVMTI_THREAD_STATE_RUNNABLE0x0004 Thread is runnable.
JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER0x0400 Thread is waiting to enter a synchronized block/method or, after an Object.wait(), waiting to re-enter a synchronized block/method.
JVMTI_THREAD_STATE_WAITING0x0080 Thread is waiting.
JVMTI_THREAD_STATE_WAITING_INDEFINITELY0x0010 Thread is waiting without a timeout. For example, Object.wait().
JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT0x0020 Thread is waiting with a maximum time to wait specified. For example, Object.wait(long).
JVMTI_THREAD_STATE_SLEEPING0x0040 Thread is sleeping -- Thread.sleep.
JVMTI_THREAD_STATE_IN_OBJECT_WAIT0x0100 Thread is waiting on an object monitor -- Object.wait.
JVMTI_THREAD_STATE_PARKED0x0200 Thread is parked, for example: LockSupport.park, LockSupport.parkUtil and LockSupport.parkNanos. A virtual thread that is sleeping, in Thread.sleep, may have this state flag set instead of JVMTI_THREAD_STATE_SLEEPING.
JVMTI_THREAD_STATE_SUSPENDED0x100000 Thread is suspended by a suspend function (such as SuspendThread). If this bit is set, the other bits refer to the thread state before suspension.
JVMTI_THREAD_STATE_INTERRUPTED0x200000 Thread has been interrupted.
JVMTI_THREAD_STATE_IN_NATIVE0x400000 Thread is in native code--that is, a native method is running which has not called back into the VM or Java programming language code.
This flag is not set when running VM compiled Java programming language code nor is it set when running VM code or VM support code. Native VM interface functions, such as JNI and JVM TI functions, may be implemented as VM code.
JVMTI_THREAD_STATE_VENDOR_10x10000000 Defined by VM vendor.
JVMTI_THREAD_STATE_VENDOR_20x20000000 Defined by VM vendor.
JVMTI_THREAD_STATE_VENDOR_30x40000000 Defined by VM vendor.
The following definitions are used to convert JVM TI thread state to java.lang.Thread.State style states.
java.lang.Thread.State Conversion Masks
ConstantValueDescription
JVMTI_JAVA_LANG_THREAD_STATE_MASKJVMTI_THREAD_STATE_TERMINATED | JVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_RUNNABLE | JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER | JVMTI_THREAD_STATE_WAITING | JVMTI_THREAD_STATE_WAITING_INDEFINITELY | JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT Mask the state with this before comparison
JVMTI_JAVA_LANG_THREAD_STATE_NEW0 java.lang.Thread.State.NEW
JVMTI_JAVA_LANG_THREAD_STATE_TERMINATEDJVMTI_THREAD_STATE_TERMINATED java.lang.Thread.State.TERMINATED
JVMTI_JAVA_LANG_THREAD_STATE_RUNNABLEJVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_RUNNABLE java.lang.Thread.State.RUNNABLE
JVMTI_JAVA_LANG_THREAD_STATE_BLOCKEDJVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER java.lang.Thread.State.BLOCKED
JVMTI_JAVA_LANG_THREAD_STATE_WAITINGJVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_WAITING | JVMTI_THREAD_STATE_WAITING_INDEFINITELY java.lang.Thread.State.WAITING
JVMTI_JAVA_LANG_THREAD_STATE_TIMED_WAITINGJVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_WAITING | JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT java.lang.Thread.State.TIMED_WAITING
Rules
There can be no more than one answer to a question, although there can be no answer (because the answer is unknown, does not apply, or none of the answers is correct). An answer is set only when the enclosing answers match. That is, no more than one of can be set (a J2SETM compliant implementation will always set one of these if JVMTI_THREAD_STATE_ALIVE is set). And if any of these are set, the enclosing answer JVMTI_THREAD_STATE_ALIVE is set. No more than one of can be set (a J2SETM compliant implementation will always set one of these if JVMTI_THREAD_STATE_WAITING is set). And if either is set, the enclosing answers JVMTI_THREAD_STATE_ALIVE and JVMTI_THREAD_STATE_WAITING are set. No more than one of can be set. And if any of these is set, the enclosing answers JVMTI_THREAD_STATE_ALIVE and JVMTI_THREAD_STATE_WAITING are set. Also, if JVMTI_THREAD_STATE_SLEEPING is set, then JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT is set. If a state A is implemented using the mechanism of state B then it is state A which is returned by this function. For example, if Thread.sleep(long) is implemented using Object.wait(long) then it is still JVMTI_THREAD_STATE_SLEEPING which is returned. More than one of can be set, but if any is set, JVMTI_THREAD_STATE_ALIVE is set.
And finally, JVMTI_THREAD_STATE_TERMINATED cannot be set unless JVMTI_THREAD_STATE_ALIVE is not set.
The thread state representation is designed for extension in future versions of the specification; thread state values should be used accordingly, that is they should not be used as ordinals. Most queries can be made by testing a single bit, if use in a switch statement is desired, the state bits should be masked with the interesting bits. All bits not defined above are reserved for future use. A VM, compliant to the current specification, must set reserved bits to zero. An agent should ignore reserved bits -- they should not be assumed to be zero and thus should not be included in comparisons.
Examples
Note that the values below exclude reserved and vendor bits.
The state of a thread blocked at a synchronized-statement would be: 
            JVMTI_THREAD_STATE_ALIVE + JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER
The state of a thread which hasn't started yet would be: 
            0
The state of a thread at a Object.wait(3000) would be: 
            JVMTI_THREAD_STATE_ALIVE + JVMTI_THREAD_STATE_WAITING +
                JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT +
                JVMTI_THREAD_STATE_IN_OBJECT_WAIT
The state of a thread suspended while runnable would be: 
            JVMTI_THREAD_STATE_ALIVE + JVMTI_THREAD_STATE_RUNNABLE + JVMTI_THREAD_STATE_SUSPENDED
Testing the State
In most cases, the thread state can be determined by testing the one bit corresponding to that question. For example, the code to test if a thread is sleeping: 
        jint state;
        jvmtiError err;

        err = (*jvmti)->GetThreadState(jvmti, thread, &state);
        if (err == JVMTI_ERROR_NONE) {
           if (state & JVMTI_THREAD_STATE_SLEEPING) {  ...
For waiting (that is, in Object.wait, parked, or sleeping) it would be: 
           if (state & JVMTI_THREAD_STATE_WAITING) {  ...
For some states, more than one bit will need to be tested as is the case when testing if a thread has not yet been started: 
           if ((state & (JVMTI_THREAD_STATE_ALIVE | JVMTI_THREAD_STATE_TERMINATED)) == 0)  {  ...
To distinguish timed from untimed Object.wait: 
           if (state & JVMTI_THREAD_STATE_IN_OBJECT_WAIT)  {
             if (state & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT)  {
               printf("in Object.wait(long timeout)\n");
             } else {
               printf("in Object.wait()\n");
             }
           }
Relationship to java.lang.Thread.State
The thread state represented by java.lang.Thread.State returned from java.lang.Thread.getState() is a subset of the information returned from this function. The corresponding java.lang.Thread.State can be determined by using the provided conversion masks. For example, this returns the name of the java.lang.Thread.State thread state: 
            err = (*jvmti)->GetThreadState(jvmti, thread, &state);
            abortOnError(err);
            switch (state & JVMTI_JAVA_LANG_THREAD_STATE_MASK) {
            case JVMTI_JAVA_LANG_THREAD_STATE_NEW:
              return "NEW";
            case JVMTI_JAVA_LANG_THREAD_STATE_TERMINATED:
              return "TERMINATED";
            case JVMTI_JAVA_LANG_THREAD_STATE_RUNNABLE:
              return "RUNNABLE";
            case JVMTI_JAVA_LANG_THREAD_STATE_BLOCKED:
              return "BLOCKED";
            case JVMTI_JAVA_LANG_THREAD_STATE_WAITING:
              return "WAITING";
            case JVMTI_JAVA_LANG_THREAD_STATE_TIMED_WAITING:
              return "TIMED_WAITING";
            }
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
17
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread The thread to query. If thread is null, the current thread is used.
thread_state_ptrjint* On return, points to state flags, as defined by the Thread State Flags.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_NULL_POINTER thread_state_ptr is a null pointer .

Get Current Thread

jvmtiError
GetCurrentThread(jvmtiEnv* env,
            jthread* thread_ptr)
Get the current thread. The current thread is the Java programming language thread which has called the function. The function may return a null pointer in the start phase if the can_generate_early_vmstart capability is enabled and the java.lang.Thread class has not been initialized yet.
Note that most JVM TI functions that take a thread as an argument will accept null to mean the current thread.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
18
1.1
Capabilities
Required Functionality
Parameters
NameTypeDescription
thread_ptrjthread* On return, points to the current thread, or null.
Agent passes a pointer to a jthread. On return, the jthread has been set. The object returned by thread_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER thread_ptr is a null pointer .

Get All Threads

jvmtiError
GetAllThreads(jvmtiEnv* env,
            jint* threads_count_ptr,
            jthread** threads_ptr)
Get all live platform threads that are attached to the VM. The list of threads includes agent threads. It does not include virtual threads. A thread is live if java.lang.Thread.isAlive() would return true, that is, the thread has been started and has not yet terminated. The universe of threads is determined by the context of the JVM TI environment, which typically is all threads attached to the VM.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
4
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threads_count_ptrjint* On return, points to the number of threads.
Agent passes a pointer to a jint. On return, the jint has been set.
threads_ptrjthread** On return, points to an array of references, one for each thread.
Agent passes a pointer to a jthread*. On return, the jthread* points to a newly allocated array of size *threads_count_ptr. The array should be freed with Deallocate. The objects returned by threads_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER threads_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER threads_ptr is a null pointer .

Suspend Thread

jvmtiError
SuspendThread(jvmtiEnv* env,
            jthread thread)
Suspend the specified thread. If the calling thread is specified, this function will not return until some other thread calls ResumeThread. If the thread is currently suspended, this function does nothing and returns an error.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
5
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_suspend Can suspend and resume threads
Parameters
NameTypeDescription
threadjthread The thread to suspend. If thread is null, the current thread is used.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_suspend. Use AddCapabilities.
JVMTI_ERROR_THREAD_SUSPENDED Thread already suspended.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Suspend Thread List

jvmtiError
SuspendThreadList(jvmtiEnv* env,
            jint request_count,
            const jthread* request_list,
            jvmtiError* results)
Suspend the request_count threads specified in the request_list array. Threads may be resumed with ResumeThreadList or ResumeThread. If the calling thread is specified in the request_list array, this function will not return until some other thread resumes it. Errors encountered in the suspension of a thread are returned in the results array, not in the return value of this function. Threads that are currently suspended do not change state.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
92
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_suspend Can suspend and resume threads
Parameters
NameTypeDescription
request_countjint The number of threads to suspend.
request_listconst jthread* The list of threads to suspend.
Agent passes in an array of request_count elements of jthread.
resultsjvmtiError* An agent supplied array of request_count elements. On return, filled with the error code for the suspend of the corresponding thread. The error code will be JVMTI_ERROR_NONE if the thread was suspended by this call. Possible error codes are those specified for SuspendThread.
Agent passes an array large enough to hold request_count elements of jvmtiError. The incoming values of the elements of the array are ignored. On return, the elements are set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_suspend. Use AddCapabilities.
JVMTI_ERROR_ILLEGAL_ARGUMENT request_count is less than 0.
JVMTI_ERROR_NULL_POINTER request_list is a null pointer .
JVMTI_ERROR_NULL_POINTER results is a null pointer .

Suspend All Virtual Threads

jvmtiError
SuspendAllVirtualThreads(jvmtiEnv* env,
            jint except_count,
            const jthread* except_list)
Suspend all virtual threads except those in the exception list. Virtual threads that are currently suspended do not change state. Virtual threads may be resumed with ResumeAllVirtualThreads or ResumeThreadList or ResumeThread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
118
21
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capabilities (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_suspend Can suspend and resume threads
can_support_virtual_threadsCan support virtual threads
Parameters
NameTypeDescription
except_countjint The number of threads in the list of threads not to be suspended.
except_listconst jthread * The list of threads not to be suspended.
Agent passes in an array of except_count elements of jthread. If except_list is null pointer, not an error if except_count == 0.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_suspend. Use AddCapabilities.
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_support_virtual_threads. Use AddCapabilities.
JVMTI_ERROR_INVALID_THREAD A thread in except_list was invalid.
JVMTI_ERROR_NULL_POINTER Both except_list was null and except_count was non-zero.
JVMTI_ERROR_ILLEGAL_ARGUMENT except_count is less than 0.

Resume Thread

jvmtiError
ResumeThread(jvmtiEnv* env,
            jthread thread)
Resume a suspended thread. Any threads currently suspended through a JVM TI suspend function (eg. SuspendThread) will resume execution; all other threads are unaffected.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
6
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_suspend Can suspend and resume threads
Parameters
NameTypeDescription
threadjthread The thread to resume.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_suspend. Use AddCapabilities.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended.
JVMTI_ERROR_INVALID_TYPESTATE The state of the thread has been modified, and is now inconsistent.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Resume Thread List

jvmtiError
ResumeThreadList(jvmtiEnv* env,
            jint request_count,
            const jthread* request_list,
            jvmtiError* results)
Resume the request_count threads specified in the request_list array. Any thread suspended through a JVM TI suspend function (eg. SuspendThreadList) will resume execution.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
93
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_suspend Can suspend and resume threads
Parameters
NameTypeDescription
request_countjint The number of threads to resume.
request_listconst jthread* The threads to resume.
Agent passes in an array of request_count elements of jthread.
resultsjvmtiError* An agent supplied array of request_count elements. On return, filled with the error code for the resume of the corresponding thread. The error code will be JVMTI_ERROR_NONE if the thread was suspended by this call. Possible error codes are those specified for ResumeThread.
Agent passes an array large enough to hold request_count elements of jvmtiError. The incoming values of the elements of the array are ignored. On return, the elements are set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_suspend. Use AddCapabilities.
JVMTI_ERROR_ILLEGAL_ARGUMENT request_count is less than 0.
JVMTI_ERROR_NULL_POINTER request_list is a null pointer .
JVMTI_ERROR_NULL_POINTER results is a null pointer .

Resume All Virtual Threads

jvmtiError
ResumeAllVirtualThreads(jvmtiEnv* env,
            jint except_count,
            const jthread* except_list)
Resume all virtual threads except those in the exception list. Virtual threads that are currently resumed do not change state. Virtual threads may be suspended with SuspendAllVirtualThreads or SuspendThreadList or SuspendThread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
119
21
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capabilities (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_suspend Can suspend and resume threads
can_support_virtual_threadsCan support virtual threads
Parameters
NameTypeDescription
except_countjint The number of threads in the list of threads not to be resumed.
except_listconst jthread * The list of threads not to be resumed.
Agent passes in an array of except_count elements of jthread. If except_list is null pointer, not an error if except_count == 0.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_suspend. Use AddCapabilities.
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_support_virtual_threads. Use AddCapabilities.
JVMTI_ERROR_INVALID_THREAD A thread in except_list was invalid.
JVMTI_ERROR_NULL_POINTER Both except_list was null and except_count was non-zero.
JVMTI_ERROR_ILLEGAL_ARGUMENT except_count is less than 0.

Stop Thread

jvmtiError
StopThread(jvmtiEnv* env,
            jthread thread,
            jobject exception)
Send the specified asynchronous exception to the specified thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
7
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_signal_thread Can send stop or interrupt to threads
Parameters
NameTypeDescription
threadjthread The thread to stop. The StopThread function may be used to send an asynchronous exception to a virtual thread when it is suspended at an event. An implementation may support sending an asynchronous exception to a suspended virtual thread in other cases.
exceptionjobject The asynchronous exception object.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_signal_thread. Use AddCapabilities.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread is a virtual thread and was not suspended and was not the current thread.
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation was unable to throw an asynchronous exception from the current frame.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_INVALID_OBJECT exception is not an object.

Interrupt Thread

jvmtiError
InterruptThread(jvmtiEnv* env,
            jthread thread)
Interrupt the specified thread (similar to java.lang.Thread.interrupt).
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
8
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_signal_thread Can send stop or interrupt to threads
Parameters
NameTypeDescription
threadjthread The thread to interrupt.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_signal_thread. Use AddCapabilities.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Get Thread Info

typedef struct {
    char* name;
    jint priority;
    jboolean is_daemon;
    jthreadGroup thread_group;
    jobject context_class_loader;
} jvmtiThreadInfo;
jvmtiError
GetThreadInfo(jvmtiEnv* env,
            jthread thread,
            jvmtiThreadInfo* info_ptr)
Get thread information. The fields of the jvmtiThreadInfo structure are filled in with details of the specified thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
9
1.0
Capabilities
Required Functionality

jvmtiThreadInfo - Thread information structure
FieldTypeDescription
namechar* The thread name, encoded as a modified UTF-8 string.
priorityjint The thread priority. See the thread priority constants: jvmtiThreadPriority. The priority of a virtual thread is always JVMTI_THREAD_NORM_PRIORITY.
is_daemonjboolean Is this a daemon thread? The daemon status of a virtual thread is always JNI_TRUE.
thread_groupjthreadGroup The thread group to which this thread belongs. Null if the thread has terminated.
context_class_loaderjobject The context class loader associated with this thread.
Parameters
NameTypeDescription
threadjthread The thread to query. If thread is null, the current thread is used.
info_ptrjvmtiThreadInfo* On return, filled with information describing the specified thread.
Agent passes a pointer to a jvmtiThreadInfo. On return, the jvmtiThreadInfo has been set. The pointer returned in the field name of jvmtiThreadInfo is a newly allocated array. The array should be freed with Deallocate. The object returned in the field thread_group of jvmtiThreadInfo is a JNI local reference and must be managed. The object returned in the field context_class_loader of jvmtiThreadInfo is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_NULL_POINTER info_ptr is a null pointer .

Get Owned Monitor Info

jvmtiError
GetOwnedMonitorInfo(jvmtiEnv* env,
            jthread thread,
            jint* owned_monitor_count_ptr,
            jobject** owned_monitors_ptr)
Get information about the monitors owned by the specified thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
10
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_owned_monitor_info Can get information about ownership of monitors - GetOwnedMonitorInfo
Parameters
NameTypeDescription
threadjthread The thread to query. If thread is null, the current thread is used.
owned_monitor_count_ptrjint* The number of monitors returned.
Agent passes a pointer to a jint. On return, the jint has been set.
owned_monitors_ptrjobject** The array of owned monitors.
Agent passes a pointer to a jobject*. On return, the jobject* points to a newly allocated array of size *owned_monitor_count_ptr. The array should be freed with Deallocate. The objects returned by owned_monitors_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_owned_monitor_info. Use AddCapabilities.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_NULL_POINTER owned_monitor_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER owned_monitors_ptr is a null pointer .

Get Owned Monitor Stack Depth Info

typedef struct {
    jobject monitor;
    jint stack_depth;
} jvmtiMonitorStackDepthInfo;
jvmtiError
GetOwnedMonitorStackDepthInfo(jvmtiEnv* env,
            jthread thread,
            jint* monitor_info_count_ptr,
            jvmtiMonitorStackDepthInfo** monitor_info_ptr)
Get information about the monitors owned by the specified thread and the depth of the stack frame which locked them.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
153
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_owned_monitor_stack_depth_info Can get information about owned monitors with stack depth - GetOwnedMonitorStackDepthInfo

jvmtiMonitorStackDepthInfo - Monitor stack depth information structure
FieldTypeDescription
monitorjobject The owned monitor.
stack_depthjint The stack depth. Corresponds to the stack depth used in the Stack Frame functions. That is, zero is the current frame, one is the frame which called the current frame. And it is negative one if the implementation cannot determine the stack depth (e.g., for monitors acquired by JNI MonitorEnter).
Parameters
NameTypeDescription
threadjthread The thread to query. If thread is null, the current thread is used.
monitor_info_count_ptrjint* The number of monitors returned.
Agent passes a pointer to a jint. On return, the jint has been set.
monitor_info_ptr jvmtiMonitorStackDepthInfo ** The array of owned monitor depth information.
Agent passes a pointer to a jvmtiMonitorStackDepthInfo*. On return, the jvmtiMonitorStackDepthInfo* points to a newly allocated array of size *monitor_info_count_ptr. The array should be freed with Deallocate. The objects returned in the field monitor of jvmtiMonitorStackDepthInfo are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_owned_monitor_stack_depth_info. Use AddCapabilities.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_NULL_POINTER monitor_info_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER monitor_info_ptr is a null pointer .

Get Current Contended Monitor

jvmtiError
GetCurrentContendedMonitor(jvmtiEnv* env,
            jthread thread,
            jobject* monitor_ptr)
Get the object, if any, whose monitor the specified thread is waiting to enter or waiting to regain through java.lang.Object.wait.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
11
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_current_contended_monitor Can GetCurrentContendedMonitor
Parameters
NameTypeDescription
threadjthread The thread to query. If thread is null, the current thread is used.
monitor_ptrjobject* On return, filled with the current contended monitor, or null if there is none.
Agent passes a pointer to a jobject. On return, the jobject has been set. The object returned by monitor_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_current_contended_monitor. Use AddCapabilities.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_NULL_POINTER monitor_ptr is a null pointer .

Agent Start Function

typedef void (JNICALL *jvmtiStartFunction)
    (jvmtiEnv* jvmti_env,
     JNIEnv* jni_env,
     void* arg);
Agent supplied callback function. This function is the entry point for an agent thread started with RunAgentThread.
Parameters
NameTypeDescription
jvmti_env jvmtiEnv * The JVM TI environment.
jni_env JNIEnv * The JNI environment.
arg void * The arg parameter passed to RunAgentThread.

Run Agent Thread

jvmtiError
RunAgentThread(jvmtiEnv* env,
            jthread thread,
            jvmtiStartFunction proc,
            const void* arg,
            jint priority)
Starts the execution of an agent thread. with the specified native function. The parameter arg is forwarded on to the start function (specified with proc) as its single argument. This function allows the creation of agent threads for handling communication with another process or for handling events without the need to load a special subclass of java.lang.Thread or implementer of java.lang.Runnable. Instead, the created thread can run entirely in native code. However, the created thread does require a newly created instance of java.lang.Thread (referenced by the argument thread) to which it will be associated. The thread object can be created with JNI calls.
The following common thread priorities are provided for your convenience:
Thread Priority Constants
ConstantValueDescription
JVMTI_THREAD_MIN_PRIORITY1 Minimum possible thread priority
JVMTI_THREAD_NORM_PRIORITY5 Normal thread priority
JVMTI_THREAD_MAX_PRIORITY10 Maximum possible thread priority
The new thread is started as a daemon thread with the specified priority. If enabled, a ThreadStart event will be sent.
Since the thread has been started, the thread will be live when this function returns, unless the thread terminated immediately.
The thread group of the thread is ignored -- specifically, the thread is not added to the thread group and the thread is not seen on queries of the thread group at either the Java programming language or JVM TI levels.
The thread is not visible to Java programming language queries but is included in JVM TI queries (for example, GetAllThreads and GetAllStackTraces).
Upon execution of proc, the new thread will be attached to the VM -- see the JNI documentation on Attaching to the VM.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
12
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread The thread to run. The thread may not be a virtual thread. Otherwise, the error code JVMTI_ERROR_UNSUPPORTED_OPERATION will be returned.
proc jvmtiStartFunction The start function.
argconst void * The argument to the start function.
Agent passes in a pointer. If arg is null pointer, A null pointer is passed to the start function.
priorityjint The priority of the started thread. Any thread priority allowed by java.lang.Thread.setPriority can be used including those in jvmtiThreadPriority.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_PRIORITY priority is less than JVMTI_THREAD_MIN_PRIORITY or greater than JVMTI_THREAD_MAX_PRIORITY
JVMTI_ERROR_UNSUPPORTED_OPERATION thread is a virtual thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_NULL_POINTER proc is a null pointer .

Set Thread Local Storage

jvmtiError
SetThreadLocalStorage(jvmtiEnv* env,
            jthread thread,
            const void* data)
The VM stores a pointer value associated with each environment-thread pair. This pointer value is called thread-local storage. This value is null unless set with this function. Agents can allocate memory in which they store thread specific information. By setting thread-local storage it can then be accessed with GetThreadLocalStorage.
This function is called by the agent to set the value of the JVM TI thread-local storage. JVM TI supplies to the agent a pointer-size thread-local storage that can be used to record per-thread information.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
103
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread Store to this thread. If thread is null, the current thread is used.
dataconst void * The value to be entered into the thread-local storage.
Agent passes in a pointer. If data is null pointer, value is set to null.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Get Thread Local Storage

jvmtiError
GetThreadLocalStorage(jvmtiEnv* env,
            jthread thread,
            void** data_ptr)
Called by the agent to get the value of the JVM TI thread-local storage.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
102
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread Retrieve from this thread. If thread is null, the current thread is used.
data_ptrvoid** Pointer through which the value of the thread local storage is returned. If thread-local storage has not been set with SetThreadLocalStorage the returned pointer is null.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_NULL_POINTER data_ptr is a null pointer .

Thread Group

Thread Group functions: Thread Group types:

Get Top Thread Groups

jvmtiError
GetTopThreadGroups(jvmtiEnv* env,
            jint* group_count_ptr,
            jthreadGroup** groups_ptr)
Return all top-level (parentless) thread groups in the VM.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
13
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
group_count_ptrjint* On return, points to the number of top-level thread groups.
Agent passes a pointer to a jint. On return, the jint has been set.
groups_ptrjthreadGroup** On return, refers to a pointer to the top-level thread group array.
Agent passes a pointer to a jthreadGroup*. On return, the jthreadGroup* points to a newly allocated array of size *group_count_ptr. The array should be freed with Deallocate. The objects returned by groups_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER group_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER groups_ptr is a null pointer .

Get Thread Group Info

typedef struct {
    jthreadGroup parent;
    char* name;
    jint max_priority;
    jboolean is_daemon;
} jvmtiThreadGroupInfo;
jvmtiError
GetThreadGroupInfo(jvmtiEnv* env,
            jthreadGroup group,
            jvmtiThreadGroupInfo* info_ptr)
Get information about the thread group. The fields of the jvmtiThreadGroupInfo structure are filled in with details of the specified thread group.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
14
1.0
Capabilities
Required Functionality

jvmtiThreadGroupInfo - Thread group information structure
FieldTypeDescription
parentjthreadGroup The parent thread group.
namechar* The thread group's name, encoded as a modified UTF-8 string.
max_priorityjint The maximum priority for this thread group.
is_daemonjboolean Is this a daemon thread group?
Parameters
NameTypeDescription
groupjthreadGroup The thread group to query.
info_ptrjvmtiThreadGroupInfo* On return, filled with information describing the specified thread group.
Agent passes a pointer to a jvmtiThreadGroupInfo. On return, the jvmtiThreadGroupInfo has been set. The object returned in the field parent of jvmtiThreadGroupInfo is a JNI local reference and must be managed. The pointer returned in the field name of jvmtiThreadGroupInfo is a newly allocated array. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD_GROUP group is not a thread group object.
JVMTI_ERROR_NULL_POINTER info_ptr is a null pointer .

Get Thread Group Children

jvmtiError
GetThreadGroupChildren(jvmtiEnv* env,
            jthreadGroup group,
            jint* thread_count_ptr,
            jthread** threads_ptr,
            jint* group_count_ptr,
            jthreadGroup** groups_ptr)
Get the live platform threads and the child thread groups in this thread group. Virtual threads are not returned by this function.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
15
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
groupjthreadGroup The group to query.
thread_count_ptrjint* On return, points to the number of live threads in this thread group.
Agent passes a pointer to a jint. On return, the jint has been set.
threads_ptrjthread** On return, points to an array of the live threads in this thread group.
Agent passes a pointer to a jthread*. On return, the jthread* points to a newly allocated array of size *thread_count_ptr. The array should be freed with Deallocate. The objects returned by threads_ptr are JNI local references and must be managed.
group_count_ptrjint* On return, points to the number of child thread groups
Agent passes a pointer to a jint. On return, the jint has been set.
groups_ptrjthreadGroup** On return, points to an array of the child thread groups.
Agent passes a pointer to a jthreadGroup*. On return, the jthreadGroup* points to a newly allocated array of size *group_count_ptr. The array should be freed with Deallocate. The objects returned by groups_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD_GROUP group is not a thread group object.
JVMTI_ERROR_NULL_POINTER thread_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER threads_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER group_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER groups_ptr is a null pointer .

Stack Frame

Stack Frame functions: Stack Frame types: These functions provide information about the stack of a thread. Stack frames are referenced by depth. The frame at depth zero is the current frame.
Stack frames are as described in The Java™ Virtual Machine Specification, Chapter 3.6, That is, they correspond to method invocations (including native methods) but do not correspond to platform native or VM internal frames.
A JVM TI implementation may use method invocations to launch a thread and the corresponding frames may be included in the stack as presented by these functions -- that is, there may be frames shown deeper than main() and run(). However this presentation must be consistent across all JVM TI functionality which uses stack frames or stack depth.

Stack frame information structure

Information about a stack frame is returned in this structure. 
typedef struct {
    jmethodID method;
    jlocation location;
} jvmtiFrameInfo;
jvmtiFrameInfo - Stack frame information structure
FieldTypeDescription
methodjmethodID The method executing in this frame.
locationjlocation The index of the instruction executing in this frame. -1 if the frame is executing a native method.

Stack information structure

Information about a set of stack frames is returned in this structure. 
typedef struct {
    jthread thread;
    jint state;
    jvmtiFrameInfo* frame_buffer;
    jint frame_count;
} jvmtiStackInfo;
jvmtiStackInfo - Stack information structure
FieldTypeDescription
threadjthread On return, the thread traced.
statejint On return, the thread state. See GetThreadState.
frame_buffer jvmtiFrameInfo * On return, this agent allocated buffer is filled with stack frame information.
frame_countjint On return, the number of records filled into frame_buffer. This will be min(max_frame_count, stackDepth).

Get Stack Trace

jvmtiError
GetStackTrace(jvmtiEnv* env,
            jthread thread,
            jint start_depth,
            jint max_frame_count,
            jvmtiFrameInfo* frame_buffer,
            jint* count_ptr)
Get information about the stack of a thread. If max_frame_count is less than the depth of the stack, the max_frame_count topmost frames are returned, otherwise the entire stack is returned. The topmost frames, those most recently invoked, are at the beginning of the returned buffer.
The following example causes up to five of the topmost frames to be returned and (if there are any frames) the currently executing method name to be printed. 
jvmtiFrameInfo frames[5];
jint count;
jvmtiError err;

err = (*jvmti)->GetStackTrace(jvmti, aThread, 0, 5,
                               frames, &count);
if (err == JVMTI_ERROR_NONE && count >= 1) {
   char *methodName;
   err = (*jvmti)->GetMethodName(jvmti, frames[0].method,
                       &methodName, NULL, NULL);
   if (err == JVMTI_ERROR_NONE) {
      printf("Executing method: %s", methodName);
   }
}
The thread need not be suspended to call this function.
The GetLineNumberTable function can be used to map locations to line numbers. Note that this mapping can be done lazily.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
104
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread Fetch the stack trace of this thread. If thread is null, the current thread is used.
start_depthjint Begin retrieving frames at this depth. If non-negative, count from the current frame, the first frame retrieved is at depth start_depth. For example, if zero, start from the current frame; if one, start from the caller of the current frame; if two, start from the caller of the caller of the current frame; and so on. If negative, count from below the oldest frame, the first frame retrieved is at depth stackDepth + start_depth, where stackDepth is the count of frames on the stack. For example, if negative one, only the oldest frame is retrieved; if negative two, start from the frame called by the oldest frame.
max_frame_countjint The maximum number of jvmtiFrameInfo records to retrieve.
frame_buffer jvmtiFrameInfo * On return, this agent allocated buffer is filled with stack frame information.
Agent passes an array large enough to hold max_frame_count elements of jvmtiFrameInfo. The incoming values of the elements of the array are ignored. On return, *count_ptr of the elements are set.
count_ptrjint* On return, points to the number of records filled in. For non-negative start_depth, this will be min(max_frame_count, stackDepth - start_depth). For negative start_depth, this will be min(max_frame_count, -start_depth).
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_ILLEGAL_ARGUMENT start_depth is positive and greater than or equal to stackDepth. Or start_depth is negative and less than -stackDepth.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT max_frame_count is less than 0.
JVMTI_ERROR_NULL_POINTER frame_buffer is a null pointer .
JVMTI_ERROR_NULL_POINTER count_ptr is a null pointer .

Get All Stack Traces

jvmtiError
GetAllStackTraces(jvmtiEnv* env,
            jint max_frame_count,
            jvmtiStackInfo** stack_info_ptr,
            jint* thread_count_ptr)
Get the stack traces of all live platform threads attached to the VM. The list includes the stack traces of agent threads. It does not include the stack traces of virtual threads.
If max_frame_count is less than the depth of a stack, the max_frame_count topmost frames are returned for that thread, otherwise the entire stack is returned. The topmost frames, those most recently invoked, are at the beginning of the returned buffer.
All stacks are collected simultaneously, that is, no changes will occur to the thread state or stacks between the sampling of one thread and the next. The threads need not be suspended. 
jvmtiStackInfo *stack_info;
jint thread_count;
int ti;
jvmtiError err;

err = (*jvmti)->GetAllStackTraces(jvmti, MAX_FRAMES, &stack_info, &thread_count);
if (err != JVMTI_ERROR_NONE) {
   ...
}
for (ti = 0; ti < thread_count; ++ti) {
   jvmtiStackInfo *infop = &stack_info[ti];
   jthread thread = infop->thread;
   jint state = infop->state;
   jvmtiFrameInfo *frames = infop->frame_buffer;
   int fi;

   myThreadAndStatePrinter(thread, state);
   for (fi = 0; fi < infop->frame_count; fi++) {
      myFramePrinter(frames[fi].method, frames[fi].location);
   }
}
/* this one Deallocate call frees all data allocated by GetAllStackTraces */
err = (*jvmti)->Deallocate(jvmti, stack_info);
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
100
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
max_frame_countjint The maximum number of jvmtiFrameInfo records to retrieve per thread.
stack_info_ptr jvmtiStackInfo ** On return, this buffer is filled with stack information for each thread. The number of jvmtiStackInfo records is determined by thread_count_ptr.
Note that this buffer is allocated to include the jvmtiFrameInfo buffers pointed to by jvmtiStackInfo.frame_buffer. These buffers must not be separately deallocated.
Agent passes a pointer to a jvmtiStackInfo*. On return, the jvmtiStackInfo* points to a newly allocated array. The array should be freed with Deallocate. The objects returned in the field thread of jvmtiStackInfo are JNI local references and must be managed.
thread_count_ptrjint* The number of threads traced.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_ILLEGAL_ARGUMENT max_frame_count is less than 0.
JVMTI_ERROR_NULL_POINTER stack_info_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER thread_count_ptr is a null pointer .

Get Thread List Stack Traces

jvmtiError
GetThreadListStackTraces(jvmtiEnv* env,
            jint thread_count,
            const jthread* thread_list,
            jint max_frame_count,
            jvmtiStackInfo** stack_info_ptr)
Get information about the stacks of the supplied threads. If max_frame_count is less than the depth of a stack, the max_frame_count topmost frames are returned for that thread, otherwise the entire stack is returned. The topmost frames, those most recently invoked, are at the beginning of the returned buffer.
All stacks are collected simultaneously, that is, no changes will occur to the thread state or stacks between the sampling one thread and the next. The threads need not be suspended.
If a thread has not yet started or terminates before the stack information is collected, a zero length stack (jvmtiStackInfo.frame_count will be zero) will be returned and the thread jvmtiStackInfo.state can be checked.
See the example for the similar function GetAllStackTraces.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
101
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
thread_countjint The number of threads to trace.
thread_listconst jthread* The list of threads to trace.
Agent passes in an array of thread_count elements of jthread.
max_frame_countjint The maximum number of jvmtiFrameInfo records to retrieve per thread.
stack_info_ptr jvmtiStackInfo ** On return, this buffer is filled with stack information for each thread. The number of jvmtiStackInfo records is determined by thread_count.
Note that this buffer is allocated to include the jvmtiFrameInfo buffers pointed to by jvmtiStackInfo.frame_buffer. These buffers must not be separately deallocated.
Agent passes a pointer to a jvmtiStackInfo*. On return, the jvmtiStackInfo* points to a newly allocated array of size *thread_count. The array should be freed with Deallocate. The objects returned in the field thread of jvmtiStackInfo are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD An element in thread_list is not a thread object.
JVMTI_ERROR_ILLEGAL_ARGUMENT thread_count is less than 0.
JVMTI_ERROR_NULL_POINTER thread_list is a null pointer .
JVMTI_ERROR_ILLEGAL_ARGUMENT max_frame_count is less than 0.
JVMTI_ERROR_NULL_POINTER stack_info_ptr is a null pointer .

Get Frame Count

jvmtiError
GetFrameCount(jvmtiEnv* env,
            jthread thread,
            jint* count_ptr)
Get the number of frames currently in the specified thread's call stack.
If this function is called for a thread actively executing bytecodes (for example, not the current thread and not suspended), the information returned is transient.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
16
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread The thread to query. If thread is null, the current thread is used.
count_ptrjint* On return, points to the number of frames in the call stack.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_NULL_POINTER count_ptr is a null pointer .

Pop Frame

jvmtiError
PopFrame(jvmtiEnv* env,
            jthread thread)
Pop the current frame of thread's stack. Popping a frame takes you to the previous frame. When the thread is resumed, the execution state of the thread is reset to the state immediately before the called method was invoked. That is (using The Java™ Virtual Machine Specification terminology): Note however, that any changes to the arguments, which occurred in the called method, remain; when execution continues, the first instruction to execute will be the invoke.
Between calling PopFrame and resuming the thread the state of the stack is undefined. To pop frames beyond the first, these three steps must be repeated:
A lock acquired by calling the called method (if it is a synchronized method) and locks acquired by entering synchronized blocks within the called method are released. Note: this does not apply to native locks or java.util.concurrent.locks locks.
Finally blocks are not executed.
Changes to global state are not addressed and thus remain changed.
The specified thread must be suspended or must be the current thread.
Both the called method and calling method must be non-native Java programming language methods.
No JVM TI events are generated by this function.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
80
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_pop_frame Can pop frames off the stack - PopFrame
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to be popped. The PopFrame function may be used to pop the current frame of a virtual thread when it is suspended at an event. An implementation may support popping the current frame of a suspended virtual thread in other cases.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_pop_frame. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Called or calling method is a native method. The implementation is unable to pop this frame.
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation was unable to pop the current frame.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are less than two stack frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Get Frame Location

jvmtiError
GetFrameLocation(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jmethodID* method_ptr,
            jlocation* location_ptr)
For a Java programming language frame, return the location of the instruction currently executing.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
19
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
threadjthread The thread of the frame to query. If thread is null, the current thread is used.
depthjint The depth of the frame to query.
method_ptrjmethodID* On return, points to the method for the current location.
Agent passes a pointer to a jmethodID. On return, the jmethodID has been set.
location_ptrjlocation* On return, points to the index of the currently executing instruction. Is set to -1 if the frame is executing a native method.
Agent passes a pointer to a jlocation. On return, the jlocation has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER method_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER location_ptr is a null pointer .

Notify Frame Pop

jvmtiError
NotifyFramePop(jvmtiEnv* env,
            jthread thread,
            jint depth)
When the frame that is currently at depth is popped from the stack, generate a FramePop event. See the FramePop event for details. Only frames corresponding to non-native Java programming language methods can receive notification.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
20
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_frame_pop_events Can set and thus get FramePop events
Parameters
NameTypeDescription
threadjthread The thread of the frame for which the frame pop event will be generated. If thread is null, the current thread is used.
depthjint The depth of the frame for which the frame pop event will be generated.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_frame_pop_events. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME The frame at depth is executing a native method.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.

Force Early Return

Force Early Return functions: These functions allow an agent to force a return from the current frame. The specified thread must be suspended or must be the current thread. These functions may be used to force a return from the current frame of a virtual thread when it is suspended at an event. An implementation may support forcing a return from the current frame of a suspended virtual thread in other cases. The method which will return early is referred to as the called method. The called method is the current method (as defined by The Java™ Virtual Machine Specification, Chapter 3.6) for the specified thread at the time the function is called.
The return occurs when execution of Java programming language code is resumed on this thread. Between calling one of these functions and resumption of thread execution, the state of the stack is undefined.
No further instructions are executed in the called method. Specifically, finally blocks are not executed. Note: this can cause inconsistent states in the application.
A lock acquired by calling the called method (if it is a synchronized method) and locks acquired by entering synchronized blocks within the called method are released. Note: this does not apply to native locks or java.util.concurrent.locks locks.
Events, such as MethodExit, are generated as they would be in a normal return.
The called method must be a non-native Java programming language method. Forcing return on a thread with only one frame on the stack causes the thread to exit when resumed.

Force Early Return - Object

jvmtiError
ForceEarlyReturnObject(jvmtiEnv* env,
            jthread thread,
            jobject value)
This function can be used to return from a method whose result type is Object or a subclass of Object.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
81
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_force_early_return Can return early from a method, as described in the Force Early Return category.
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to return early. If thread is null, the current thread is used.
valuejobject The return value for the called frame. An object or a null pointer.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_force_early_return. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Attempted to return early from a frame corresponding to a native method. The thread is a suspended virtual thread and the implementation was unable to force its current frame to return. Or the implementation is unable to provide this functionality on this frame.
JVMTI_ERROR_TYPE_MISMATCH The result type of the called method is not Object or a subclass of Object.
JVMTI_ERROR_TYPE_MISMATCH The supplied value is not compatible with the result type of the called method.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are no more frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_INVALID_OBJECT value is not an object.

Force Early Return - Int

jvmtiError
ForceEarlyReturnInt(jvmtiEnv* env,
            jthread thread,
            jint value)
This function can be used to return from a method whose result type is int, short, char, byte, or boolean.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
82
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_force_early_return Can return early from a method, as described in the Force Early Return category.
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to return early. If thread is null, the current thread is used.
valuejint The return value for the called frame.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_force_early_return. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Attempted to return early from a frame corresponding to a native method. The thread is a suspended virtual thread and the implementation was unable to force its current frame to return. Or the implementation is unable to provide this functionality on this frame.
JVMTI_ERROR_TYPE_MISMATCH The result type of the called method is not int, short, char, byte, or boolean.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are no frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Force Early Return - Long

jvmtiError
ForceEarlyReturnLong(jvmtiEnv* env,
            jthread thread,
            jlong value)
This function can be used to return from a method whose result type is long.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
83
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_force_early_return Can return early from a method, as described in the Force Early Return category.
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to return early. If thread is null, the current thread is used.
valuejlong The return value for the called frame.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_force_early_return. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Attempted to return early from a frame corresponding to a native method. The thread is a suspended virtual thread and the implementation was unable to force its current frame to return. Or the implementation is unable to provide this functionality on this frame.
JVMTI_ERROR_TYPE_MISMATCH The result type of the called method is not long.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are no frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Force Early Return - Float

jvmtiError
ForceEarlyReturnFloat(jvmtiEnv* env,
            jthread thread,
            jfloat value)
This function can be used to return from a method whose result type is float.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
84
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_force_early_return Can return early from a method, as described in the Force Early Return category.
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to return early. If thread is null, the current thread is used.
valuejfloat The return value for the called frame.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_force_early_return. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Attempted to return early from a frame corresponding to a native method. The thread is a suspended virtual thread and the implementation was unable to force its current frame to return. Or the implementation is unable to provide this functionality on this frame.
JVMTI_ERROR_TYPE_MISMATCH The result type of the called method is not float.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are no frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Force Early Return - Double

jvmtiError
ForceEarlyReturnDouble(jvmtiEnv* env,
            jthread thread,
            jdouble value)
This function can be used to return from a method whose result type is double.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
85
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_force_early_return Can return early from a method, as described in the Force Early Return category.
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to return early. If thread is null, the current thread is used.
valuejdouble The return value for the called frame.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_force_early_return. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Attempted to return early from a frame corresponding to a native method. The thread is a suspended virtual thread and the implementation was unable to force its current frame to return. Or the implementation is unable to provide this functionality on this frame.
JVMTI_ERROR_TYPE_MISMATCH The result type of the called method is not double.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are no frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Force Early Return - Void

jvmtiError
ForceEarlyReturnVoid(jvmtiEnv* env,
            jthread thread)
This function can be used to return from a method with no result type. That is, the called method must be declared void.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
86
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_force_early_return Can return early from a method, as described in the Force Early Return category.
Parameters
NameTypeDescription
threadjthread The thread whose current frame is to return early. If thread is null, the current thread is used.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_force_early_return. Use AddCapabilities.
JVMTI_ERROR_OPAQUE_FRAME Attempted to return early from a frame corresponding to a native method. The thread is a suspended virtual thread and the implementation was unable to force its current frame to return. Or the implementation is unable to provide this functionality on this frame.
JVMTI_ERROR_TYPE_MISMATCH The called method has a result type.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_NO_MORE_FRAMES There are no frames on the call stack.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).

Heap

Heap functions: Heap function types: Heap types: Heap flags and constants: These functions are used to analyze the heap. Functionality includes the ability to view the objects in the heap and to tag these objects.

Object Tags

A tag is a value associated with an object. Tags are explicitly set by the agent using the SetTag function or by callback functions such as jvmtiHeapIterationCallback.
Tags are local to the environment; that is, the tags of one environment are not visible in another.
Tags are jlong values which can be used simply to mark an object or to store a pointer to more detailed information. Objects which have not been tagged have a tag of zero. Setting a tag to zero makes the object untagged.

Heap Callback Functions

Heap functions which iterate through the heap and recursively follow object references use agent supplied callback functions to deliver the information.
These heap callback functions must adhere to the following restrictions -- These callbacks must not use JNI functions. These callbacks must not use JVM TI functions except callback safe functions which specifically allow such use (see the raw monitor, memory management, and environment local storage functions).
An implementation may invoke a callback on an internal thread or the thread which called the iteration function. Heap callbacks are single threaded -- no more than one callback will be invoked at a time.
The Heap Filter Flags can be used to prevent reporting based on the tag status of an object or its class. If no flags are set (the jint is zero), objects will not be filtered out.
Heap Filter Flags
ConstantValueDescription
JVMTI_HEAP_FILTER_TAGGED0x4 Filter out tagged objects. Objects which are tagged are not included.
JVMTI_HEAP_FILTER_UNTAGGED0x8 Filter out untagged objects. Objects which are not tagged are not included.
JVMTI_HEAP_FILTER_CLASS_TAGGED0x10 Filter out objects with tagged classes. Objects whose class is tagged are not included.
JVMTI_HEAP_FILTER_CLASS_UNTAGGED0x20 Filter out objects with untagged classes. Objects whose class is not tagged are not included.
The Heap Visit Control Flags are returned by the heap callbacks and can be used to abort the iteration. For the Heap Reference Callback, it can also be used to prune the graph of traversed references (JVMTI_VISIT_OBJECTS is not set).
Heap Visit Control Flags
ConstantValueDescription
JVMTI_VISIT_OBJECTS0x100 If we are visiting an object and if this callback was initiated by FollowReferences, traverse the references of this object. Otherwise ignored.
JVMTI_VISIT_ABORT0x8000 Abort the iteration. Ignore all other bits.
The Heap Reference Enumeration is provided by the Heap Reference Callback and Primitive Field Callback to describe the kind of reference being reported.
Heap Reference Enumeration (jvmtiHeapReferenceKind)
ConstantValueDescription
JVMTI_HEAP_REFERENCE_CLASS1 Reference from an object to its class.
JVMTI_HEAP_REFERENCE_FIELD2 Reference from an object to the value of one of its instance fields.
JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT3 Reference from an array to one of its elements.
JVMTI_HEAP_REFERENCE_CLASS_LOADER4 Reference from a class to its class loader.
JVMTI_HEAP_REFERENCE_SIGNERS5 Reference from a class to its signers array.
JVMTI_HEAP_REFERENCE_PROTECTION_DOMAIN6 Reference from a class to its protection domain.
JVMTI_HEAP_REFERENCE_INTERFACE7 Reference from a class to one of its interfaces. Note: interfaces are defined via a constant pool reference, so the referenced interfaces may also be reported with a JVMTI_HEAP_REFERENCE_CONSTANT_POOL reference kind.
JVMTI_HEAP_REFERENCE_STATIC_FIELD8 Reference from a class to the value of one of its static fields.
JVMTI_HEAP_REFERENCE_CONSTANT_POOL9 Reference from a class to a resolved entry in the constant pool.
JVMTI_HEAP_REFERENCE_SUPERCLASS10 Reference from a class to its superclass. A callback is not sent if the superclass is java.lang.Object. Note: loaded classes define superclasses via a constant pool reference, so the referenced superclass may also be reported with a JVMTI_HEAP_REFERENCE_CONSTANT_POOL reference kind.
JVMTI_HEAP_REFERENCE_JNI_GLOBAL21 Heap root reference: JNI global reference.
JVMTI_HEAP_REFERENCE_SYSTEM_CLASS22 Heap root reference: System class.
JVMTI_HEAP_REFERENCE_MONITOR23 Heap root reference: monitor.
JVMTI_HEAP_REFERENCE_STACK_LOCAL24 Local variable on a thread stack.
JVMTI_HEAP_REFERENCE_JNI_LOCAL25 JNI local reference.
JVMTI_HEAP_REFERENCE_THREAD26 Heap root reference: Thread.
JVMTI_HEAP_REFERENCE_OTHER27 Heap root reference: other heap root reference.
Definitions for the single character type descriptors of primitive types.
Primitive Type Enumeration (jvmtiPrimitiveType)
ConstantValueDescription
JVMTI_PRIMITIVE_TYPE_BOOLEAN90 'Z' - Java programming language boolean - JNI jboolean
JVMTI_PRIMITIVE_TYPE_BYTE66 'B' - Java programming language byte - JNI jbyte
JVMTI_PRIMITIVE_TYPE_CHAR67 'C' - Java programming language char - JNI jchar
JVMTI_PRIMITIVE_TYPE_SHORT83 'S' - Java programming language short - JNI jshort
JVMTI_PRIMITIVE_TYPE_INT73 'I' - Java programming language int - JNI jint
JVMTI_PRIMITIVE_TYPE_LONG74 'J' - Java programming language long - JNI jlong
JVMTI_PRIMITIVE_TYPE_FLOAT70 'F' - Java programming language float - JNI jfloat
JVMTI_PRIMITIVE_TYPE_DOUBLE68 'D' - Java programming language double - JNI jdouble

Reference information structure for Field references

Reference information returned for JVMTI_HEAP_REFERENCE_FIELD and JVMTI_HEAP_REFERENCE_STATIC_FIELD references. 
typedef struct {
    jint index;
} jvmtiHeapReferenceInfoField;
jvmtiHeapReferenceInfoField - Reference information structure for Field references
FieldTypeDescription
indexjint For JVMTI_HEAP_REFERENCE_FIELD, the referrer object is not a class or an interface. In this case, index is the index of the field in the class of the referrer object. This class is referred to below as C.
For JVMTI_HEAP_REFERENCE_STATIC_FIELD, the referrer object is a class (referred to below as C) or an interface (referred to below as I). In this case, index is the index of the field in that class or interface.
If the referrer object is not an interface, then the field indices are determined as follows:
  • make a list of all the fields in C and its superclasses, starting with all the fields in java.lang.Object and ending with all the fields in C.
  • Within this list, put the fields for a given class in the order returned by GetClassFields.
  • Assign the fields in this list indices n, n+1, ..., in order, where n is the count of the fields in all the interfaces implemented by C. Note that C implements all interfaces directly implemented by its superclasses; as well as all superinterfaces of these interfaces.
If the referrer object is an interface, then the field indices are determined as follows:
  • make a list of the fields directly declared in I.
  • Within this list, put the fields in the order returned by GetClassFields.
  • Assign the fields in this list indices n, n+1, ..., in order, where n is the count of the fields in all the superinterfaces of I.
All fields are included in this computation, regardless of field modifier (static, public, private, etc).
For example, given the following classes and interfaces: 
interface I0 {
    int p = 0;
}

interface I1 extends I0 {
    int x = 1;
}

interface I2 extends I0 {
    int y = 2;
}

class C1 implements I1 {
    public static int a = 3;
    private int b = 4;
}

class C2 extends C1 implements I2 {
    static int q = 5;
    final int r = 6;
}
Assume that GetClassFields called on C1 returns the fields of C1 in the order: a, b; and that the fields of C2 are returned in the order: q, r. An instance of class C1 will have the following field indices:
Field Index Description
a 2 The count of the fields in the interfaces implemented by C1 is two (n=2): p of I0 and x of I1.
b 3 the subsequent index.
The class C1 will have the same field indices.
An instance of class C2 will have the following field indices:
Field Index Description
a 3 The count of the fields in the interfaces implemented by C2 is three (n=3): p of I0, x of I1 and y of I2 (an interface of C2). Note that the field p of I0 is only included once.
b 4 the subsequent index to "a".
q 5 the subsequent index to "b".
r 6 the subsequent index to "q".
The class C2 will have the same field indices. Note that a field may have a different index depending on the object that is viewing it -- for example field "a" above. Note also: not all field indices may be visible from the callbacks, but all indices are shown for illustrative purposes.
The interface I1 will have the following field indices:
Field Index Description
x 1 The count of the fields in the superinterfaces of I1 is one (n=1): p of I0.

Reference information structure for Array references

Reference information returned for JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT references. 
typedef struct {
    jint index;
} jvmtiHeapReferenceInfoArray;
jvmtiHeapReferenceInfoArray - Reference information structure for Array references
FieldTypeDescription
indexjint The array index.

Reference information structure for Constant Pool references

Reference information returned for JVMTI_HEAP_REFERENCE_CONSTANT_POOL references. 
typedef struct {
    jint index;
} jvmtiHeapReferenceInfoConstantPool;
jvmtiHeapReferenceInfoConstantPool - Reference information structure for Constant Pool references
FieldTypeDescription
indexjint The index into the constant pool of the class. See the description in The Java™ Virtual Machine Specification, Chapter 4.4.

Reference information structure for Local Variable references

Reference information returned for JVMTI_HEAP_REFERENCE_STACK_LOCAL references. 
typedef struct {
    jlong thread_tag;
    jlong thread_id;
    jint depth;
    jmethodID method;
    jlocation location;
    jint slot;
} jvmtiHeapReferenceInfoStackLocal;
jvmtiHeapReferenceInfoStackLocal - Reference information structure for Local Variable references
FieldTypeDescription
thread_tagjlong The tag of the thread corresponding to this stack, zero if not tagged.
thread_idjlong The unique thread ID of the thread corresponding to this stack.
depthjint The depth of the frame.
methodjmethodID The method executing in this frame.
locationjlocation The currently executing location in this frame.
slotjint The slot number of the local variable.

Reference information structure for JNI local references

Reference information returned for JVMTI_HEAP_REFERENCE_JNI_LOCAL references. 
typedef struct {
    jlong thread_tag;
    jlong thread_id;
    jint depth;
    jmethodID method;
} jvmtiHeapReferenceInfoJniLocal;
jvmtiHeapReferenceInfoJniLocal - Reference information structure for JNI local references
FieldTypeDescription
thread_tagjlong The tag of the thread corresponding to this stack, zero if not tagged.
thread_idjlong The unique thread ID of the thread corresponding to this stack.
depthjint The depth of the frame.
methodjmethodID The method executing in this frame.

Reference information structure for Other references

Reference information returned for other references. 
typedef struct {
    jlong reserved1;
    jlong reserved2;
    jlong reserved3;
    jlong reserved4;
    jlong reserved5;
    jlong reserved6;
    jlong reserved7;
    jlong reserved8;
} jvmtiHeapReferenceInfoReserved;
jvmtiHeapReferenceInfoReserved - Reference information structure for Other references
FieldTypeDescription
reserved1jlong reserved for future use.
reserved2jlong reserved for future use.
reserved3jlong reserved for future use.
reserved4jlong reserved for future use.
reserved5jlong reserved for future use.
reserved6jlong reserved for future use.
reserved7jlong reserved for future use.
reserved8jlong reserved for future use.

Reference information structure

The information returned about referrers. Represented as a union of the various kinds of reference information. 
typedef union {
    jvmtiHeapReferenceInfoField field;
    jvmtiHeapReferenceInfoArray array;
    jvmtiHeapReferenceInfoConstantPool constant_pool;
    jvmtiHeapReferenceInfoStackLocal stack_local;
    jvmtiHeapReferenceInfoJniLocal jni_local;
    jvmtiHeapReferenceInfoReserved other;
} jvmtiHeapReferenceInfo;
jvmtiHeapReferenceInfo - Reference information structure
FieldTypeDescription
fieldjvmtiHeapReferenceInfoField The referrer information for JVMTI_HEAP_REFERENCE_FIELD and JVMTI_HEAP_REFERENCE_STATIC_FIELD references.
arrayjvmtiHeapReferenceInfoArray The referrer information for For JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT references.
constant_pooljvmtiHeapReferenceInfoConstantPool The referrer information for For JVMTI_HEAP_REFERENCE_CONSTANT_POOL references.
stack_localjvmtiHeapReferenceInfoStackLocal The referrer information for For JVMTI_HEAP_REFERENCE_STACK_LOCAL references.
jni_localjvmtiHeapReferenceInfoJniLocal The referrer information for For JVMTI_HEAP_REFERENCE_JNI_LOCAL references.
otherjvmtiHeapReferenceInfoReserved reserved for future use.

Heap callback function structure

typedef struct {
    jvmtiHeapIterationCallback heap_iteration_callback;
    jvmtiHeapReferenceCallback heap_reference_callback;
    jvmtiPrimitiveFieldCallback primitive_field_callback;
    jvmtiArrayPrimitiveValueCallback array_primitive_value_callback;
    jvmtiStringPrimitiveValueCallback string_primitive_value_callback;
    jvmtiReservedCallback reserved5;
    jvmtiReservedCallback reserved6;
    jvmtiReservedCallback reserved7;
    jvmtiReservedCallback reserved8;
    jvmtiReservedCallback reserved9;
    jvmtiReservedCallback reserved10;
    jvmtiReservedCallback reserved11;
    jvmtiReservedCallback reserved12;
    jvmtiReservedCallback reserved13;
    jvmtiReservedCallback reserved14;
    jvmtiReservedCallback reserved15;
} jvmtiHeapCallbacks;
jvmtiHeapCallbacks - Heap callback function structure
FieldTypeDescription
heap_iteration_callback jvmtiHeapIterationCallback The callback to be called to describe an object in the heap. Used by the IterateThroughHeap function, ignored by the FollowReferences function.
heap_reference_callback jvmtiHeapReferenceCallback The callback to be called to describe an object reference. Used by the FollowReferences function, ignored by the IterateThroughHeap function.
primitive_field_callback jvmtiPrimitiveFieldCallback The callback to be called to describe a primitive field.
array_primitive_value_callback jvmtiArrayPrimitiveValueCallback The callback to be called to describe an array of primitive values.
string_primitive_value_callback jvmtiStringPrimitiveValueCallback The callback to be called to describe a String value.
reserved5 jvmtiReservedCallback Reserved for future use..
reserved6 jvmtiReservedCallback Reserved for future use..
reserved7 jvmtiReservedCallback Reserved for future use..
reserved8 jvmtiReservedCallback Reserved for future use..
reserved9 jvmtiReservedCallback Reserved for future use..
reserved10 jvmtiReservedCallback Reserved for future use..
reserved11 jvmtiReservedCallback Reserved for future use..
reserved12 jvmtiReservedCallback Reserved for future use..
reserved13 jvmtiReservedCallback Reserved for future use..
reserved14 jvmtiReservedCallback Reserved for future use..
reserved15 jvmtiReservedCallback Reserved for future use..

Rationale: The heap dumping functionality (below) uses a callback for each object. While it would seem that a buffered approach would provide better throughput, tests do not show this to be the case--possibly due to locality of memory reference or array access overhead.

Heap Iteration Callback

typedef jint (JNICALL *jvmtiHeapIterationCallback)
    (jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     jint length,
     void* user_data);
Agent supplied callback function. Describes (but does not pass in) an object in the heap.
This function should return a bit vector of the desired visit control flags. This will determine if the entire iteration should be aborted (the JVMTI_VISIT_OBJECTS flag is ignored).
See the heap callback function restrictions.
Parameters
NameTypeDescription
class_tagjlong The tag of the class of object (zero if the class is not tagged). If the object represents a runtime class, the class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
sizejlong Size of the object (in bytes). See GetObjectSize.
tag_ptrjlong* The object tag value, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
lengthjint If this object is an array, the length of the array. Otherwise negative one (-1).
user_datavoid* The user supplied data that was passed into the iteration function.

Heap Reference Callback

typedef jint (JNICALL *jvmtiHeapReferenceCallback)
    (jvmtiHeapReferenceKind reference_kind,
     const jvmtiHeapReferenceInfo* reference_info,
     jlong class_tag,
     jlong referrer_class_tag,
     jlong size,
     jlong* tag_ptr,
     jlong* referrer_tag_ptr,
     jint length,
     void* user_data);
Agent supplied callback function. Describes a reference from an object or the VM (the referrer) to another object (the referree) or a heap root to a referree.
This function should return a bit vector of the desired visit control flags. This will determine if the objects referenced by the referree should be visited or if the entire iteration should be aborted.
See the heap callback function restrictions.
Parameters
NameTypeDescription
reference_kindjvmtiHeapReferenceKind The kind of reference.
reference_infoconst jvmtiHeapReferenceInfo * Details about the reference. Set when the reference_kind is JVMTI_HEAP_REFERENCE_FIELD, JVMTI_HEAP_REFERENCE_STATIC_FIELD, JVMTI_HEAP_REFERENCE_ARRAY_ELEMENT, JVMTI_HEAP_REFERENCE_CONSTANT_POOL, JVMTI_HEAP_REFERENCE_STACK_LOCAL, or JVMTI_HEAP_REFERENCE_JNI_LOCAL. Otherwise a null pointer.
class_tagjlong The tag of the class of referree object (zero if the class is not tagged). If the referree object represents a runtime class, the class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
referrer_class_tagjlong The tag of the class of the referrer object (zero if the class is not tagged or the referree is a heap root). If the referrer object represents a runtime class, the referrer_class_tag is the tag associated with the java.lang.Class (zero if java.lang.Class is not tagged).
sizejlong Size of the referree object (in bytes). See GetObjectSize.
tag_ptrjlong* Points to the referree object tag value, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
referrer_tag_ptrjlong* Points to the tag of the referrer object, or points to the zero if the referrer object is not tagged. Null if the referrer in not an object (that is, this callback is reporting a heap root). To set the tag value to be associated with the referrer object the agent sets the jlong pointed to by the parameter. If this callback is reporting a reference from an object to itself, referrer_tag_ptr == tag_ptr.
lengthjint If this object is an array, the length of the array. Otherwise negative one (-1).
user_datavoid* The user supplied data that was passed into the iteration function.

Primitive Field Callback

typedef jint (JNICALL *jvmtiPrimitiveFieldCallback)
    (jvmtiHeapReferenceKind kind,
     const jvmtiHeapReferenceInfo* info,
     jlong object_class_tag,
     jlong* object_tag_ptr,
     jvalue value,
     jvmtiPrimitiveType value_type,
     void* user_data);
Agent supplied callback function which describes a primitive field of an object (the object). A primitive field is a field whose type is a primitive type. This callback will describe a static field if the object is a class, and otherwise will describe an instance field.
This function should return a bit vector of the desired visit control flags. This will determine if the entire iteration should be aborted (the JVMTI_VISIT_OBJECTS flag is ignored).
See the heap callback function restrictions.
Parameters
NameTypeDescription
kindjvmtiHeapReferenceKind The kind of field -- instance or static (JVMTI_HEAP_REFERENCE_FIELD or JVMTI_HEAP_REFERENCE_STATIC_FIELD).
infoconst jvmtiHeapReferenceInfo * Which field (the field index).
object_class_tagjlong The tag of the class of the object (zero if the class is not tagged). If the object represents a runtime class, the object_class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
object_tag_ptrjlong* Points to the tag of the object, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
valuejvalue The value of the field.
value_typejvmtiPrimitiveType The type of the field.
user_datavoid* The user supplied data that was passed into the iteration function.

Array Primitive Value Callback

typedef jint (JNICALL *jvmtiArrayPrimitiveValueCallback)
    (jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     jint element_count,
     jvmtiPrimitiveType element_type,
     const void* elements,
     void* user_data);
Agent supplied callback function. Describes the values in an array of a primitive type.
This function should return a bit vector of the desired visit control flags. This will determine if the entire iteration should be aborted (the JVMTI_VISIT_OBJECTS flag is ignored).
See the heap callback function restrictions.
Parameters
NameTypeDescription
class_tagjlong The tag of the class of the array object (zero if the class is not tagged).
sizejlong Size of the array (in bytes). See GetObjectSize.
tag_ptrjlong* Points to the tag of the array object, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
element_countjint The length of the primitive array.
element_typejvmtiPrimitiveType The type of the elements of the array.
elementsconst void* The elements of the array in a packed array of element_count items of element_type size each.
user_datavoid* The user supplied data that was passed into the iteration function.

String Primitive Value Callback

typedef jint (JNICALL *jvmtiStringPrimitiveValueCallback)
    (jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     const jchar* value,
     jint value_length,
     void* user_data);
Agent supplied callback function. Describes the value of a java.lang.String.
This function should return a bit vector of the desired visit control flags. This will determine if the entire iteration should be aborted (the JVMTI_VISIT_OBJECTS flag is ignored).
See the heap callback function restrictions.
Parameters
NameTypeDescription
class_tagjlong The tag of the class of the String class (zero if the class is not tagged).
sizejlong Size of the string (in bytes). See GetObjectSize.
tag_ptrjlong* Points to the tag of the String object, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
valueconst jchar* The value of the String, encoded as a Unicode string.
value_lengthjint The length of the string. The length is equal to the number of 16-bit Unicode characters in the string.
user_datavoid* The user supplied data that was passed into the iteration function.

reserved for future use Callback

typedef jint (JNICALL *jvmtiReservedCallback)
    ();
Placeholder -- reserved for future use.
Parameters
None

Follow References

jvmtiError
FollowReferences(jvmtiEnv* env,
            jint heap_filter,
            jclass klass,
            jobject initial_object,
            const jvmtiHeapCallbacks* callbacks,
            const void* user_data)
This function initiates a traversal over the objects that are directly and indirectly reachable from the specified object or, if initial_object is not specified, all objects reachable from the heap roots. The heap root are the set of system classes, JNI globals, references from platform thread stacks, and other objects used as roots for the purposes of garbage collection.
This function operates by traversing the reference graph. Let A, B, ... represent objects. When a reference from A to B is traversed, when a reference from a heap root to B is traversed, or when B is specified as the initial_object, then B is said to be visited. A reference from A to B is not traversed until A is visited. References are reported in the same order that the references are traversed. Object references are reported by invoking the agent supplied callback function jvmtiHeapReferenceCallback. In a reference from A to B, A is known as the referrer and B as the referree. The callback is invoked exactly once for each reference from a referrer; this is true even if there are reference cycles or multiple paths to the referrer. There may be more than one reference between a referrer and a referree, each reference is reported. These references may be distinguished by examining the reference_kind and reference_info parameters of the jvmtiHeapReferenceCallback callback.
This function reports a Java programming language view of object references, not a virtual machine implementation view. The following object references are reported when they are non-null:
This function can also be used to examine primitive (non-object) values. The primitive value of an array or String is reported after the object has been visited; it is reported by invoking the agent supplied callback function jvmtiArrayPrimitiveValueCallback or jvmtiStringPrimitiveValueCallback. A primitive field is reported after the object with that field is visited; it is reported by invoking the agent supplied callback function jvmtiPrimitiveFieldCallback.
Whether a callback is provided or is null only determines whether the callback will be invoked, it does not influence which objects are visited nor does it influence whether other callbacks will be invoked. However, the visit control flags returned by jvmtiHeapReferenceCallback do determine if the objects referenced by the current object as visited. The heap filter flags and klass provided as parameters to this function do not control which objects are visited but they do control which objects and primitive values are reported by the callbacks. For example, if the only callback that was set is array_primitive_value_callback and klass is set to the array of bytes class, then only arrays of byte will be reported. The table below summarizes this:
Controls objects visited Controls objects reported Controls primitives reported
the Heap Visit Control Flags returned by jvmtiHeapReferenceCallback Yes Yes, since visits are controlled Yes, since visits are controlled
array_primitive_value_callback in callbacks set No Yes No
heap_filter No Yes Yes
klass No Yes Yes
During the execution of this function the state of the heap does not change: no objects are allocated, no objects are garbage collected, and the state of objects (including held values) does not change. As a result, threads executing Java programming language code, threads attempting to resume the execution of Java programming language code, and threads attempting to execute JNI functions are typically stalled.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
115
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
heap_filterjint This bit vector of heap filter flags. restricts the objects for which the callback function is called. This applies to both the object and primitive callbacks.
klass jclass Callbacks are only reported when the object is an instance of this class. Objects which are instances of a subclass of klass are not reported. If klass is an interface, no objects are reported. This applies to both the object and primitive callbacks.
If klass is null pointer, callbacks are not limited to instances of a particular class.
initial_object jobject The object to follow
If initial_object is null pointer, references are followed from the heap roots.
callbacksconst jvmtiHeapCallbacks * Structure defining the set of callback functions.
Agent passes in a pointer to jvmtiHeapCallbacks.
user_dataconst void * User supplied data to be passed to the callback.
Agent passes in a pointer. If user_data is null pointer, a null pointer is passed as the user supplied data.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_INVALID_CLASS klass is not a valid class.
JVMTI_ERROR_INVALID_OBJECT initial_object is not a valid object.
JVMTI_ERROR_NULL_POINTER callbacks is a null pointer .

Iterate Through Heap

jvmtiError
IterateThroughHeap(jvmtiEnv* env,
            jint heap_filter,
            jclass klass,
            const jvmtiHeapCallbacks* callbacks,
            const void* user_data)
Initiate an iteration over all objects in the heap. This includes both reachable and unreachable objects. Objects are visited in no particular order.
Heap objects are reported by invoking the agent supplied callback function jvmtiHeapIterationCallback. References between objects are not reported. If only reachable objects are desired, or if object reference information is needed, use FollowReferences.
This function can also be used to examine primitive (non-object) values. The primitive value of an array or String is reported after the object has been visited; it is reported by invoking the agent supplied callback function jvmtiArrayPrimitiveValueCallback or jvmtiStringPrimitiveValueCallback. A primitive field is reported after the object with that field is visited; it is reported by invoking the agent supplied callback function jvmtiPrimitiveFieldCallback.
Unless the iteration is aborted by the Heap Visit Control Flags returned by a callback, all objects in the heap are visited. Whether a callback is provided or is null only determines whether the callback will be invoked, it does not influence which objects are visited nor does it influence whether other callbacks will be invoked. The heap filter flags and klass provided as parameters to this function do not control which objects are visited but they do control which objects and primitive values are reported by the callbacks. For example, if the only callback that was set is array_primitive_value_callback and klass is set to the array of bytes class, then only arrays of byte will be reported. The table below summarizes this (contrast this with FollowReferences):
Controls objects visited Controls objects reported Controls primitives reported
the Heap Visit Control Flags returned by jvmtiHeapIterationCallback No
(unless they abort the iteration) 		No
(unless they abort the iteration) 		No
(unless they abort the iteration)
array_primitive_value_callback in callbacks set No Yes No
heap_filter No Yes Yes
klass No Yes Yes
During the execution of this function the state of the heap does not change: no objects are allocated, no objects are garbage collected, and the state of objects (including held values) does not change. As a result, threads executing Java programming language code, threads attempting to resume the execution of Java programming language code, and threads attempting to execute JNI functions are typically stalled.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
116
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
heap_filterjint This bit vector of heap filter flags. restricts the objects for which the callback function is called. This applies to both the object and primitive callbacks.
klass jclass Callbacks are only reported when the object is an instance of this class. Objects which are instances of a subclass of klass are not reported. If klass is an interface, no objects are reported. This applies to both the object and primitive callbacks.
If klass is null pointer, callbacks are not limited to instances of a particular class.
callbacksconst jvmtiHeapCallbacks * Structure defining the set callback functions.
Agent passes in a pointer to jvmtiHeapCallbacks.
user_dataconst void * User supplied data to be passed to the callback.
Agent passes in a pointer. If user_data is null pointer, a null pointer is passed as the user supplied data.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_INVALID_CLASS klass is not a valid class.
JVMTI_ERROR_NULL_POINTER callbacks is a null pointer .

Get Tag

jvmtiError
GetTag(jvmtiEnv* env,
            jobject object,
            jlong* tag_ptr)
Retrieve the tag associated with an object. The tag is a long value typically used to store a unique identifier or pointer to object information. The tag is set with SetTag. Objects for which no tags have been set return a tag value of zero.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
106
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
objectjobject The object whose tag is to be retrieved.
tag_ptrjlong* On return, the referenced long is set to the value of the tag.
Agent passes a pointer to a jlong. On return, the jlong has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_INVALID_OBJECT object is not an object.
JVMTI_ERROR_NULL_POINTER tag_ptr is a null pointer .

Set Tag

jvmtiError
SetTag(jvmtiEnv* env,
            jobject object,
            jlong tag)
Set the tag associated with an object. The tag is a long value typically used to store a unique identifier or pointer to object information. The tag is visible with GetTag.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
107
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
objectjobject The object whose tag is to be set.
tagjlong The new value of the tag.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_INVALID_OBJECT object is not an object.

Get Objects With Tags

jvmtiError
GetObjectsWithTags(jvmtiEnv* env,
            jint tag_count,
            const jlong* tags,
            jint* count_ptr,
            jobject** object_result_ptr,
            jlong** tag_result_ptr)
Return objects in the heap with the specified tags. The format is parallel arrays of objects and tags.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
114
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
tag_countjint Number of tags to scan for.
tagsconst jlong * Scan for objects with these tags. Zero is not permitted in this array.
Agent passes in an array of tag_count elements of jlong.
count_ptr jint * Return the number of objects with any of the tags in tags.
Agent passes a pointer to a jint. On return, the jint has been set.
object_result_ptr jobject ** Returns the array of objects with any of the tags in tags.
Agent passes a pointer to a jobject*. On return, the jobject* points to a newly allocated array of size *count_ptr. The array should be freed with Deallocate. If object_result_ptr is null pointer, this information is not returned. The objects returned by object_result_ptr are JNI local references and must be managed.
tag_result_ptr jlong ** For each object in object_result_ptr, return the tag at the corresponding index.
Agent passes a pointer to a jlong*. On return, the jlong* points to a newly allocated array of size *count_ptr. The array should be freed with Deallocate. If tag_result_ptr is null pointer, this information is not returned.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_ILLEGAL_ARGUMENT Zero is present in tags.
JVMTI_ERROR_ILLEGAL_ARGUMENT tag_count is less than 0.
JVMTI_ERROR_NULL_POINTER tags is a null pointer .
JVMTI_ERROR_NULL_POINTER count_ptr is a null pointer .

Force Garbage Collection

jvmtiError
ForceGarbageCollection(jvmtiEnv* env)
Force the VM to perform a garbage collection. The garbage collection is as complete as possible. This function does not cause finalizers to be run. This function does not return until the garbage collection is finished.
Although garbage collection is as complete as possible there is no guarantee that all ObjectFree events will have been sent by the time that this function returns. In particular, an object may be prevented from being freed because it is awaiting finalization.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
108
1.0
Capabilities
Required Functionality
Parameters
None
Errors
This function returns a universal error

Heap (1.0)

Heap (1.0) functions: Heap (1.0) function types: Heap (1.0) types: These functions and data types were introduced in the original JVM TI version 1.0. They are deprecated and will be changed to return an error in a future release. They were superseded in JVM TI version 1.2 (Java SE 6) by more powerful and flexible versions which:
Please use the current Heap functions.
Heap Object Filter Enumeration (jvmtiHeapObjectFilter)
ConstantValueDescription
JVMTI_HEAP_OBJECT_TAGGED1 Tagged objects only.
JVMTI_HEAP_OBJECT_UNTAGGED2 Untagged objects only.
JVMTI_HEAP_OBJECT_EITHER3 Either tagged or untagged objects.
Heap Root Kind Enumeration (jvmtiHeapRootKind)
ConstantValueDescription
JVMTI_HEAP_ROOT_JNI_GLOBAL1 JNI global reference.
JVMTI_HEAP_ROOT_SYSTEM_CLASS2 System class.
JVMTI_HEAP_ROOT_MONITOR3 Monitor.
JVMTI_HEAP_ROOT_STACK_LOCAL4 Stack local.
JVMTI_HEAP_ROOT_JNI_LOCAL5 JNI local reference.
JVMTI_HEAP_ROOT_THREAD6 Thread.
JVMTI_HEAP_ROOT_OTHER7 Other.
Object Reference Enumeration (jvmtiObjectReferenceKind)
ConstantValueDescription
JVMTI_REFERENCE_CLASS1 Reference from an object to its class.
JVMTI_REFERENCE_FIELD2 Reference from an object to the value of one of its instance fields. For references of this kind the referrer_index parameter to the jvmtiObjectReferenceCallback is the index of the the instance field. The index is based on the order of all the object's fields. This includes all fields of the directly declared static and instance fields in the class, and includes all fields (both public and private) fields declared in superclasses and superinterfaces. The index is thus calculated by summing the index of the field in the directly declared class (see GetClassFields), with the total number of fields (both public and private) declared in all superclasses and superinterfaces. The index starts at zero.
JVMTI_REFERENCE_ARRAY_ELEMENT3 Reference from an array to one of its elements. For references of this kind the referrer_index parameter to the jvmtiObjectReferenceCallback is the array index.
JVMTI_REFERENCE_CLASS_LOADER4 Reference from a class to its class loader.
JVMTI_REFERENCE_SIGNERS5 Reference from a class to its signers array.
JVMTI_REFERENCE_PROTECTION_DOMAIN6 Reference from a class to its protection domain.
JVMTI_REFERENCE_INTERFACE7 Reference from a class to one of its interfaces.
JVMTI_REFERENCE_STATIC_FIELD8 Reference from a class to the value of one of its static fields. For references of this kind the referrer_index parameter to the jvmtiObjectReferenceCallback is the index of the the static field. The index is based on the order of all the object's fields. This includes all fields of the directly declared static and instance fields in the class, and includes all fields (both public and private) fields declared in superclasses and superinterfaces. The index is thus calculated by summing the index of the field in the directly declared class (see GetClassFields), with the total number of fields (both public and private) declared in all superclasses and superinterfaces. The index starts at zero. Note: this definition differs from that in the JVM TI 1.0 Specification.

Rationale: No known implementations used the 1.0 definition.
JVMTI_REFERENCE_CONSTANT_POOL9 Reference from a class to a resolved entry in the constant pool. For references of this kind the referrer_index parameter to the jvmtiObjectReferenceCallback is the index into constant pool table of the class, starting at 1. See The Java™ Virtual Machine Specification, Chapter 4.4.
Iteration Control Enumeration (jvmtiIterationControl)
ConstantValueDescription
JVMTI_ITERATION_CONTINUE1 Continue the iteration. If this is a reference iteration, follow the references of this object.
JVMTI_ITERATION_IGNORE2 Continue the iteration. If this is a reference iteration, ignore the references of this object.
JVMTI_ITERATION_ABORT0 Abort the iteration.

Heap Object Callback

typedef jvmtiIterationControl (JNICALL *jvmtiHeapObjectCallback)
    (jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     void* user_data);
Agent supplied callback function. Describes (but does not pass in) an object in the heap.
Return value should be JVMTI_ITERATION_CONTINUE to continue iteration, or JVMTI_ITERATION_ABORT to stop iteration.
See the heap callback function restrictions.
Parameters
NameTypeDescription
class_tagjlong The tag of the class of object (zero if the class is not tagged). If the object represents a runtime class, the class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
sizejlong Size of the object (in bytes). See GetObjectSize.
tag_ptrjlong* The object tag value, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
user_datavoid* The user supplied data that was passed into the iteration function.

Heap Root Object Callback

typedef jvmtiIterationControl (JNICALL *jvmtiHeapRootCallback)
    (jvmtiHeapRootKind root_kind,
     jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     void* user_data);
Agent supplied callback function. Describes (but does not pass in) an object that is a root for the purposes of garbage collection.
Return value should be JVMTI_ITERATION_CONTINUE to continue iteration, JVMTI_ITERATION_IGNORE to continue iteration without pursuing references from referree object or JVMTI_ITERATION_ABORT to stop iteration.
See the heap callback function restrictions.
Parameters
NameTypeDescription
root_kindjvmtiHeapRootKind The kind of heap root.
class_tagjlong The tag of the class of object (zero if the class is not tagged). If the object represents a runtime class, the class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
sizejlong Size of the object (in bytes). See GetObjectSize.
tag_ptrjlong* The object tag value, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
user_datavoid* The user supplied data that was passed into the iteration function.

Stack Reference Object Callback

typedef jvmtiIterationControl (JNICALL *jvmtiStackReferenceCallback)
    (jvmtiHeapRootKind root_kind,
     jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     jlong thread_tag,
     jint depth,
     jmethodID method,
     jint slot,
     void* user_data);
Agent supplied callback function. Describes (but does not pass in) an object on the stack that is a root for the purposes of garbage collection.
Return value should be JVMTI_ITERATION_CONTINUE to continue iteration, JVMTI_ITERATION_IGNORE to continue iteration without pursuing references from referree object or JVMTI_ITERATION_ABORT to stop iteration.
See the heap callback function restrictions.
Parameters
NameTypeDescription
root_kindjvmtiHeapRootKind The kind of root (either JVMTI_HEAP_ROOT_STACK_LOCAL or JVMTI_HEAP_ROOT_JNI_LOCAL).
class_tagjlong The tag of the class of object (zero if the class is not tagged). If the object represents a runtime class, the class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
sizejlong Size of the object (in bytes). See GetObjectSize.
tag_ptrjlong* The object tag value, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
thread_tagjlong The tag of the thread corresponding to this stack, zero if not tagged.
depthjint The depth of the frame.
methodjmethodID The method executing in this frame.
slotjint The slot number.
user_datavoid* The user supplied data that was passed into the iteration function.

Object Reference Callback

typedef jvmtiIterationControl (JNICALL *jvmtiObjectReferenceCallback)
    (jvmtiObjectReferenceKind reference_kind,
     jlong class_tag,
     jlong size,
     jlong* tag_ptr,
     jlong referrer_tag,
     jint referrer_index,
     void* user_data);
Agent supplied callback function. Describes a reference from an object (the referrer) to another object (the referree).
Return value should be JVMTI_ITERATION_CONTINUE to continue iteration, JVMTI_ITERATION_IGNORE to continue iteration without pursuing references from referree object or JVMTI_ITERATION_ABORT to stop iteration.
See the heap callback function restrictions.
Parameters
NameTypeDescription
reference_kindjvmtiObjectReferenceKind The type of reference.
class_tagjlong The tag of the class of referree object (zero if the class is not tagged). If the referree object represents a runtime class, the class_tag is the tag associated with java.lang.Class (zero if java.lang.Class is not tagged).
sizejlong Size of the referree object (in bytes). See GetObjectSize.
tag_ptrjlong* The referree object tag value, or zero if the object is not tagged. To set the tag value to be associated with the object the agent sets the jlong pointed to by the parameter.
referrer_tagjlong The tag of the referrer object, or zero if the referrer object is not tagged.
referrer_indexjint For references of type JVMTI_REFERENCE_FIELD or JVMTI_REFERENCE_STATIC_FIELD the index of the field in the referrer object. The index is based on the order of all the object's fields - see JVMTI_REFERENCE_FIELD or JVMTI_REFERENCE_STATIC_FIELD for further description.
For references of type JVMTI_REFERENCE_ARRAY_ELEMENT the array index - see JVMTI_REFERENCE_ARRAY_ELEMENT for further description.
For references of type JVMTI_REFERENCE_CONSTANT_POOL the index into the constant pool of the class - see JVMTI_REFERENCE_CONSTANT_POOL for further description.
For references of other kinds the referrer_index is -1.
user_datavoid* The user supplied data that was passed into the iteration function.

Iterate Over Objects Reachable From Object

jvmtiError
IterateOverObjectsReachableFromObject(jvmtiEnv* env,
            jobject object,
            jvmtiObjectReferenceCallback object_reference_callback,
            const void* user_data)
This function iterates over all objects that are directly and indirectly reachable from the specified object. For each object A (known as the referrer) with a reference to object B the specified callback function is called to describe the object reference. The callback is called exactly once for each reference from a referrer; this is true even if there are reference cycles or multiple paths to the referrer. There may be more than one reference between a referrer and a referree, These may be distinguished by the jvmtiObjectReferenceCallback.reference_kind and jvmtiObjectReferenceCallback.referrer_index. The callback for an object will always occur after the callback for its referrer.
See FollowReferences for the object references which are reported.
During the execution of this function the state of the heap does not change: no objects are allocated, no objects are garbage collected, and the state of objects (including held values) does not change. As a result, threads executing Java programming language code, threads attempting to resume the execution of Java programming language code, and threads attempting to execute JNI functions are typically stalled.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
109
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
objectjobject The object
object_reference_callback jvmtiObjectReferenceCallback The callback to be called to describe each object reference.
user_dataconst void * User supplied data to be passed to the callback.
Agent passes in a pointer. If user_data is null pointer, a null pointer is passed as the user supplied data.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_INVALID_OBJECT object is not an object.
JVMTI_ERROR_NULL_POINTER object_reference_callback is a null pointer .

Iterate Over Reachable Objects

jvmtiError
IterateOverReachableObjects(jvmtiEnv* env,
            jvmtiHeapRootCallback heap_root_callback,
            jvmtiStackReferenceCallback stack_ref_callback,
            jvmtiObjectReferenceCallback object_ref_callback,
            const void* user_data)
This function iterates over the root objects and all objects that are directly and indirectly reachable from the root objects. The root objects comprise the set of system classes, JNI globals, references from platform thread stacks, and other objects used as roots for the purposes of garbage collection.
For each root the heap_root_callback or stack_ref_callback callback is called. An object can be a root object for more than one reason and in that case the appropriate callback is called for each reason.
For each object reference the object_ref_callback callback function is called to describe the object reference. The callback is called exactly once for each reference from a referrer; this is true even if there are reference cycles or multiple paths to the referrer. There may be more than one reference between a referrer and a referree, These may be distinguished by the jvmtiObjectReferenceCallback.reference_kind and jvmtiObjectReferenceCallback.referrer_index. The callback for an object will always occur after the callback for its referrer.
See FollowReferences for the object references which are reported.
Roots are always reported to the profiler before any object references are reported. In other words, the object_ref_callback callback will not be called until the appropriate callback has been called for all roots. If the object_ref_callback callback is specified as null then this function returns after reporting the root objects to the profiler.
During the execution of this function the state of the heap does not change: no objects are allocated, no objects are garbage collected, and the state of objects (including held values) does not change. As a result, threads executing Java programming language code, threads attempting to resume the execution of Java programming language code, and threads attempting to execute JNI functions are typically stalled.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
110
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
heap_root_callback jvmtiHeapRootCallback The callback function to be called for each heap root of type JVMTI_HEAP_ROOT_JNI_GLOBAL, JVMTI_HEAP_ROOT_SYSTEM_CLASS, JVMTI_HEAP_ROOT_MONITOR, JVMTI_HEAP_ROOT_THREAD, or JVMTI_HEAP_ROOT_OTHER.
If heap_root_callback is null pointer, do not report heap roots.
stack_ref_callback jvmtiStackReferenceCallback The callback function to be called for each heap root of JVMTI_HEAP_ROOT_STACK_LOCAL or JVMTI_HEAP_ROOT_JNI_LOCAL.
If stack_ref_callback is null pointer, do not report stack references.
object_ref_callback jvmtiObjectReferenceCallback The callback function to be called for each object reference.
If object_ref_callback is null pointer, do not follow references from the root objects.
user_dataconst void * User supplied data to be passed to the callback.
Agent passes in a pointer. If user_data is null pointer, a null pointer is passed as the user supplied data.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.

Iterate Over Heap

jvmtiError
IterateOverHeap(jvmtiEnv* env,
            jvmtiHeapObjectFilter object_filter,
            jvmtiHeapObjectCallback heap_object_callback,
            const void* user_data)
Iterate over all objects in the heap. This includes both reachable and unreachable objects.
The object_filter parameter indicates the objects for which the callback function is called. If this parameter is JVMTI_HEAP_OBJECT_TAGGED then the callback will only be called for every object that is tagged. If the parameter is JVMTI_HEAP_OBJECT_UNTAGGED then the callback will only be for objects that are not tagged. If the parameter is JVMTI_HEAP_OBJECT_EITHER then the callback will be called for every object in the heap, irrespective of whether it is tagged or not.
During the execution of this function the state of the heap does not change: no objects are allocated, no objects are garbage collected, and the state of objects (including held values) does not change. As a result, threads executing Java programming language code, threads attempting to resume the execution of Java programming language code, and threads attempting to execute JNI functions are typically stalled.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
111
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
object_filterjvmtiHeapObjectFilter Indicates the objects for which the callback function is called.
heap_object_callback jvmtiHeapObjectCallback The iterator function to be called for each object matching the object_filter.
user_dataconst void * User supplied data to be passed to the callback.
Agent passes in a pointer. If user_data is null pointer, a null pointer is passed as the user supplied data.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_ILLEGAL_ARGUMENT object_filter is not a jvmtiHeapObjectFilter.
JVMTI_ERROR_NULL_POINTER heap_object_callback is a null pointer .

Iterate Over Instances Of Class

jvmtiError
IterateOverInstancesOfClass(jvmtiEnv* env,
            jclass klass,
            jvmtiHeapObjectFilter object_filter,
            jvmtiHeapObjectCallback heap_object_callback,
            const void* user_data)
Iterate over all objects in the heap that are instances of the specified class. This includes direct instances of the specified class and instances of all subclasses of the specified class. This includes both reachable and unreachable objects.
The object_filter parameter indicates the objects for which the callback function is called. If this parameter is JVMTI_HEAP_OBJECT_TAGGED then the callback will only be called for every object that is tagged. If the parameter is JVMTI_HEAP_OBJECT_UNTAGGED then the callback will only be called for objects that are not tagged. If the parameter is JVMTI_HEAP_OBJECT_EITHER then the callback will be called for every object in the heap, irrespective of whether it is tagged or not.
During the execution of this function the state of the heap does not change: no objects are allocated, no objects are garbage collected, and the state of objects (including held values) does not change. As a result, threads executing Java programming language code, threads attempting to resume the execution of Java programming language code, and threads attempting to execute JNI functions are typically stalled.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
112
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_tag_objects Can set and get tags, as described in the Heap category.
Parameters
NameTypeDescription
klassjclass Iterate over objects of this class only.
object_filterjvmtiHeapObjectFilter Indicates the objects for which the callback function is called.
heap_object_callback jvmtiHeapObjectCallback The iterator function to be called for each klass instance matching the object_filter.
user_dataconst void * User supplied data to be passed to the callback.
Agent passes in a pointer. If user_data is null pointer, null pointeris passed as the user supplied data.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_tag_objects. Use AddCapabilities.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_ILLEGAL_ARGUMENT object_filter is not a jvmtiHeapObjectFilter.
JVMTI_ERROR_NULL_POINTER heap_object_callback is a null pointer .

Local Variable

Local Variable functions: These functions are used to retrieve or set the value of a local variable. The variable is identified by the depth of the frame containing its value and the variable's slot number within that frame. The mapping of variables to slot numbers can be obtained with the function GetLocalVariableTable.
The GetLocalXXX functions may be used to retrieve the value of a local variable contained in the frame of a virtual thread. The SetLocalXXX functions may be used to set the value of a local variable in the topmost frame of a virtual thread suspended at an event. An implementation may support setting locals in other cases.

Get Local Variable - Object

jvmtiError
GetLocalObject(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jobject* value_ptr)
This function can be used to retrieve the value of a local variable whose type is Object or a subclass of Object.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
21
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
value_ptrjobject* On return, points to the variable's value.
Agent passes a pointer to a jobject. On return, the jobject has been set. The object returned by value_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not Object or a subclass of Object.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER value_ptr is a null pointer .

Get Local Instance

jvmtiError
GetLocalInstance(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jobject* value_ptr)
This function can be used to retrieve the value of the local object variable at slot 0 (the "this" object) from non-static frames. This function can retrieve the "this" object from native method frames, whereas GetLocalObject() would return JVMTI_ERROR_OPAQUE_FRAME in those cases.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
155
1.2
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
value_ptrjobject* On return, points to the variable's value.
Agent passes a pointer to a jobject. On return, the jobject has been set. The object returned by value_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT If the specified frame is a static method frame.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER value_ptr is a null pointer .

Get Local Variable - Int

jvmtiError
GetLocalInt(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jint* value_ptr)
This function can be used to retrieve the value of a local variable whose type is int, short, char, byte, or boolean.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
22
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
value_ptrjint* On return, points to the variable's value.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not int, short, char, byte, or boolean.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER value_ptr is a null pointer .

Get Local Variable - Long

jvmtiError
GetLocalLong(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jlong* value_ptr)
This function can be used to retrieve the value of a local variable whose type is long.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
23
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
value_ptrjlong* On return, points to the variable's value.
Agent passes a pointer to a jlong. On return, the jlong has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not long.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER value_ptr is a null pointer .

Get Local Variable - Float

jvmtiError
GetLocalFloat(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jfloat* value_ptr)
This function can be used to retrieve the value of a local variable whose type is float.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
24
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
value_ptrjfloat* On return, points to the variable's value.
Agent passes a pointer to a jfloat. On return, the jfloat has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not float.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER value_ptr is a null pointer .

Get Local Variable - Double

jvmtiError
GetLocalDouble(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jdouble* value_ptr)
This function can be used to retrieve the value of a local variable whose type is long.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
25
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
value_ptrjdouble* On return, points to the variable's value.
Agent passes a pointer to a jdouble. On return, the jdouble has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not double.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_NULL_POINTER value_ptr is a null pointer .

Set Local Variable - Object

jvmtiError
SetLocalObject(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jobject value)
This function can be used to set the value of a local variable whose type is Object or a subclass of Object.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
26
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
valuejobject The new value for the variable.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not Object or a subclass of Object.
JVMTI_ERROR_TYPE_MISMATCH The supplied value is not compatible with the variable type.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation does not support setting the value of locals in the frame of the given depth. See Local Variables.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.
JVMTI_ERROR_INVALID_OBJECT value is not an object.

Set Local Variable - Int

jvmtiError
SetLocalInt(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jint value)
This function can be used to set the value of a local variable whose type is int, short, char, byte, or boolean.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
27
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
valuejint The new value for the variable.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not int, short, char, byte, or boolean.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation does not support setting the value of locals in the frame of the given depth. See Local Variables.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.

Set Local Variable - Long

jvmtiError
SetLocalLong(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jlong value)
This function can be used to set the value of a local variable whose type is long.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
28
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
valuejlong The new value for the variable.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not long.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation does not support setting the value of locals in the frame of the given depth. See Local Variables.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.

Set Local Variable - Float

jvmtiError
SetLocalFloat(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jfloat value)
This function can be used to set the value of a local variable whose type is float.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
29
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
valuejfloat The new value for the variable.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not float.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation does not support setting the value of locals in the frame of the given depth. See Local Variables.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.

Set Local Variable - Double

jvmtiError
SetLocalDouble(jvmtiEnv* env,
            jthread thread,
            jint depth,
            jint slot,
            jdouble value)
This function can be used to set the value of a local variable whose type is double.
The specified thread must be suspended or must be the current thread.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
30
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables
Parameters
NameTypeDescription
threadjthread The thread of the frame containing the variable's value. If thread is null, the current thread is used.
depthjint The depth of the frame containing the variable's value.
slotjint The variable's slot number.
valuejdouble The new value for the variable.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_INVALID_SLOT Invalid slot.
JVMTI_ERROR_TYPE_MISMATCH The variable type is not double.
JVMTI_ERROR_OPAQUE_FRAME Not a visible frame
JVMTI_ERROR_OPAQUE_FRAME The thread is a suspended virtual thread and the implementation does not support setting the value of locals in the frame of the given depth. See Local Variables.
JVMTI_ERROR_THREAD_NOT_SUSPENDED Thread was not suspended and was not the current thread.
JVMTI_ERROR_INVALID_THREAD thread is not a thread object.
JVMTI_ERROR_THREAD_NOT_ALIVE thread is not alive (has not been started or has terminated).
JVMTI_ERROR_ILLEGAL_ARGUMENT depth is less than zero.
JVMTI_ERROR_NO_MORE_FRAMES There are no stack frames at the specified depth.

Breakpoint

Breakpoint functions:

Set Breakpoint

jvmtiError
SetBreakpoint(jvmtiEnv* env,
            jmethodID method,
            jlocation location)
Set a breakpoint at the instruction indicated by method and location. An instruction can only have one breakpoint.
Whenever the designated instruction is about to be executed, a Breakpoint event is generated.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
38
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_breakpoint_events Can set and thus get Breakpoint events
Parameters
NameTypeDescription
methodjmethodID The method in which to set the breakpoint
locationjlocation the index of the instruction at which to set the breakpoint
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_breakpoint_events. Use AddCapabilities.
JVMTI_ERROR_DUPLICATE The designated bytecode already has a breakpoint.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_INVALID_LOCATION location is not a valid location.

Clear Breakpoint

jvmtiError
ClearBreakpoint(jvmtiEnv* env,
            jmethodID method,
            jlocation location)
Clear the breakpoint at the bytecode indicated by method and location.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
39
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_breakpoint_events Can set and thus get Breakpoint events
Parameters
NameTypeDescription
methodjmethodID The method in which to clear the breakpoint
locationjlocation the index of the instruction at which to clear the breakpoint
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_breakpoint_events. Use AddCapabilities.
JVMTI_ERROR_NOT_FOUND There's no breakpoint at the designated bytecode.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_INVALID_LOCATION location is not a valid location.

Watched Field

Watched Field functions:

Set Field Access Watch

jvmtiError
SetFieldAccessWatch(jvmtiEnv* env,
            jclass klass,
            jfieldID field)
Generate a FieldAccess event when the field specified by klass and field is about to be accessed. An event will be generated for each access of the field until it is canceled with ClearFieldAccessWatch. Field accesses from Java programming language code or from JNI code are watched, fields modified by other means are not watched. Note that JVM TI users should be aware that their own field accesses will trigger the watch. A field can only have one field access watch set. Modification of a field is not considered an access--use SetFieldModificationWatch to monitor modifications.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
41
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_field_access_events Can set watchpoints on field access - SetFieldAccessWatch
Parameters
NameTypeDescription
klassjclass The class containing the field to watch
fieldjfieldID The field to watch
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_field_access_events. Use AddCapabilities.
JVMTI_ERROR_DUPLICATE The designated field is already being watched for accesses.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.

Clear Field Access Watch

jvmtiError
ClearFieldAccessWatch(jvmtiEnv* env,
            jclass klass,
            jfieldID field)
Cancel a field access watch previously set by SetFieldAccessWatch, on the field specified by klass and field.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
42
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_field_access_events Can set watchpoints on field access - SetFieldAccessWatch
Parameters
NameTypeDescription
klassjclass The class containing the field to watch
fieldjfieldID The field to watch
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_field_access_events. Use AddCapabilities.
JVMTI_ERROR_NOT_FOUND The designated field is not being watched for accesses.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.

Set Field Modification Watch

jvmtiError
SetFieldModificationWatch(jvmtiEnv* env,
            jclass klass,
            jfieldID field)
Generate a FieldModification event when the field specified by klass and field is about to be modified. An event will be generated for each modification of the field until it is canceled with ClearFieldModificationWatch. Field modifications from Java programming language code or from JNI code are watched, fields modified by other means are not watched. Note that JVM TI users should be aware that their own field modifications will trigger the watch. A field can only have one field modification watch set.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
43
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_field_modification_events Can set watchpoints on field modification - SetFieldModificationWatch
Parameters
NameTypeDescription
klassjclass The class containing the field to watch
fieldjfieldID The field to watch
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_field_modification_events. Use AddCapabilities.
JVMTI_ERROR_DUPLICATE The designated field is already being watched for modifications.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.

Clear Field Modification Watch

jvmtiError
ClearFieldModificationWatch(jvmtiEnv* env,
            jclass klass,
            jfieldID field)
Cancel a field modification watch previously set by SetFieldModificationWatch, on the field specified by klass and field.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
44
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_generate_field_modification_events Can set watchpoints on field modification - SetFieldModificationWatch
Parameters
NameTypeDescription
klassjclass The class containing the field to watch
fieldjfieldID The field to watch
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_generate_field_modification_events. Use AddCapabilities.
JVMTI_ERROR_NOT_FOUND The designated field is not being watched for modifications.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.

Module

Module functions:

Get All Modules

jvmtiError
GetAllModules(jvmtiEnv* env,
            jint* module_count_ptr,
            jobject** modules_ptr)
Return an array of all modules loaded in the virtual machine. The array includes the unnamed module for each class loader. The number of modules in the array is returned via module_count_ptr, and the array itself via modules_ptr.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
3
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
module_count_ptrjint* On return, points to the number of returned modules.
Agent passes a pointer to a jint. On return, the jint has been set.
modules_ptrjobject** On return, points to an array of references, one for each module.
Agent passes a pointer to a jobject*. On return, the jobject* points to a newly allocated array of size *module_count_ptr. The array should be freed with Deallocate. The objects returned by modules_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER module_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER modules_ptr is a null pointer .

Get Named Module

jvmtiError
GetNamedModule(jvmtiEnv* env,
            jobject class_loader,
            const char* package_name,
            jobject* module_ptr)
Return the java.lang.Module object for a named module defined to a class loader that contains a given package. The module is returned via module_ptr.
If a named module is defined to the class loader and it contains the package then that named module is returned, otherwise null is returned.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
40
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
class_loader jobject A class loader. If the class_loader is not null or a subclass of java.lang.ClassLoader this function returns JVMTI_ERROR_ILLEGAL_ARGUMENT.
If class_loader is null pointer, the bootstrap loader is assumed.
package_nameconst char* The name of the package, encoded as a modified UTF-8 string. The package name is in internal form (JVMS 4.2.1); identifiers are separated by forward slashes rather than periods.
Agent passes in an array of char.
module_ptrjobject* On return, points to a java.lang.Module object or points to null.
Agent passes a pointer to a jobject. On return, the jobject has been set. The object returned by module_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_ILLEGAL_ARGUMENT If class loader is not null and is not a class loader object.
JVMTI_ERROR_NULL_POINTER package_name is a null pointer .
JVMTI_ERROR_NULL_POINTER module_ptr is a null pointer .

Add Module Reads

jvmtiError
AddModuleReads(jvmtiEnv* env,
            jobject module,
            jobject to_module)
Update a module to read another module. This function is a no-op when module is an unnamed module. This function facilitates the instrumentation of code in named modules where that instrumentation requires expanding the set of modules that a module reads.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
94
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
modulejobject The module to update.
to_modulejobject The additional module to read.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MODULE If module is not a module object.
JVMTI_ERROR_INVALID_MODULE If to_module is not a module object.
JVMTI_ERROR_UNMODIFIABLE_MODULE if the module cannot be modified. See IsModifiableModule.
JVMTI_ERROR_NULL_POINTER module is a null pointer .
JVMTI_ERROR_NULL_POINTER to_module is a null pointer .

Add Module Exports

jvmtiError
AddModuleExports(jvmtiEnv* env,
            jobject module,
            const char* pkg_name,
            jobject to_module)
Update a module to export a package to another module. This function is a no-op when module is an unnamed module or an open module. This function facilitates the instrumentation of code in named modules where that instrumentation requires expanding the set of packages that a module exports.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
95
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
modulejobject The module to update.
pkg_nameconst char* The exported package name.
Agent passes in an array of char.
to_modulejobject The module the package is exported to. If the to_module is not a subclass of java.lang.Module this function returns JVMTI_ERROR_INVALID_MODULE.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MODULE If module is not a module object.
JVMTI_ERROR_INVALID_MODULE If to_module is not a module object.
JVMTI_ERROR_ILLEGAL_ARGUMENT If the package pkg_name does not belong to the module.
JVMTI_ERROR_UNMODIFIABLE_MODULE if the module cannot be modified. See IsModifiableModule.
JVMTI_ERROR_NULL_POINTER module is a null pointer .
JVMTI_ERROR_NULL_POINTER pkg_name is a null pointer .
JVMTI_ERROR_NULL_POINTER to_module is a null pointer .

Add Module Opens

jvmtiError
AddModuleOpens(jvmtiEnv* env,
            jobject module,
            const char* pkg_name,
            jobject to_module)
Update a module to open a package to another module. This function is a no-op when module is an unnamed module or an open module. This function facilitates the instrumentation of code in modules where that instrumentation requires expanding the set of packages that a module opens to other modules.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
96
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
modulejobject The module to update.
pkg_nameconst char* The package name of the package to open.
Agent passes in an array of char.
to_modulejobject The module with the package to open. If the to_module is not a subclass of java.lang.Module this function returns JVMTI_ERROR_INVALID_MODULE.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MODULE If module is not a module object.
JVMTI_ERROR_INVALID_MODULE If to_module is not a module object.
JVMTI_ERROR_ILLEGAL_ARGUMENT If the package pkg_name does not belong to the module.
JVMTI_ERROR_UNMODIFIABLE_MODULE if the module cannot be modified. See IsModifiableModule.
JVMTI_ERROR_NULL_POINTER module is a null pointer .
JVMTI_ERROR_NULL_POINTER pkg_name is a null pointer .
JVMTI_ERROR_NULL_POINTER to_module is a null pointer .

Add Module Uses

jvmtiError
AddModuleUses(jvmtiEnv* env,
            jobject module,
            jclass service)
Updates a module to add a service to the set of services that a module uses. This function is a no-op when the module is an unnamed module. This function facilitates the instrumentation of code in named modules where that instrumentation requires expanding the set of services that a module is using.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
97
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
modulejobject The module to update.
servicejclass The service to use.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MODULE If module is not a module object.
JVMTI_ERROR_INVALID_CLASS If service is not a class object.
JVMTI_ERROR_UNMODIFIABLE_MODULE if the module cannot be modified. See IsModifiableModule.
JVMTI_ERROR_NULL_POINTER module is a null pointer .
JVMTI_ERROR_NULL_POINTER service is a null pointer .

Add Module Provides

jvmtiError
AddModuleProvides(jvmtiEnv* env,
            jobject module,
            jclass service,
            jclass impl_class)
Updates a module to add a service to the set of services that a module provides. This function is a no-op when the module is an unnamed module. This function facilitates the instrumentation of code in named modules where that instrumentation requires changes to the services that are provided.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
98
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
modulejobject The module to update.
servicejclass The service to provide.
impl_classjclass The implementation class for the provided service.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MODULE If module is not a module object.
JVMTI_ERROR_INVALID_CLASS If service is not a class object.
JVMTI_ERROR_INVALID_CLASS If impl_class is not a class object.
JVMTI_ERROR_UNMODIFIABLE_MODULE if the module cannot be modified. See IsModifiableModule.
JVMTI_ERROR_NULL_POINTER module is a null pointer .
JVMTI_ERROR_NULL_POINTER service is a null pointer .
JVMTI_ERROR_NULL_POINTER impl_class is a null pointer .

Is Modifiable Module

jvmtiError
IsModifiableModule(jvmtiEnv* env,
            jobject module,
            jboolean* is_modifiable_module_ptr)
Determines whether a module is modifiable. If a module is modifiable then this module can be updated with AddModuleReads, AddModuleExports, AddModuleOpens, AddModuleUses, and AddModuleProvides. If a module is not modifiable then the module can not be updated with these functions. The result of this function is always JNI_TRUE when called to determine if an unnamed module is modifiable.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
99
9
Capabilities
Required Functionality
Parameters
NameTypeDescription
modulejobject The module to query.
is_modifiable_module_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MODULE If module is not a module object.
JVMTI_ERROR_NULL_POINTER module is a null pointer .
JVMTI_ERROR_NULL_POINTER is_modifiable_module_ptr is a null pointer .

Class

Class functions: Class types: Class flags and constants:

Get Loaded Classes

jvmtiError
GetLoadedClasses(jvmtiEnv* env,
            jint* class_count_ptr,
            jclass** classes_ptr)
Return an array of all classes loaded in the virtual machine. The number of classes in the array is returned via class_count_ptr, and the array itself via classes_ptr.
A class or interface creation can be triggered by one of the following:
An array class is created directly by the Java virtual machine. The creation can be triggered by using class loaders or by invoking methods in certain Java SE Platform APIs such as reflection.
The returned list includes all classes and interfaces, including hidden classes or interfaces, and also array classes of all types (including arrays of primitive types). Primitive classes (for example, java.lang.Integer.TYPE) are not included in the returned list.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
78
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
class_count_ptrjint* On return, points to the number of classes.
Agent passes a pointer to a jint. On return, the jint has been set.
classes_ptrjclass** On return, points to an array of references, one for each class.
Agent passes a pointer to a jclass*. On return, the jclass* points to a newly allocated array of size *class_count_ptr. The array should be freed with Deallocate. The objects returned by classes_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER class_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER classes_ptr is a null pointer .

Get Classloader Classes

jvmtiError
GetClassLoaderClasses(jvmtiEnv* env,
            jobject initiating_loader,
            jint* class_count_ptr,
            jclass** classes_ptr)
Returns an array of all classes which this class loader can find by name via ClassLoader::loadClass, Class::forName and bytecode linkage. That is, all classes for which initiating_loader has been recorded as an initiating loader. Each class in the returned array was created by this class loader, either by defining it directly or by delegation to another class loader. See The Java™ Virtual Machine Specification, Chapter 5.3.
The returned list does not include hidden classes or interfaces or array classes whose element type is a hidden class or interface as they cannot be discovered by any class loader.
The number of classes in the array is returned via class_count_ptr, and the array itself via classes_ptr.
See Lookup::defineHiddenClass.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
79
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
initiating_loader jobject An initiating class loader.
If initiating_loader is null pointer, the classes initiated by the bootstrap loader will be returned.
class_count_ptrjint* On return, points to the number of classes.
Agent passes a pointer to a jint. On return, the jint has been set.
classes_ptrjclass** On return, points to an array of references, one for each class.
Agent passes a pointer to a jclass*. On return, the jclass* points to a newly allocated array of size *class_count_ptr. The array should be freed with Deallocate. The objects returned by classes_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER class_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER classes_ptr is a null pointer .

Get Class Signature

jvmtiError
GetClassSignature(jvmtiEnv* env,
            jclass klass,
            char** signature_ptr,
            char** generic_ptr)
Return the name and the generic signature of the class indicated by klass.
If the class is a class or interface, then:
If the class indicated by klass represents an array class, then the returned name is a string consisting of one or more "[" characters representing the depth of the array nesting, followed by the class signature of the element type. For example the class signature of java.lang.String[] is "[Ljava/lang/String;" and that of int[] is "[I".
If the class indicated by klass represents primitive type or void, then the returned name is the type signature character of the corresponding primitive type. For example, java.lang.Integer.TYPE is "I".
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
48
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
signature_ptr char ** On return, points to the JNI type signature of the class, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If signature_ptr is null pointer, the signature is not returned.
generic_ptr char ** On return, points to the generic signature of the class, encoded as a modified UTF-8 string. If there is no generic signature attribute for the class, then, on return, points to null.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If generic_ptr is null pointer, the generic signature is not returned.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.

Get Class Status

jvmtiError
GetClassStatus(jvmtiEnv* env,
            jclass klass,
            jint* status_ptr)
Get the status of the class. Zero or more of the following bits can be set.
Class Status Flags
ConstantValueDescription
JVMTI_CLASS_STATUS_VERIFIED1 Class bytecodes have been verified
JVMTI_CLASS_STATUS_PREPARED2 Class preparation is complete
JVMTI_CLASS_STATUS_INITIALIZED4 Class initialization is complete. Static initializer has been run.
JVMTI_CLASS_STATUS_ERROR8 Error during initialization makes class unusable
JVMTI_CLASS_STATUS_ARRAY16 Class is an array. If set, all other bits are zero.
JVMTI_CLASS_STATUS_PRIMITIVE32 Class is a primitive class (for example, java.lang.Integer.TYPE). If set, all other bits are zero.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
49
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
status_ptrjint* On return, points to the current state of this class as one or more of the class status flags.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER status_ptr is a null pointer .

Get Source File Name

jvmtiError
GetSourceFileName(jvmtiEnv* env,
            jclass klass,
            char** source_name_ptr)
For the class indicated by klass, return the source file name via source_name_ptr. The returned string is a file name only and never contains a directory name.
For primitive classes (for example, java.lang.Integer.TYPE) and for arrays this function returns JVMTI_ERROR_ABSENT_INFORMATION.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
50
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_source_file_name Can get the source file name of a class
Parameters
NameTypeDescription
klassjclass The class to query.
source_name_ptrchar** On return, points to the class's source file name, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_source_file_name. Use AddCapabilities.
JVMTI_ERROR_ABSENT_INFORMATION Class information does not include a source file name. This includes cases where the class is an array class or primitive class.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER source_name_ptr is a null pointer .

Get Class Modifiers

jvmtiError
GetClassModifiers(jvmtiEnv* env,
            jclass klass,
            jint* modifiers_ptr)
For the class indicated by klass, return the access flags via modifiers_ptr. Access flags are defined in The Java™ Virtual Machine Specification, Chapter 4.
If the class is an array class, then its public, private, and protected modifiers are the same as those of its component type. For arrays of primitives, this component type is represented by one of the primitive classes (for example, java.lang.Integer.TYPE).
If the class is a primitive class, its public modifier is always true, and its protected and private modifiers are always false.
If the class is an array class or a primitive class then its final modifier is always true and its interface modifier is always false. The values of its other modifiers are not determined by this specification.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
51
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
modifiers_ptrjint* On return, points to the current access flags of this class.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER modifiers_ptr is a null pointer .

Get Class Methods

jvmtiError
GetClassMethods(jvmtiEnv* env,
            jclass klass,
            jint* method_count_ptr,
            jmethodID** methods_ptr)
For the class indicated by klass, return a count of methods via method_count_ptr and a list of method IDs via methods_ptr. The method list contains constructors and static initializers as well as true methods. Only directly declared methods are returned (not inherited methods). An empty method list is returned for array classes and primitive classes (for example, java.lang.Integer.TYPE).
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
52
1.0
Capabilities
Required Functionality
Optional Features
CapabilityEffect
can_maintain_original_method_order Can return methods in the order they occur in the class file
Parameters
NameTypeDescription
klassjclass The class to query.
method_count_ptrjint* On return, points to the number of methods declared in this class.
Agent passes a pointer to a jint. On return, the jint has been set.
methods_ptrjmethodID** On return, points to the method ID array.
Agent passes a pointer to a jmethodID*. On return, the jmethodID* points to a newly allocated array of size *method_count_ptr. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_CLASS_NOT_PREPARED klass is not prepared.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER method_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER methods_ptr is a null pointer .

Get Class Fields

jvmtiError
GetClassFields(jvmtiEnv* env,
            jclass klass,
            jint* field_count_ptr,
            jfieldID** fields_ptr)
For the class indicated by klass, return a count of fields via field_count_ptr and a list of field IDs via fields_ptr. Only directly declared fields are returned (not inherited fields). Fields are returned in the order they occur in the class file. An empty field list is returned for array classes and primitive classes (for example, java.lang.Integer.TYPE). Use JNI to determine the length of an array.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
53
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
field_count_ptrjint* On return, points to the number of fields declared in this class.
Agent passes a pointer to a jint. On return, the jint has been set.
fields_ptrjfieldID** On return, points to the field ID array.
Agent passes a pointer to a jfieldID*. On return, the jfieldID* points to a newly allocated array of size *field_count_ptr. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_CLASS_NOT_PREPARED klass is not prepared.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER field_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER fields_ptr is a null pointer .

Get Implemented Interfaces

jvmtiError
GetImplementedInterfaces(jvmtiEnv* env,
            jclass klass,
            jint* interface_count_ptr,
            jclass** interfaces_ptr)
Return the direct super-interfaces of this class. For a class, this function returns the interfaces declared in its implements clause. For an interface, this function returns the interfaces declared in its extends clause. An empty interface list is returned for array classes and primitive classes (for example, java.lang.Integer.TYPE).
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
54
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
interface_count_ptrjint* On return, points to the number of interfaces.
Agent passes a pointer to a jint. On return, the jint has been set.
interfaces_ptrjclass** On return, points to the interface array.
Agent passes a pointer to a jclass*. On return, the jclass* points to a newly allocated array of size *interface_count_ptr. The array should be freed with Deallocate. The objects returned by interfaces_ptr are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_CLASS_NOT_PREPARED klass is not prepared.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER interface_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER interfaces_ptr is a null pointer .

Get Class Version Numbers

jvmtiError
GetClassVersionNumbers(jvmtiEnv* env,
            jclass klass,
            jint* minor_version_ptr,
            jint* major_version_ptr)
For the class indicated by klass, return the minor and major version numbers, as defined in The Java™ Virtual Machine Specification, Chapter 4.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
145
1.1
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
minor_version_ptrjint* On return, points to the value of the minor_version item of the Class File Format. Note: to be consistent with the Class File Format, the minor version number is the first parameter.
Agent passes a pointer to a jint. On return, the jint has been set.
major_version_ptrjint* On return, points to the value of the major_version item of the Class File Format.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_ABSENT_INFORMATION The class is a primitive or array class.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER minor_version_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER major_version_ptr is a null pointer .

Get Constant Pool

jvmtiError
GetConstantPool(jvmtiEnv* env,
            jclass klass,
            jint* constant_pool_count_ptr,
            jint* constant_pool_byte_count_ptr,
            unsigned char** constant_pool_bytes_ptr)
For the class indicated by klass, return the raw bytes of the constant pool in the format of the constant_pool item of The Java™ Virtual Machine Specification, Chapter 4. The format of the constant pool may differ between versions of the Class File Format, so, the minor and major class version numbers should be checked for compatibility.
The returned constant pool might not have the same layout or contents as the constant pool in the defining class file. The constant pool returned by GetConstantPool() may have more or fewer entries than the defining constant pool. Entries may be in a different order. The constant pool returned by GetConstantPool() will match the constant pool used by GetBytecodes(). That is, the bytecodes returned by GetBytecodes() will have constant pool indices which refer to constant pool entries returned by GetConstantPool(). Note that since RetransformClasses and RedefineClasses can change the constant pool, the constant pool returned by this function can change accordingly. Thus, the correspondence between GetConstantPool() and GetBytecodes() does not hold if there is an intervening class retransformation or redefinition. The value of a constant pool entry used by a given bytecode will match that of the defining class file (even if the indices don't match). Constant pool entries which are not used directly or indirectly by bytecodes (for example, UTF-8 strings associated with annotations) are not required to exist in the returned constant pool.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
146
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_constant_pool Can get the constant pool of a class - GetConstantPool
Parameters
NameTypeDescription
klassjclass The class to query.
constant_pool_count_ptrjint* On return, points to the number of entries in the constant pool table plus one. This corresponds to the constant_pool_count item of the Class File Format.
Agent passes a pointer to a jint. On return, the jint has been set.
constant_pool_byte_count_ptrjint* On return, points to the number of bytes in the returned raw constant pool.
Agent passes a pointer to a jint. On return, the jint has been set.
constant_pool_bytes_ptrunsigned char** On return, points to the raw constant pool, that is the bytes defined by the constant_pool item of the Class File Format
Agent passes a pointer to a unsigned char*. On return, the unsigned char* points to a newly allocated array of size *constant_pool_byte_count_ptr. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_constant_pool. Use AddCapabilities.
JVMTI_ERROR_ABSENT_INFORMATION The class is a primitive or array class.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER constant_pool_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER constant_pool_byte_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER constant_pool_bytes_ptr is a null pointer .

Is Interface

jvmtiError
IsInterface(jvmtiEnv* env,
            jclass klass,
            jboolean* is_interface_ptr)
Determines whether a class object reference represents an interface. The jboolean result is JNI_TRUE if the "class" is actually an interface, JNI_FALSE otherwise.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
55
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
is_interface_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER is_interface_ptr is a null pointer .

Is Array Class

jvmtiError
IsArrayClass(jvmtiEnv* env,
            jclass klass,
            jboolean* is_array_class_ptr)
Determines whether a class object reference represents an array. The jboolean result is JNI_TRUE if the class is an array, JNI_FALSE otherwise.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
56
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
is_array_class_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER is_array_class_ptr is a null pointer .

Is Modifiable Class

jvmtiError
IsModifiableClass(jvmtiEnv* env,
            jclass klass,
            jboolean* is_modifiable_class_ptr)
Determines whether a class is modifiable. If a class is modifiable (is_modifiable_class_ptr returns JNI_TRUE) the class can be redefined with RedefineClasses (assuming the agent possesses the can_redefine_classes capability) or retransformed with RetransformClasses (assuming the agent possesses the can_retransform_classes capability). If a class is not modifiable (is_modifiable_class_ptr returns JNI_FALSE) the class can be neither redefined nor retransformed.
Primitive classes (for example, java.lang.Integer.TYPE), array classes, and some implementation defined classes are never modifiable.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
45
1.1
Capabilities
Required Functionality
Optional Features
CapabilityEffect
can_redefine_any_class If possessed then all classes (except primitive, array, and some implementation defined classes) are modifiable with RedefineClasses.
can_retransform_any_class If possessed then all classes (except primitive, array, and some implementation defined classes) are modifiable with RetransformClasses.
can_redefine_classes No effect on the result of the function. But must additionally be possessed to modify the class with RedefineClasses.
can_retransform_classes No effect on the result of the function. But must additionally be possessed to modify the class with RetransformClasses.
Parameters
NameTypeDescription
klassjclass The class to query.
is_modifiable_class_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER is_modifiable_class_ptr is a null pointer .

Get Class Loader

jvmtiError
GetClassLoader(jvmtiEnv* env,
            jclass klass,
            jobject* classloader_ptr)
For the class indicated by klass, return via classloader_ptr a reference to the class loader for the class.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
57
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
classloader_ptrjobject* On return, points to the class loader that loaded this class. If the class was not created by a class loader or if the class loader is the bootstrap class loader, points to null.
Agent passes a pointer to a jobject. On return, the jobject has been set. The object returned by classloader_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER classloader_ptr is a null pointer .

Get Source Debug Extension

jvmtiError
GetSourceDebugExtension(jvmtiEnv* env,
            jclass klass,
            char** source_debug_extension_ptr)
For the class indicated by klass, return the debug extension via source_debug_extension_ptr. The returned string contains exactly the debug extension information present in the class file of klass.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
90
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_source_debug_extension Can get the source debug extension of a class
Parameters
NameTypeDescription
klassjclass The class to query.
source_debug_extension_ptrchar** On return, points to the class's debug extension, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_source_debug_extension. Use AddCapabilities.
JVMTI_ERROR_ABSENT_INFORMATION Class information does not include a debug extension.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_NULL_POINTER source_debug_extension_ptr is a null pointer .

Retransform Classes

jvmtiError
RetransformClasses(jvmtiEnv* env,
            jint class_count,
            const jclass* classes)
This function facilitates the bytecode instrumentation of already loaded classes. To replace the class definition without reference to the existing bytecodes, as one might do when recompiling from source for fix-and-continue debugging, RedefineClasses function should be used instead.
When classes are initially loaded or when they are redefined, the initial class file bytes can be transformed with the ClassFileLoadHook event. This function reruns the transformation process (whether or not a transformation has previously occurred). This retransformation follows these steps: See the ClassFileLoadHook event for more details.
The initial class file bytes represent the bytes passed to ClassLoader.defineClass or RedefineClasses (before any transformations were applied), however they may not exactly match them. The constant pool may differ in ways described in GetConstantPool. Constant pool indices in the bytecodes of methods will correspond. Some attributes may not be present. Where order is not meaningful, for example the order of methods, order may not be preserved.
Retransformation can cause new versions of methods to be installed. Old method versions may become obsolete The new method version will be used on new invokes. If a method has active stack frames, those active frames continue to run the bytecodes of the original method version.
This function does not cause any initialization except that which would occur under the customary JVM semantics. In other words, retransforming a class does not cause its initializers to be run. The values of static fields will remain as they were prior to the call.
Threads need not be suspended.
All breakpoints in the class are cleared.
All attributes are updated.
Instances of the retransformed class are not affected -- fields retain their previous values. Tags on the instances are also unaffected.
In response to this call, no events other than the ClassFileLoadHook event will be sent.
The retransformation may change method bodies, the constant pool and attributes (unless explicitly prohibited). The retransformation must not add, remove or rename fields or methods, change the signatures of methods, change modifiers, or change inheritance. The retransformation must not change the NestHost, NestMembers, Record, or PermittedSubclasses attributes. These restrictions may be lifted in future versions. See the error return description below for information on error codes returned if an unsupported retransformation is attempted. The class file bytes are not verified or installed until they have passed through the chain of ClassFileLoadHook events, thus the returned error code reflects the result of the transformations. If any error code is returned other than JVMTI_ERROR_NONE, none of the classes to be retransformed will have a new definition installed. When this function returns (with the error code of JVMTI_ERROR_NONE) all of the classes to be retransformed will have their new definitions installed.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
152
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_retransform_classes Can retransform classes with RetransformClasses. In addition to the restrictions imposed by the specific implementation on this capability (see the Capability section), this capability must be set before the ClassFileLoadHook event is enabled for the first time in this environment. An environment that possesses this capability at the time that ClassFileLoadHook is enabled for the first time is said to be retransformation capable. An environment that does not possess this capability at the time that ClassFileLoadHook is enabled for the first time is said to be retransformation incapable.
Optional Features
can_retransform_any_class RetransformClasses can be called on any modifiable class. See IsModifiableClass. (can_retransform_classes must also be set)
Parameters
NameTypeDescription
class_countjint The number of classes to be retransformed.
classesconst jclass* The array of classes to be retransformed.
Agent passes in an array of class_count elements of jclass.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_retransform_classes. Use AddCapabilities.
JVMTI_ERROR_UNMODIFIABLE_CLASS One of the classes cannot be modified. See IsModifiableClass.
JVMTI_ERROR_INVALID_CLASS One of the classes is not a valid class.
JVMTI_ERROR_UNSUPPORTED_VERSION A retransformed class file has a version number not supported by this VM.
JVMTI_ERROR_INVALID_CLASS_FORMAT A retransformed class file is malformed (The VM would return a ClassFormatError).
JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION The retransformed class file definitions would lead to a circular definition (the VM would return a ClassCircularityError).
JVMTI_ERROR_FAILS_VERIFICATION The retransformed class file bytes fail verification.
JVMTI_ERROR_NAMES_DONT_MATCH The class name defined in a retransformed class file is different from the name in the old class object.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED A retransformed class file would require adding a method.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED A retransformed class file changes a field.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED A direct superclass is different for a retransformed class file, or the set of directly implemented interfaces is different.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED A retransformed class file does not declare a method declared in the old class version.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED A retransformed class file has unsupported differences in class attributes.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED A retransformed class file has different class modifiers.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED A method in the retransformed class file has different modifiers than its counterpart in the old class version.
JVMTI_ERROR_ILLEGAL_ARGUMENT class_count is less than 0.
JVMTI_ERROR_NULL_POINTER classes is a null pointer .

Redefine Classes

typedef struct {
    jclass klass;
    jint class_byte_count;
    const unsigned char* class_bytes;
} jvmtiClassDefinition;
jvmtiError
RedefineClasses(jvmtiEnv* env,
            jint class_count,
            const jvmtiClassDefinition* class_definitions)
All classes given are redefined according to the definitions supplied. This function is used to replace the definition of a class with a new definition, as might be needed in fix-and-continue debugging. Where the existing class file bytes are to be transformed, for example in bytecode instrumentation, RetransformClasses should be used.
Redefinition can cause new versions of methods to be installed. Old method versions may become obsolete The new method version will be used on new invokes. If a method has active stack frames, those active frames continue to run the bytecodes of the original method version. If resetting of stack frames is desired, use PopFrame to pop frames with obsolete method versions.
This function does not cause any initialization except that which would occur under the customary JVM semantics. In other words, redefining a class does not cause its initializers to be run. The values of static fields will remain as they were prior to the call.
Threads need not be suspended.
All breakpoints in the class are cleared.
All attributes are updated.
Instances of the redefined class are not affected -- fields retain their previous values. Tags on the instances are also unaffected.
In response to this call, the JVM TI event Class File Load Hook will be sent (if enabled), but no other JVM TI events will be sent.
The redefinition may change method bodies, the constant pool and attributes (unless explicitly prohibited). The redefinition must not add, remove or rename fields or methods, change the signatures of methods, change modifiers, or change inheritance. The redefinition must not change the NestHost, NestMembers, Record, or PermittedSubclasses attributes. These restrictions may be lifted in future versions. See the error return description below for information on error codes returned if an unsupported redefinition is attempted. The class file bytes are not verified or installed until they have passed through the chain of ClassFileLoadHook events, thus the returned error code reflects the result of the transformations applied to the bytes passed into class_definitions. If any error code is returned other than JVMTI_ERROR_NONE, none of the classes to be redefined will have a new definition installed. When this function returns (with the error code of JVMTI_ERROR_NONE) all of the classes to be redefined will have their new definitions installed.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
87
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_redefine_classes Can redefine classes with RedefineClasses.
Optional Features
can_redefine_any_class RedefineClasses can be called on any modifiable class. See IsModifiableClass. (can_redefine_classes must also be set)

jvmtiClassDefinition - Class redefinition description
FieldTypeDescription
klassjclass Class object for this class
class_byte_countjint Number of bytes defining class (below)
class_bytesconst unsigned char* Bytes defining class (in The Java™ Virtual Machine Specification, Chapter 4)
Parameters
NameTypeDescription
class_countjint The number of classes specified in class_definitions
class_definitionsconst jvmtiClassDefinition* The array of new class definitions
Agent passes in an array of class_count elements of jvmtiClassDefinition.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_redefine_classes. Use AddCapabilities.
JVMTI_ERROR_NULL_POINTER One of class_bytes is null.
JVMTI_ERROR_UNMODIFIABLE_CLASS An element of class_definitions cannot be modified. See IsModifiableClass.
JVMTI_ERROR_INVALID_CLASS An element of class_definitions is not a valid class.
JVMTI_ERROR_UNSUPPORTED_VERSION A new class file has a version number not supported by this VM.
JVMTI_ERROR_INVALID_CLASS_FORMAT A new class file is malformed (The VM would return a ClassFormatError).
JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION The new class file definitions would lead to a circular definition (the VM would return a ClassCircularityError).
JVMTI_ERROR_FAILS_VERIFICATION The class bytes fail verification.
JVMTI_ERROR_NAMES_DONT_MATCH The class name defined in a new class file is different from the name in the old class object.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED A new class file would require adding a method.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED A new class version changes a field.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED A direct superclass is different for a new class version, or the set of directly implemented interfaces is different.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED A new class version does not declare a method declared in the old class version.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED A new class version has unsupported differences in class attributes.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED A new class version has different modifiers.
JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED A method in the new class version has different modifiers than its counterpart in the old class version.
JVMTI_ERROR_UNMODIFIABLE_MODULE A module cannot be modified. See IsModifiableModule.
JVMTI_ERROR_ILLEGAL_ARGUMENT class_count is less than 0.
JVMTI_ERROR_NULL_POINTER class_definitions is a null pointer .

Object

Object functions: Object types:

Get Object Size

jvmtiError
GetObjectSize(jvmtiEnv* env,
            jobject object,
            jlong* size_ptr)
For the object indicated by object, return via size_ptr the size of the object. This size is an implementation-specific approximation of the amount of storage consumed by this object. It may include some or all of the object's overhead, and thus is useful for comparison within an implementation but not between implementations. The estimate may change during a single invocation of the JVM.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
154
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
objectjobject The object to query.
size_ptrjlong* On return, points to the object's size in bytes.
Agent passes a pointer to a jlong. On return, the jlong has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_OBJECT object is not an object.
JVMTI_ERROR_NULL_POINTER size_ptr is a null pointer .

Get Object Hash Code

jvmtiError
GetObjectHashCode(jvmtiEnv* env,
            jobject object,
            jint* hash_code_ptr)
For the object indicated by object, return via hash_code_ptr a hash code. This hash code could be used to maintain a hash table of object references, however, on some implementations this can cause significant performance impacts--in most cases tags will be a more efficient means of associating information with objects. This function guarantees the same hash code value for a particular object throughout its life
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
58
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
objectjobject The object to query.
hash_code_ptrjint* On return, points to the object's hash code.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_OBJECT object is not an object.
JVMTI_ERROR_NULL_POINTER hash_code_ptr is a null pointer .

Get Object Monitor Usage

typedef struct {
    jthread owner;
    jint entry_count;
    jint waiter_count;
    jthread* waiters;
    jint notify_waiter_count;
    jthread* notify_waiters;
} jvmtiMonitorUsage;
jvmtiError
GetObjectMonitorUsage(jvmtiEnv* env,
            jobject object,
            jvmtiMonitorUsage* info_ptr)
Get information about the object's monitor. The fields of the jvmtiMonitorUsage structure are filled in with information about usage of the monitor.
This function does not support getting information about an object's monitor when it is owned by a virtual thread. It also does not support returning a reference to virtual threads that are waiting to own a monitor or waiting to be notified.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
59
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_monitor_info Can GetObjectMonitorUsage

jvmtiMonitorUsage - Object monitor usage information
FieldTypeDescription
ownerjthread The platform thread owning this monitor, or null if owned by a virtual thread or not owned
entry_countjint The number of times the platform thread owning this monitor has entered it, or 0 if owned by a virtual thread or not owned
waiter_countjint The number of platform threads waiting to own this monitor, or 0 if only virtual threads are waiting or no threads are waiting
waitersjthread* The waiter_count waiting platform threads
notify_waiter_countjint The number of platform threads waiting to own this monitor, or 0 if only virtual threads are waiting to be notified or no threads are waiting to be notified
notify_waitersjthread* The notify_waiter_count platform threads waiting to be notified
Parameters
NameTypeDescription
objectjobject The object to query.
info_ptrjvmtiMonitorUsage* On return, filled with monitor information for the specified object.
Agent passes a pointer to a jvmtiMonitorUsage. On return, the jvmtiMonitorUsage has been set. The object returned in the field owner of jvmtiMonitorUsage is a JNI local reference and must be managed. The pointer returned in the field waiters of jvmtiMonitorUsage is a newly allocated array. The array should be freed with Deallocate. The objects returned in the field waiters of jvmtiMonitorUsage are JNI local references and must be managed. The pointer returned in the field notify_waiters of jvmtiMonitorUsage is a newly allocated array. The array should be freed with Deallocate. The objects returned in the field notify_waiters of jvmtiMonitorUsage are JNI local references and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_monitor_info. Use AddCapabilities.
JVMTI_ERROR_INVALID_OBJECT object is not an object.
JVMTI_ERROR_NULL_POINTER info_ptr is a null pointer .

Field

Field functions:

Get Field Name (and Signature)

jvmtiError
GetFieldName(jvmtiEnv* env,
            jclass klass,
            jfieldID field,
            char** name_ptr,
            char** signature_ptr,
            char** generic_ptr)
For the field indicated by klass and field, return the field name via name_ptr and field signature via signature_ptr.
Field signatures are defined in the JNI Specification and are referred to as field descriptors in The Java™ Virtual Machine Specification, Chapter 4.3.2.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
60
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class of the field to query.
fieldjfieldID The field to query.
name_ptr char ** On return, points to the field name, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If name_ptr is null pointer, the name is not returned.
signature_ptr char ** On return, points to the field signature, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If signature_ptr is null pointer, the signature is not returned.
generic_ptr char ** On return, points to the generic signature of the field, encoded as a modified UTF-8 string. If there is no generic signature attribute for the field, then, on return, points to null.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If generic_ptr is null pointer, the generic signature is not returned.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.

Get Field Declaring Class

jvmtiError
GetFieldDeclaringClass(jvmtiEnv* env,
            jclass klass,
            jfieldID field,
            jclass* declaring_class_ptr)
For the field indicated by klass and field return the class that defined it via declaring_class_ptr. The declaring class will either be klass, a superclass, or an implemented interface.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
61
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
fieldjfieldID The field to query.
declaring_class_ptrjclass* On return, points to the declaring class
Agent passes a pointer to a jclass. On return, the jclass has been set. The object returned by declaring_class_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.
JVMTI_ERROR_NULL_POINTER declaring_class_ptr is a null pointer .

Get Field Modifiers

jvmtiError
GetFieldModifiers(jvmtiEnv* env,
            jclass klass,
            jfieldID field,
            jint* modifiers_ptr)
For the field indicated by klass and field return the access flags via modifiers_ptr. Access flags are defined in The Java™ Virtual Machine Specification, Chapter 4.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
62
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
klassjclass The class to query.
fieldjfieldID The field to query.
modifiers_ptrjint* On return, points to the access flags.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.
JVMTI_ERROR_NULL_POINTER modifiers_ptr is a null pointer .

Is Field Synthetic

jvmtiError
IsFieldSynthetic(jvmtiEnv* env,
            jclass klass,
            jfieldID field,
            jboolean* is_synthetic_ptr)
For the field indicated by klass and field, return a value indicating whether the field is synthetic via is_synthetic_ptr. Synthetic fields are generated by the compiler but not present in the original source code.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
63
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_synthetic_attribute Can test if a field or method is synthetic - IsFieldSynthetic and IsMethodSynthetic
Parameters
NameTypeDescription
klassjclass The class of the field to query.
fieldjfieldID The field to query.
is_synthetic_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_synthetic_attribute. Use AddCapabilities.
JVMTI_ERROR_INVALID_CLASS klass is not a class object or the class has been unloaded.
JVMTI_ERROR_INVALID_FIELDID field is not a jfieldID.
JVMTI_ERROR_NULL_POINTER is_synthetic_ptr is a null pointer .

Method

Method functions: Method types: These functions provide information about a method (represented as a jmethodID) and set how methods are processed.

Obsolete Methods

The functions RetransformClasses and RedefineClasses can cause new versions of methods to be installed. An original version of a method is considered equivalent to the new version if: An original method version which is not equivalent to the new method version is called obsolete and is assigned a new method ID; the original method ID now refers to the new method version. A method ID can be tested for obsolescence with IsMethodObsolete.

Get Method Name (and Signature)

jvmtiError
GetMethodName(jvmtiEnv* env,
            jmethodID method,
            char** name_ptr,
            char** signature_ptr,
            char** generic_ptr)
For the method indicated by method, return the method name via name_ptr and method signature via signature_ptr.
Method signatures are defined in the JNI Specification and are referred to as method descriptors in The Java™ Virtual Machine Specification, Chapter 4.3.3. Note this is different than method signatures as defined in the Java Language Specification.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
64
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
name_ptr char ** On return, points to the method name, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If name_ptr is null pointer, the name is not returned.
signature_ptr char ** On return, points to the method signature, encoded as a modified UTF-8 string.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If signature_ptr is null pointer, the signature is not returned.
generic_ptr char ** On return, points to the generic signature of the method, encoded as a modified UTF-8 string. If there is no generic signature attribute for the method, then, on return, points to null.
Agent passes a pointer to a char*. On return, the char* points to a newly allocated array. The array should be freed with Deallocate. If generic_ptr is null pointer, the generic signature is not returned.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.

Get Method Declaring Class

jvmtiError
GetMethodDeclaringClass(jvmtiEnv* env,
            jmethodID method,
            jclass* declaring_class_ptr)
For the method indicated by method, return the class that defined it via declaring_class_ptr.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
65
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
declaring_class_ptrjclass* On return, points to the declaring class
Agent passes a pointer to a jclass. On return, the jclass has been set. The object returned by declaring_class_ptr is a JNI local reference and must be managed.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NULL_POINTER declaring_class_ptr is a null pointer .

Get Method Modifiers

jvmtiError
GetMethodModifiers(jvmtiEnv* env,
            jmethodID method,
            jint* modifiers_ptr)
For the method indicated by method, return the access flags via modifiers_ptr. Access flags are defined in The Java™ Virtual Machine Specification, Chapter 4.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
66
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
modifiers_ptrjint* On return, points to the access flags.
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NULL_POINTER modifiers_ptr is a null pointer .

Get Max Locals

jvmtiError
GetMaxLocals(jvmtiEnv* env,
            jmethodID method,
            jint* max_ptr)
For the method indicated by method, return the number of local variable slots used by the method, including the local variables used to pass parameters to the method on its invocation.
See max_locals in The Java™ Virtual Machine Specification, Chapter 4.7.3.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
68
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
max_ptrjint* On return, points to the maximum number of local slots
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NATIVE_METHOD method is a native method.
JVMTI_ERROR_NULL_POINTER max_ptr is a null pointer .

Get Arguments Size

jvmtiError
GetArgumentsSize(jvmtiEnv* env,
            jmethodID method,
            jint* size_ptr)
For the method indicated by method, return via max_ptr the number of local variable slots used by the method's arguments. Note that two-word arguments use two slots.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
69
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
size_ptrjint* On return, points to the number of argument slots
Agent passes a pointer to a jint. On return, the jint has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NATIVE_METHOD method is a native method.
JVMTI_ERROR_NULL_POINTER size_ptr is a null pointer .

Get Line Number Table

typedef struct {
    jlocation start_location;
    jint line_number;
} jvmtiLineNumberEntry;
jvmtiError
GetLineNumberTable(jvmtiEnv* env,
            jmethodID method,
            jint* entry_count_ptr,
            jvmtiLineNumberEntry** table_ptr)
For the method indicated by method, return a table of source line number entries. The size of the table is returned via entry_count_ptr and the table itself is returned via table_ptr.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
70
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_line_numbers Can get the line number table of a method

jvmtiLineNumberEntry - Line number table entry
FieldTypeDescription
start_locationjlocation the jlocation where the line begins
line_numberjint the line number
Parameters
NameTypeDescription
methodjmethodID The method to query.
entry_count_ptrjint* On return, points to the number of entries in the table
Agent passes a pointer to a jint. On return, the jint has been set.
table_ptrjvmtiLineNumberEntry** On return, points to the line number table pointer.
Agent passes a pointer to a jvmtiLineNumberEntry*. On return, the jvmtiLineNumberEntry* points to a newly allocated array of size *entry_count_ptr. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_line_numbers. Use AddCapabilities.
JVMTI_ERROR_ABSENT_INFORMATION Class information does not include line numbers.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NATIVE_METHOD method is a native method.
JVMTI_ERROR_NULL_POINTER entry_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER table_ptr is a null pointer .

Get Method Location

jvmtiError
GetMethodLocation(jvmtiEnv* env,
            jmethodID method,
            jlocation* start_location_ptr,
            jlocation* end_location_ptr)
For the method indicated by method, return the beginning and ending addresses through start_location_ptr and end_location_ptr. In a conventional bytecode indexing scheme, start_location_ptr will always point to zero and end_location_ptr will always point to the bytecode count minus one.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
71
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
start_location_ptrjlocation* On return, points to the first location, or -1 if location information is not available. If the information is available and GetJLocationFormat returns JVMTI_JLOCATION_JVMBCI then this will always be zero.
Agent passes a pointer to a jlocation. On return, the jlocation has been set.
end_location_ptrjlocation* On return, points to the last location, or -1 if location information is not available.
Agent passes a pointer to a jlocation. On return, the jlocation has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_ABSENT_INFORMATION Class information does not include method sizes.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NATIVE_METHOD method is a native method.
JVMTI_ERROR_NULL_POINTER start_location_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER end_location_ptr is a null pointer .

Get Local Variable Table

typedef struct {
    jlocation start_location;
    jint length;
    char* name;
    char* signature;
    char* generic_signature;
    jint slot;
} jvmtiLocalVariableEntry;
jvmtiError
GetLocalVariableTable(jvmtiEnv* env,
            jmethodID method,
            jint* entry_count_ptr,
            jvmtiLocalVariableEntry** table_ptr)
Return local variable information.
Phase
Callback Safe
Position
Since
may only be called during the live phase
No
72
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_access_local_variables Can set and get local variables

jvmtiLocalVariableEntry - Local variable table entry
FieldTypeDescription
start_locationjlocation The code array index where the local variable is first valid (that is, where it must have a value).
lengthjint The length of the valid section for this local variable. The last code array index where the local variable is valid is start_location + length.
namechar* The local variable name, encoded as a modified UTF-8 string.
signaturechar* The local variable's type signature, encoded as a modified UTF-8 string. The signature format is the same as that defined in The Java™ Virtual Machine Specification, Chapter 4.3.2.
generic_signaturechar* The local variable's generic signature, encoded as a modified UTF-8 string. The value of this field will be null for any local variable which does not have a generic type.
slotjint The local variable's slot. See Local Variables.
Parameters
NameTypeDescription
methodjmethodID The method to query.
entry_count_ptrjint* On return, points to the number of entries in the table
Agent passes a pointer to a jint. On return, the jint has been set.
table_ptrjvmtiLocalVariableEntry** On return, points to an array of local variable table entries.
Agent passes a pointer to a jvmtiLocalVariableEntry*. On return, the jvmtiLocalVariableEntry* points to a newly allocated array of size *entry_count_ptr. The array should be freed with Deallocate. The pointers returned in the field name of jvmtiLocalVariableEntry are newly allocated arrays. The arrays should be freed with Deallocate. The pointers returned in the field signature of jvmtiLocalVariableEntry are newly allocated arrays. The arrays should be freed with Deallocate. The pointers returned in the field generic_signature of jvmtiLocalVariableEntry are newly allocated arrays. The arrays should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_access_local_variables. Use AddCapabilities.
JVMTI_ERROR_ABSENT_INFORMATION Class information does not include local variable information.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NATIVE_METHOD method is a native method.
JVMTI_ERROR_NULL_POINTER entry_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER table_ptr is a null pointer .

Get Bytecodes

jvmtiError
GetBytecodes(jvmtiEnv* env,
            jmethodID method,
            jint* bytecode_count_ptr,
            unsigned char** bytecodes_ptr)
For the method indicated by method, return the bytecodes that implement the method. The number of bytecodes is returned via bytecode_count_ptr. The bytecodes themselves are returned via bytecodes_ptr.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
75
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_bytecodes Can get bytecodes of a method GetBytecodes
Parameters
NameTypeDescription
methodjmethodID The method to query.
bytecode_count_ptrjint* On return, points to the length of the bytecode array
Agent passes a pointer to a jint. On return, the jint has been set.
bytecodes_ptrunsigned char** On return, points to the pointer to the bytecode array
Agent passes a pointer to a unsigned char*. On return, the unsigned char* points to a newly allocated array of size *bytecode_count_ptr. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_bytecodes. Use AddCapabilities.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NATIVE_METHOD method is a native method.
JVMTI_ERROR_NULL_POINTER bytecode_count_ptr is a null pointer .
JVMTI_ERROR_NULL_POINTER bytecodes_ptr is a null pointer .

Is Method Native

jvmtiError
IsMethodNative(jvmtiEnv* env,
            jmethodID method,
            jboolean* is_native_ptr)
For the method indicated by method, return a value indicating whether the method is native via is_native_ptr
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
76
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method to query.
is_native_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NULL_POINTER is_native_ptr is a null pointer .

Is Method Synthetic

jvmtiError
IsMethodSynthetic(jvmtiEnv* env,
            jmethodID method,
            jboolean* is_synthetic_ptr)
For the method indicated by method, return a value indicating whether the method is synthetic via is_synthetic_ptr. Synthetic methods are generated by the compiler but not present in the original source code.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
77
1.0
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_get_synthetic_attribute Can test if a field or method is synthetic - IsFieldSynthetic and IsMethodSynthetic
Parameters
NameTypeDescription
methodjmethodID The method to query.
is_synthetic_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_get_synthetic_attribute. Use AddCapabilities.
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NULL_POINTER is_synthetic_ptr is a null pointer .

Is Method Obsolete

jvmtiError
IsMethodObsolete(jvmtiEnv* env,
            jmethodID method,
            jboolean* is_obsolete_ptr)
Determine if a method ID refers to an obsolete method version.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
91
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
methodjmethodID The method ID to query.
is_obsolete_ptrjboolean* On return, points to the boolean result of this function.
Agent passes a pointer to a jboolean. On return, the jboolean has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_METHODID method is not a jmethodID.
JVMTI_ERROR_NULL_POINTER is_obsolete_ptr is a null pointer .

Set Native Method Prefix

jvmtiError
SetNativeMethodPrefix(jvmtiEnv* env,
            const char* prefix)
This function modifies the failure handling of native method resolution by allowing retry with a prefix applied to the name. When used with the ClassFileLoadHook event, it enables native methods to be instrumented.
Since native methods cannot be directly instrumented (they have no bytecodes), they must be wrapped with a non-native method which can be instrumented. For example, if we had: 
native boolean foo(int x);
We could transform the class file (with the ClassFileLoadHook event) so that this becomes: 
                    boolean foo(int x) {
  ... record entry to foo ...
  return wrapped_foo(x);
}

native boolean wrapped_foo(int x);
Where foo becomes a wrapper for the actual native method with the appended prefix "wrapped_". Note that "wrapped_" would be a poor choice of prefix since it might conceivably form the name of an existing method thus something like "$$$MyAgentWrapped$$$_" would be better but would make these examples less readable.
The wrapper will allow data to be collected on the native method call, but now the problem becomes linking up the wrapped method with the native implementation. That is, the method wrapped_foo needs to be resolved to the native implementation of foo, which might be: 
Java_somePackage_someClass_foo(JNIEnv* env, jint x)
This function allows the prefix to be specified and the proper resolution to occur. Specifically, when the standard resolution fails, the resolution is retried taking the prefix into consideration. There are two ways that resolution occurs, explicit resolution with the JNI function RegisterNatives and the normal automatic resolution. For RegisterNatives, the VM will attempt this association: 
method(foo) -> nativeImplementation(foo)
When this fails, the resolution will be retried with the specified prefix prepended to the method name, yielding the correct resolution: 
method(wrapped_foo) -> nativeImplementation(foo)
For automatic resolution, the VM will attempt: 
method(wrapped_foo) -> nativeImplementation(wrapped_foo)
When this fails, the resolution will be retried with the specified prefix deleted from the implementation name, yielding the correct resolution: 
method(wrapped_foo) -> nativeImplementation(foo)
Note that since the prefix is only used when standard resolution fails, native methods can be wrapped selectively.
Since each JVM TI environment is independent and can do its own transformation of the bytecodes, more than one layer of wrappers may be applied. Thus each environment needs its own prefix. Since transformations are applied in order, the prefixes, if applied, will be applied in the same order. The order of transformation application is described in the ClassFileLoadHook event. Thus if three environments applied wrappers, foo might become $env3_$env2_$env1_foo. But if, say, the second environment did not apply a wrapper to foo it would be just $env3_$env1_foo. To be able to efficiently determine the sequence of prefixes, an intermediate prefix is only applied if its non-native wrapper exists. Thus, in the last example, even though $env1_foo is not a native method, the $env1_ prefix is applied since $env1_foo exists.
Since the prefixes are used at resolution time and since resolution may be arbitrarily delayed, a native method prefix must remain set as long as there are corresponding prefixed native methods.
Phase
Callback Safe
Position
Since
may be called during any phase
No
73
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_set_native_method_prefix Can set prefix to be applied when native method cannot be resolved - SetNativeMethodPrefix and SetNativeMethodPrefixes
Parameters
NameTypeDescription
prefixconst char * The prefix to apply, encoded as a modified UTF-8 string.
Agent passes in an array of char. If prefix is null pointer, any existing prefix in this environment is cancelled .
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_set_native_method_prefix. Use AddCapabilities.

Set Native Method Prefixes

jvmtiError
SetNativeMethodPrefixes(jvmtiEnv* env,
            jint prefix_count,
            char** prefixes)
For a normal agent, SetNativeMethodPrefix will provide all needed native method prefixing. For a meta-agent that performs multiple independent class file transformations (for example as a proxy for another layer of agents) this function allows each transformation to have its own prefix. The prefixes are applied in the order supplied and are processed in the same manner as described for the application of prefixes from multiple JVM TI environments in SetNativeMethodPrefix.
Any previous prefixes are replaced. Thus, calling this function with a prefix_count of 0 disables prefixing in this environment.
SetNativeMethodPrefix and this function are the two ways to set the prefixes. Calling SetNativeMethodPrefix with a prefix is the same as calling this function with prefix_count of 1. Calling SetNativeMethodPrefix with a null pointer is the same as calling this function with prefix_count of 0.
Phase
Callback Safe
Position
Since
may be called during any phase
No
74
1.1
Capabilities
Optional Functionality: might not be implemented for all virtual machines. The following capability (as returned by GetCapabilities) must be true to use this function.
CapabilityEffect
can_set_native_method_prefix Can set prefix to be applied when native method cannot be resolved - SetNativeMethodPrefix and SetNativeMethodPrefixes
Parameters
NameTypeDescription
prefix_countjint The number of prefixes to apply.
prefixes char ** The prefixes to apply for this environment, each encoded as a modified UTF-8 string.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_MUST_POSSESS_CAPABILITY The environment does not possess the capability can_set_native_method_prefix. Use AddCapabilities.
JVMTI_ERROR_ILLEGAL_ARGUMENT prefix_count is less than 0.
JVMTI_ERROR_NULL_POINTER prefixes is a null pointer .

Raw Monitor

Raw Monitor functions:

Create Raw Monitor

jvmtiError
CreateRawMonitor(jvmtiEnv* env,
            const char* name,
            jrawMonitorID* monitor_ptr)
Create a raw monitor.
Phase
Callback Safe
Position
Since
may only be called during the OnLoad or the live phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
31
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
nameconst char* A name to identify the monitor, encoded as a modified UTF-8 string.
Agent passes in an array of char.
monitor_ptrjrawMonitorID* On return, points to the created monitor.
Agent passes a pointer to a jrawMonitorID. On return, the jrawMonitorID has been set.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER name is a null pointer .
JVMTI_ERROR_NULL_POINTER monitor_ptr is a null pointer .

Destroy Raw Monitor

jvmtiError
DestroyRawMonitor(jvmtiEnv* env,
            jrawMonitorID monitor)
Destroy the raw monitor. If the monitor being destroyed has been entered by this thread, it will be exited before it is destroyed. If the monitor being destroyed has been entered by another thread, an error will be returned and the monitor will not be destroyed.
Phase
Callback Safe
Position
Since
may only be called during the OnLoad or the live phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
32
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
monitorjrawMonitorID The monitor
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NOT_MONITOR_OWNER Not monitor owner
JVMTI_ERROR_INVALID_MONITOR monitor is not a jrawMonitorID.

Raw Monitor Enter

jvmtiError
RawMonitorEnter(jvmtiEnv* env,
            jrawMonitorID monitor)
Gain exclusive ownership of a raw monitor. The same thread may enter a monitor more then once. The thread must exit the monitor the same number of times as it is entered. If a monitor is entered during OnLoad (before attached threads exist) and has not exited when attached threads come into existence, the enter is considered to have occurred on the main thread.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
33
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
monitorjrawMonitorID The monitor
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_INVALID_MONITOR monitor is not a jrawMonitorID.

Raw Monitor Exit

jvmtiError
RawMonitorExit(jvmtiEnv* env,
            jrawMonitorID monitor)
Release exclusive ownership of a raw monitor.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
34
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
monitorjrawMonitorID The monitor
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NOT_MONITOR_OWNER Not monitor owner
JVMTI_ERROR_INVALID_MONITOR monitor is not a jrawMonitorID.

Raw Monitor Wait

jvmtiError
RawMonitorWait(jvmtiEnv* env,
            jrawMonitorID monitor,
            jlong millis)
Wait for notification of the raw monitor.
Causes the current thread to wait until either another thread calls RawMonitorNotify or RawMonitorNotifyAll for the specified raw monitor, or the specified timeout has elapsed.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
35
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
monitorjrawMonitorID The monitor
millisjlong The timeout, in milliseconds. If the timeout is zero, then real time is not taken into consideration and the thread simply waits until notified.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NOT_MONITOR_OWNER Not monitor owner
JVMTI_ERROR_INTERRUPT Wait was interrupted, try again
JVMTI_ERROR_INVALID_MONITOR monitor is not a jrawMonitorID.

Raw Monitor Notify

jvmtiError
RawMonitorNotify(jvmtiEnv* env,
            jrawMonitorID monitor)
Notify a single thread waiting on the raw monitor.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
36
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
monitorjrawMonitorID The monitor
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NOT_MONITOR_OWNER Not monitor owner
JVMTI_ERROR_INVALID_MONITOR monitor is not a jrawMonitorID.

Raw Monitor Notify All

jvmtiError
RawMonitorNotifyAll(jvmtiEnv* env,
            jrawMonitorID monitor)
Notify all threads waiting on the raw monitor.
Phase
Callback Safe
Position
Since
may be called during any phase
This function may be called from the callbacks to the Heap iteration functions, or from the event handlers for the GarbageCollectionStart, GarbageCollectionFinish, and ObjectFree events.
37
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
monitorjrawMonitorID The monitor
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NOT_MONITOR_OWNER Not monitor owner
JVMTI_ERROR_INVALID_MONITOR monitor is not a jrawMonitorID.

JNI Function Interception

JNI Function Interception functions: Provides the ability to intercept and resend Java Native Interface (JNI) function calls by manipulating the JNI function table. See JNI Functions in the Java Native Interface Specification.
The following example illustrates intercepting the NewGlobalRef JNI call in order to count reference creation. 
JNIEnv original_jni_Functions;
JNIEnv redirected_jni_Functions;
int my_global_ref_count = 0;

jobject
MyNewGlobalRef(JNIEnv *jni_env, jobject lobj) {
   ++my_global_ref_count;
   return originalJNIFunctions->NewGlobalRef(env, lobj);
}

void
myInit() {
   jvmtiError err;

   err = (*jvmti_env)->GetJNIFunctionTable(jvmti_env, &original_jni_Functions);
   if (err != JVMTI_ERROR_NONE) {
      die();
   }
   err = (*jvmti_env)->GetJNIFunctionTable(jvmti_env, &redirected_jni_Functions);
   if (err != JVMTI_ERROR_NONE) {
      die();
   }
   redirectedJNIFunctions->NewGlobalRef = MyNewGlobalRef;
      err = (*jvmti_env)->SetJNIFunctionTable(jvmti_env, redirected_jni_Functions);
   if (err != JVMTI_ERROR_NONE) {
      die();
   }
}
Sometime after myInit is called the user's JNI code is executed which makes the call to create a new global reference. Instead of going to the normal JNI implementation the call goes to myNewGlobalRef. Note that a copy of the original function table is kept so that the normal JNI function can be called after the data is collected. Note also that any JNI functions which are not overwritten will behave normally.

Set JNI Function Table

jvmtiError
SetJNIFunctionTable(jvmtiEnv* env,
            const jniNativeInterface* function_table)
Set the JNI function table in all current and future JNI environments. As a result, all future JNI calls are directed to the specified functions. Use GetJNIFunctionTable to get the function table to pass to this function. For this function to take effect the updated table entries must be used by the JNI clients. Since the table is defined const some compilers may optimize away the access to the table, thus preventing this function from taking effect. The table is copied--changes to the local copy of the table have no effect. This function affects only the function table, all other aspects of the environment are unaffected. See the examples above.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
120
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
function_tableconst jniNativeInterface * Points to the new JNI function table.
Agent passes in a pointer to jniNativeInterface.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER function_table is a null pointer .

Get JNI Function Table

jvmtiError
GetJNIFunctionTable(jvmtiEnv* env,
            jniNativeInterface** function_table)
Get the JNI function table. The JNI function table is copied into allocated memory. If SetJNIFunctionTable has been called, the modified (not the original) function table is returned. Only the function table is copied, no other aspects of the environment are copied. See the examples above.
Phase
Callback Safe
Position
Since
may only be called during the start or the live phase
No
121
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
function_table jniNativeInterface ** On return, *function_table points a newly allocated copy of the JNI function table.
Agent passes a pointer to a jniNativeInterface*. On return, the jniNativeInterface* points to a newly allocated array. The array should be freed with Deallocate.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_NULL_POINTER function_table is a null pointer .

Event Management

Event Management functions: Event Management types:

Set Event Callbacks

jvmtiError
SetEventCallbacks(jvmtiEnv* env,
            const jvmtiEventCallbacks* callbacks,
            jint size_of_callbacks)
Set the functions to be called for each event. The callbacks are specified by supplying a replacement function table. The function table is copied--changes to the local copy of the table have no effect. This is an atomic action, all callbacks are set at once. No events are sent before this function is called. When an entry is null or when the event is beyond size_of_callbacks no event is sent. Details on events are described later in this document. An event must be enabled and have a callback in order to be sent--the order in which this function and SetEventNotificationMode are called does not affect the result.
Phase
Callback Safe
Position
Since
may only be called during the OnLoad or the live phase
No
122
1.0
Capabilities
Required Functionality
Parameters
NameTypeDescription
callbacksconst jvmtiEventCallbacks * The new event callbacks.
Agent passes in a pointer to jvmtiEventCallbacks. If callbacks is null pointer, remove the existing callbacks.
size_of_callbacksjint sizeof(jvmtiEventCallbacks)--for version compatibility.
Errors
This function returns either a universal error or one of the following errors
ErrorDescription
JVMTI_ERROR_ILLEGAL_ARGUMENT size_of_callbacks is less than 0.

Set Event Notification Mode

typedef enum {
    JVMTI_ENABLE = 1,
    JVMTI_DISABLE = 0
} jvmtiEventMode;
jvmtiError
SetEventNotificationMode(jvmtiEnv* env,
            jvmtiEventMode mode,
            jvmtiEvent event_type,
            jthread event_thread,
             ...)
Control the generation of events.
Event Enable/Disable (jvmtiEventMode)
ConstantValueDescription
JVMTI_ENABLE1 If mode is JVMTI_ENABLE, the event event_type will be enabled
JVMTI_DISABLE0 If mode is JVMTI_DISABLE, the event event_type will be disabled
If event_thread is null, the event is enabled or disabled globally; otherwise, it is enabled or disabled for a particular thread. An event is generated for a particular thread if it is enabled either at the thread or global levels.
See below for information on specific events.
The following events cannot be controlled at the thread level through this function.
Initially, no events are enabled at either the thread level or the global level.
Any needed capabilities (see Event Enabling Capabilities below) must be possessed before calling this function.
Details on events are described below.
Phase
Callback Safe
Position
Since
may only be called during the OnLoad or the live phase
No
2
1.0
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Capabilities
Required Functionality