Using dbx Commands in Java Mode

When you are using dbx to debug a mixture of Java and native code, dbx commands fall into several categories:

• Commands that accept the same arguments and operate the same way in Java mode or JNI mode as in native mode. See Commands With Identical Syntax and Functionality in Java Mode and Native Mode.

• Commands that have arguments that are valid only in Java mode or JNI mode, as well as arguments that are valid only in native mode. See Commands With Different Syntax in Java Mode.

• Commands that are valid only in Java mode or JNI mode. See Commands Valid Only in Java Mode.

Any commands not included in one of these categories work only in native mode.

Java Expression Evaluation in dbx Commands

The Java expression evaluator used in most dbx commands supports the following constructs:

• All literals

• All names and field accesses

• this and super

• Array accesses

• Casts

• Conditional binary operations

• Method calls

• Other unary/binary operations

• Assignment to variables or fields

• instanceof operator

• Array length operator

The Java expression evaluator does not support the following constructs:

• Qualified this, for example, <ClassName>.this

• Class instance creation expressions

• Array creation expressions

• String concatenation operator

• Conditional operator ? :

• Compound assignment operators, for example x += 3

A particularly useful way of inspecting the state of your Java application is using the watch facility in the IDE or dbxtool.

Do not depend on precise value semantics in expressions that do more than just inspect data.

Static and Dynamic Information Used by dbx Commands

Much of the information about a Java application is normally available only after the JVM software has started, and is unavailable after the Java application has finished executing. However, when you debug a Java application with dbx, dbx gleans some of the information it needs from class files and JAR files that are part of the system class path and user class path before it starts the JVM software. This information enables dbx to do better error checking on breakpoints before you run the application.

Some Java classes and their attributes might not be accessible through the class path. dbx can inspect and step through these classes, and the expression parser can access them once they are loaded at runtime. However, the information it gathers is temporary and is no longer available after the JVM software terminates.

Some information that dbx needs to debug your Java application is not recorded anywhere so dbx skims Java source files to derive this information as it is debugging your code.

Commands With Identical Syntax and Functionality in Java Mode and Native Mode

The dbx commands listed in the following table have the same syntax and perform the same operations in Java mode as in native mode.

Command Functionality attach Attaches dbx to a running process, stopping execution and putting the program under debugging control cont Causes the process to continue execution dbxenv List or set dbxenv variables delete Deletes breakpoints and other events down Moves down the call stack (away from main) dump Prints all variables local to a procedure or method file Lists or changes the current file frame Lists or changes the current stack frame number handler Modifies event handlers (breakpoints) import Imports commands from a dbx command library line Lists or changes the current line number list Displays lines of a source file next Steps one source line (steps over calls) pathmap Maps one path name to another for finding source files and the like proc Displays the status of the current process prog Manages programs being debugged and their attributes quit Exits dbx rerun Runs the program with no arguments runargs Changes the arguments of the target process status Lists the event handlers (breakpoints) step up Steps up and out of the current function or method stepi Steps one machine instruction (steps into calls) up Moves up the call stack (toward main) whereami Displays the current source line

Commands With Different Syntax in Java Mode

The dbx commands listed in the following table have different syntax for Java debugging than for native code debugging and operate differently in Java mode than in native mode.

Command Native Mode Functionality Java Mode Functionality assign Assigns a new value to a program variable Assigns a new value to a local variable or parameter call Calls a procedure Calls a method dbx Starts dbx Starts dbx debug Loads the specified application and begins debugging the application Loads the specified Java application, checks for the existence of the class file, and begins debugging the application detach Releases the target process from dbx’s control Releases the target process from dbx’s control display Evaluates and prints expressions at every stopping point Evaluates and prints expressions, local variables, or parameters at every stopping point files Lists file names that match a regular expression Lists all of the Java source files known to dbx func Lists or changes the current function Lists or changes the current method next Steps one source line (stepping over calls) Steps one source line (stepping over calls) print Prints the value of an expression Prints the value of an expression, local variable, or parameter run Runs the program with arguments Runs the program with arguments step Steps one source line or statement (stepping into calls) Steps one source line or statement (stepping into calls) stop Sets a source-level breakpoint Sets a source-level breakpoint thread Lists or changes the current thread Lists or changes the current thread threads Lists all threads Lists all threads trace Shows executed source lines, function calls, or variable changes Shows executed source lines, function calls, or variable changes undisplay Undoes display commands Undoes display commands whatis Prints the type of expression or declaration of type Prints the declaration of an identifier when Executes commands when a specified event occurs Executes commands when a specified event occurs where Prints the call stack Prints the call stack

Commands Valid Only in Java Mode

The dbx commands listed in the following table are valid only in Java mode or JNI mode.

Command Functionality java Used when dbx is in JNI mode to indicate that the Java version of a specified command is to be executed jclasses Prints the names of all Java classes known to dbx when you give the command joff Switches dbx from Java mode or JNI mode to native mode jon Switches dbx from native mode to Java mode jpkgs Prints the names of all Java packages known to dbx when you give the command native Used when dbx is in Java mode to indicate that the native version of a specified command is to be executed