2.0.0-1.6 (Jun 18th, 2021)

New features:

Instruction offsets are printed as 4 digit values to accommodate the larger size of BPF programs used to implement probe programs.
String constants can be used as values in D clauses, and variables can hold string values. Built-in variables that hold string data can be assigned to variables and they can be used as values in expressions and as action arguments.
The trace() action supports strings.
The strlen() subroutine has been implemented.
The following built-in variables are now supported: probeprov, probemod, probefunc, probename, caller, stackdepth, ucaller, ustackdepth, errno, and walltimestamp.
The following actions have been implemented: stack(), ustack(), umod(), usym(), and uaddr().

Bugfixes:

The storage size was not always set correctly for global and local variables causing data corruption. When variables are not declared explicitly, their datatype may not be known until their first use. The storage size is now always set based on the explicit or discovered datatype of the variable.
Built-in variables are implemented as global variables within a specific variable ID range. Their value is not stored in the global variable storage area and they therefore do not have a storage offset. The variable listing in the disassembly output was printing -1 as offset. The offset will no longer be printed for built-in variables.
A memory leak related to the ERROR probe has been fixed.
Relocations of 64-bit data items were being truncated to the lower 32 bits. This has been fixed.
Storing data in an aggregation was considered a data recording action. This resulted in probe firings being reported by the consumer for clauses that do not actually store data in the probe output buffer. This behaviour was not intended. Aggregation data generation is no longer a data recording action.

Internal changes:

Global and local variables are now stored more efficiently by taking into account their size and alignment requirements.
Probe descriptions (id, provider name, module name, function name, and probe name) are now stored in the 'probes' BPF map. The values are offsets into the string constant table.
The string constant table is loaded into the 'strtab' BPF map as the value of the singleton element with key 0.
String hash value calculations have been unified into a single function that is called from all code that needs it.
Variable length integer support has been added. It will primarily be used to store the length of strings inline with the character stream.
The memory copy function (implemented as pre-compiled C code, compiled to BPF) has been optimized and has been made more robust.

Testsuite changes:

Various tests have been moved from XFAIL to to PASS status in response to the implementation of new features and in view of some bug fixes.
Various tests were improved.

Known problems:

The assignment of values of a datatype that is larger than 256 bytes does not currently work due to limitations in the memory copy implementation.
While the DTrace option to set a specific maximum string size is accepted by the command line tool, settings beyond 256 bytes do not work correctly.
The -Z option (allowing clauses that do not match any available probe) does not allow for registering a clause to be enabled at a later time when the probe becomes available.