gdb: Tracepoints
13 Tracepoints
**************
In some applications, it is not feasible for the debugger to interrupt
the program's execution long enough for the developer to learn anything
helpful about its behavior. If the program's correctness depends on its
real-time behavior, delays introduced by a debugger might cause the
program to change its behavior drastically, or perhaps fail, even when
the code itself is correct. It is useful to be able to observe the
program's behavior without interrupting it.
Using GDB's 'trace' and 'collect' commands, you can specify locations
in the program, called "tracepoints", and arbitrary expressions to
evaluate when those tracepoints are reached. Later, using the 'tfind'
command, you can examine the values those expressions had when the
program hit the tracepoints. The expressions may also denote objects in
memory--structures or arrays, for example--whose values GDB should
record; while visiting a particular tracepoint, you may inspect those
objects as if they were in memory at that moment. However, because GDB
records these values without interacting with you, it can do so quickly
and unobtrusively, hopefully not disturbing the program's behavior.
The tracepoint facility is currently available only for remote
targets. 
Targets. In addition, your remote target must know
how to collect trace data. This functionality is implemented in the
remote stub; however, none of the stubs distributed with GDB support
tracepoints as of this writing. The format of the remote packets used
to implement tracepoints are described in Tracepoint Packets.
It is also possible to get trace data from a file, in a manner
reminiscent of corefiles; you specify the filename, and use 'tfind' to
search through the file. Trace Files, for more details.
This chapter describes the tracepoint commands and features.
Menu
Info Catalog
gdb: Macros
gdb: Top
gdb: Overlays