gdb: Thread-Specific Breakpoints
5.5.4 Thread-Specific Breakpoints
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When your program has multiple threads (
Debugging Programs with
Multiple Threads Threads.), you can choose whether to set breakpoints
on all threads, or on a particular thread.
'break LOCATION thread THREAD-ID'
'break LOCATION thread THREAD-ID if ...'
LOCATION specifies source lines; there are several ways of writing
them (Specify Location), but the effect is always to
specify some source line.
Use the qualifier 'thread THREAD-ID' with a breakpoint command to
specify that you only want GDB to stop the program when a
particular thread reaches this breakpoint. The THREAD-ID specifier
is one of the thread identifiers assigned by GDB, shown in the
first column of the 'info threads' display.
If you do not specify 'thread THREAD-ID' when you set a breakpoint,
the breakpoint applies to _all_ threads of your program.
You can use the 'thread' qualifier on conditional breakpoints as
well; in this case, place 'thread THREAD-ID' before or after the
breakpoint condition, like this:
(gdb) break frik.c:13 thread 28 if bartab > lim
Thread-specific breakpoints are automatically deleted when GDB
detects the corresponding thread is no longer in the thread list. For
example:
(gdb) c
Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
There are several ways for a thread to disappear, such as a regular
thread exit, but also when you detach from the process with the 'detach'
command (Debugging an Already-running Process Attach.), or if GDB
loses the remote connection (Remote Debugging), etc. Note that
with some targets, GDB is only able to detect a thread has exited when
the user explictly asks for the thread list with the 'info threads'
command.
Info Catalog
gdb: Background Execution
gdb: Thread Stops
gdb: Interrupted System Calls