Re: [PATCH 2/2] Add test for fast tracepoint enable/disable

Yao Qi
2016-04-01T13:36:55Z

Simon Marchi <simon.marchi@ericsson.com> writes:

> Good question. Because the setup for testing fast tracepoints is
> tedious, I always
> use ftrace-lock.exp as a template, because it is relatively short.
> ftrace-lock.exp
> uses gdb_compile_pthreads. I think it makes sense, because the IPA
> starts a helper
> thread with pthread_create.

gdb_compile_pthreads is used in ftrace-lock.exp because ftrace-lock.c is
a multi-threaded program, but ftrace-enable-disable.c isn't. The
program to be tested is running in one thread, and it doesn't have any
interaction with the helper thread.

>
> Note that it still builds fine with gdb_compile instead of gdb_compile_pthreads,
> probably because libinproctrace.so has a DT_NEEDED for libpthreads.so,
> so it gets
> pulled in. But using gdb_compile_pthreads should add -pthread to the
> CFLAGS, which
> may impact compilation (e.g. choose re-entrant versions of functions).

Using IPA/fast tracepoint shouldn't affect how the program is compiled.
User is writing and debugging a single thread program, and he/she wants
to use fast tracepoint to debug. He/She shouldn't recompile the program
with -lpthreads or -pthreads, what needed here is to let IPA be loaded with
the program.

>
> However, I just noticed that the command line includes -lpthreads
> instead of -pthreads:
>
> spawn gcc -Wl,--no-as-needed
> /home/emaisin/build/binutils-gdb/gdb/testsuite/../../../../src/binutils-gdb/gdb/testsuite/gdb.trace/ftrace-enable-disable.c
> \
> /home/emaisin/build/binutils-gdb/gdb/testsuite/../gdbserver/libinproctrace.so
> -g \
> -lpthread -lm -o \
> /home/emaisin/build/binutils-gdb/gdb/testsuite/outputs/gdb.trace/ftrace-enable-disable/ftrace-enable-disable
>
> I think that to be more "correct", we should try -pthread before -lpthread in
> gdb_compile_pthreads...

I am not sure, it is a separate issue, this applies to all test cases
compiled with gdb_compile_pthreads.

--
Yao (齐尧)