Re: problem in glibc backtrace done inside nptl library

["Neal H. Walfield" <neal at walfield dot org>]

At Tue, 17 Jun 2008 15:27:38 +0200,
Vinu Rajashekhar wrote:
> 
> Hi,
>      I am working on adding some code to the nptl library,
> the code is in C++ and I have added the code to the nptl library,
> changed the makefiles to compile it with nptl.
> 
> I have instrumented pthread_mutex_lock , which calls a function from my
> code and inside I do a backtrace, but in the backtrace I dont get all
> the function names.
> 
> I want to know if the problem is because of the -rdynamic flag,
> because I am using it
> in both the build phase and compiling the binary and also I did the
> ldd to confirm its using
> the new libraries, compiled with my sources.
> 
> Heres the backtrace I get after using backtrace_symbols
> 
> /home/vinu/glibc/local/lib
> /libpthread.so.0 [0xb7f11820]
> /home/vinu/glibc/local/lib/libpthread.so.0 [0xb7f05e0e]
> /home/vinu/glibc/local/lib/libpthread.so.0 [0xb7f05ff7]
> /home/vinu/glibc/local/lib/libpthread.so.0(pthread_mutex_lock+0x90) [0xb7eef600]
> ./a.out(thr_fn0+0x12) [0x80487a6]
> /home/vinu/glibc/local/lib/libpthread.so.0 [0xb7eed347]
> /home/vinu/glibc/local/lib/libc.so.6(clone+0x5e) [0xb7e749ae]
> 
> I want to get the function names of the other functions. The funny thing is
> gdb is able to do it, then why not glibc backtrace ?

It may be that the functions that you are not seeing in your trace are
inlined.  This is because backtrace just returns the return addresses
that are on the stack; inlined functions are not executed as the
result of a call.

It is possible from looking at the binary and the debugging symbols to
figure this out.  This is what gdb does.  Another tool that also does
this is addr2line.  If this shows you what gdb shows you, then the
above is likely your problem.

Neal