Re: Why isn't __pthread_unwind linked?

[Nick Clifton <nickc at redhat dot com>]

Hi Toru UCHIYAMA,

> But if pthread program using pthread_exit() is compiled and
> performed, segmentation fault will occur.  A __pthread_unwind
> function is assigned to the 0x0x10000000.

I assume that you have traced the segmentation fault in pthread_exit()
to the call to __pthread_unwind() ?


> Of course, libpthread.a contains unwind.o. and the extract of a
> result which performed nm -a is shown below.

> 00000080 W __pthread_unwind

> '--verbose' print is below.
> attempt to open /home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a succeeded
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)pthread_create.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)pthread_exit.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)pthread_join.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)cleanup_compat.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)cancellation.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)lowlevellock.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)init.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)events.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)pthread_once.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)sigaction.o
> (/home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libpthread.a)errno-loc.o
> attempt to open /home/xgcc/exper/1001/powerpc-405-linux-gnu/lib/libgcc.a failed

> Why isn't __pthread_unwind linked ? Any ideas ?

It must be because there is no unresolved reference to
__pthread_unwind at the point when libpthread.a is included.  You
could try adding:

   -Wl,--undefined=__pthread_unwind

to the GCC command line before the -lpthread, as a workaround for the
problem.

Presumably the pthread_exit() code should contain an undefined
reference to __pthread_unwind, so I would suggest that you investigate
how this function was compiled and what has happened to this
reference.

Cheers
        Nick