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Re: GCC 4.7.0 and C++ atomics


On 03/07/2012 12:44 PM, Andrew MacLeod wrote:
On 03/07/2012 10:11 AM, Sebastian Huber wrote:
Hello,

I run the GCC testsuite for GCC 4.7.0 20120307

http://gcc.gnu.org/ml/gcc-testresults/2012-03/msg00782.html

I got a lot of errors like this:

FAIL: g++.dg/simulate-thread/atomics-1.C  -O0 -g  (test for excess
errors)
148796 Excess errors:
148797
/home/sh/rtems-testing/gcc/b-arm-gcc/arm-rtemseabi4.11/libstdc++-v3/include/bits/atomic_base.h:458:
undefined reference to `__sync_synchronize'
148798
/home/sh/rtems-testing/gcc/b-arm-gcc/arm-rtemseabi4.11/libstdc++-v3/include/bits/atomic_base.h:458:
undefined reference to `__sync_synchronize'
148799
/home/sh/rtems-testing/gcc/b-arm-gcc/arm-rtemseabi4.11/libstdc++-v3/include/bits/atomic_base.h:458:
undefined reference to `__sync_synchronize'
148800
/home/sh/rtems-testing/gcc/b-arm-gcc/arm-rtemseabi4.11/libstdc++-v3/include/bits/atomic_base.h:458:
undefined reference to `__sync_synchronize'
148801
/home/sh/rtems-testing/gcc/b-arm-gcc/arm-rtemseabi4.11/libstdc++-v3/include/bits/atomic_base.h:438:
undefined reference to `__sync_synchronize'
148802
/tmp/ccgSyPe7.o:/home/sh/rtems-testing/gcc/b-arm-gcc/arm-rtemseabi4.11/libstdc++-v3/include/bits/atomic_base.h:438:
more undefined references to `__sync_synchronize' follow

Who is supposed to provide this function? expand_mem_thread_fence

Looks like it is defaulting to emitting the synchronize_libfunc call,
which is suppose to be provided by libgcc I think...

rth, you are familiar with how this part is suppose to hook up properly...

I traced the code in expand_mem_thread_fence, and the sync_synchronize
is being emiited by:

else if (synchronize_libfunc != NULL_RTX)
          emit_library_call (synchronize_libfunc, LCT_NORMAL, VOIDmode, 0);

presumably something just isn't being linked to the executable?  or
maybe not being built into libgcc?
I haven't looked into this specific case but often it is a case of
a multilib variant not being covered by the existing code.
Andrew

Andrew




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