[CMake] check_function_exists frailty

[Jack Poulson]

On Wed, Jan 19, 2011 at 3:27 AM, Eric Noulard <eric.noulard at gmail.com>wrote:

> 2011/1/19 Jack Poulson <jack.poulson at gmail.com>:
> > I have no idea why this would occur, but with CMake 2.8.2 on x86_64 I'm
> > getting strange behavior with check_function_exists. Namely, if I perform
> > the sequence
> > set(CMAKE_REQUIRED_LIBRARIES ${MATH_LIBS})
> > check_function_exists(daxpy HAVE_DAXPY)
> > whether or not /usr/lib/libpthread.a or /usr/lib/libpthread.so is in the
> > list changes the answer, even though daxpy is defined in a completely
> > different library!
> > Output with libpthread.so:
> > --
> >
> MATH_LIBS=/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_scalapack_lp64.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_blacs_lp64.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_intel_lp64.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_intel_thread.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_core.a;/opt/intel/Compiler/11.1/072/lib/intel64/libguide.a;/opt/intel/Compiler/11.1/072/lib/intel64/libiomp5.a;/usr/lib/libpthread.so
> > -- Looking for daxpy
> > -- Looking for daxpy - found
> > Output with libpthread.a:
> > --
> >
> MATH_LIBS=/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_scalapack_lp64.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_blacs_lp64.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_intel_lp64.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_intel_thread.a;/opt/intel/Compiler/11.1/072/mkl/lib/em64t/libmkl_core.a;/opt/intel/Compiler/11.1/072/lib/intel64/libguide.a;/opt/intel/Compiler/11.1/072/lib/intel64/libiomp5.a;/usr/lib/libpthread.a
> > -- Looking for daxpy
> > -- Looking for daxpy - not found
> >
> > Any ideas what would be causing this strange behavior? And while I'm on
> the
> > subject, should check_function_exist work with dynamic libraries? I had
> to
> > give up some portability and force find_library to search for the static
> MKL
> > libraries just to get the libpthread.so case to work.
> > I apologize in advance if I've missed something obvious...
>
> May be you have an implicit dependency on dynamic pthread somewhere.
> Are you using icc or gcc ?
>
>
I was using icc for C++ for the project, but it appears
check_function_exists was defaulting to gcc for the C compilation.

As far as I remember check_function_exists is using try_compile.
> May be you can try to run CMake with
>
> --debug-trycompile and look into files
>
> I don't remember where they are... but I'm sure someone will tell you that.
>
>
I used your suggestion of --debug-trycompile and found that there was an
undefined reference for _dl_stack_flags in libpthread.a. The output of
check_function_exists was fairly misleading in this case...perhaps it should
output just 'found' or 'not found'.

Thank you for the help!

Jack
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