[CMake] CMake misidentifies xlc++ as Clang

[Robert Maynard]

Hi.

1. You can report this issue on the CMake gitlab (
https://gitlab.kitware.com/cmake/cmake/issues ). You will want to
attach the result of dumping all defines from the compiler ( xlc++ -dD
-E - < /dev/null  or xlc++ -dM -E ).  Currently it looks like we are
using '__IBMCPP__' to detect xlc++, and that might not be defined on
the power pc platform.

2. If my guess about about 1 is correct, You can try setting the
environment variable CXX_FLAGS to -qxlcompatmacros and see if that
works ( https://www.ibm.com/support/knowledgecenter/SSXVZZ_13.1.3/com.ibm.xlcpp1313.lelinux.doc/compiler_ref/xlmacros.html#xlmacros__suplink1
)

On Wed, Mar 7, 2018 at 4:22 PM, Thompson, KT <kgt at lanl.gov> wrote:
> Hi,
>
>
>
> I am using cmake-3.9.4 on a power9 system with CXX=xlc++ (IBM XL C++) and
> CMake is misidentifying the compiler as "clang".
>
>
>
> % uname -a
>
> Linux cn2021 4.11.0-44.4.1.el7a.ppc64le #1 SMP Sat Dec 9 02:17:51 EST 2017
> ppc64le ppc64le ppc64le GNU/Linux
>
>
>
> % echo $CXX
>
> xlc++
>
>
>
> % $CXX --version
>
> IBM XL C/C++ for Linux, V13.1.6 (Community Edition)
>
> Version: 13.01.0006.0001
>
>
>
> % cmake ..
>
> -- The CXX compiler identification is Clang 4.0.1
>
> -- Check for working CXX compiler:
> /projects/opt/ppc64le/ibm/xlc-13.1.6/xlC/13.1.6/bin/xlc++
>
> -- Check for working CXX compiler:
> /projects/opt/ppc64le/ibm/xlc-13.1.6/xlC/13.1.6/bin/xlc++ -- works
>
> …
>
>
>
> Because, the compiler_ID is misidentified, inappropriate compiler options
> are added when CXX_CXX_STANDARD is set (along with other issues).
>
>
>
> Question 1: How do I report this as a bug? What additional information is
> needed to characterize the failure mode?
>
>
>
> Question 2: Is there a way to force the compiler ID to be "XL" as a
> temporary work around until the bug is fixed?
>
>
>
> Thank you,
>
>
>
> -kt
>
>
>
>
> --
>
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