FindOpenMP: Fails to find OpenMP because of -Werror
To reproduce:
CMakeLists.txt:
set(CMAKE_CXX_FLAGS "-Wall -Wno-unused-parameter -Werror") find_package(OpenMP)
Run from command line:
mkdir build cd build CC=clang-5.0 CXX=clang++-5.0 cmake ../
Gives error:
-- Could NOT find OpenMP_CXX (missing: OpenMP_CXX_FLAGS OpenMP_CXX_LIB_NAMES)
I added some extra debug output to Modules/FindOpenMP.cmake to print out 'OpenMP_TRY_COMPILE_OUTPUT'
Change Dir: /home/mcphail/build/CMakeFiles/CMakeTmp ... /home/mcphail/build/CMakeFiles/FindOpenMP/OpenMPTryFlag.cpp:5:7: error: unused variable 'n' [-Werror,-Wunused-variable] int n = omp_get_max_threads();
For testing I used:
- cmake version 3.12.20180618-gb0b99d
- Clang 5.0
- Ubuntu Xenial
Related to issue #17307 (closed).