CMake could not find OpenMP on macOS

Question

On macOS, CMake cannot find OpenMP, although I've installed OpenMP via Homebrew with
 

brew install libomp

More precisely, when trying to build openCARP, the CMake configuration command

cmake -S. -B_build

gives the following error:

[...]

CMake Error at /opt/homebrew/Cellar/cmake/3.31.2/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:233 (message):

  Could NOT find OpenMP_C (missing: OpenMP_C_FLAGS OpenMP_C_LIB_NAMES)

Call Stack (most recent call first):

  /opt/homebrew/Cellar/cmake/3.31.2/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:603 (_FPHSA_FAILURE_MESSAGE)

  /opt/homebrew/Cellar/cmake/3.31.2/share/cmake/Modules/FindOpenMP.cmake:616 (find_package_handle_standard_args)

  CMakeLists.txt:222 (find_package)

Answer 1

If libomp has been installed via homebrew, this can be solved by exporting the following environment variable:

export OpenMP_ROOT=$(brew --prefix)/opt/libomp

Comments

In addition, if openCARP is built with external tools, and meshtool in particular, setting the following environment variables can also help:

export CPATH=$CPATH:$(brew --prefix)/opt/libomp/include
export LIBRARY_PATH=$LIBRARY_PATH:$(brew --prefix)/opt/libomp/lib