CMake Error: Could NOT find OpenMP_C (missing: OpenMP_C_FLAGS) using clang on Mac OS

Question

I'm trying to get triSYCL to work and for that I need OpenMP. I'm trying to build my project with this CMakeLists file:

cmake_minimum_required(VERSION 3.16.2)
project(acDataFlow)

if (NOT DEFINED AC_DATA_FLOW_ROOT_DIR)
    message(WARNING "AC_DATA_FLOW_ROOT_DIR will be ${CMAKE_CURRENT_LIST_DIR}, if you're not running the CMakeLists.txt in the root dir of the acDataFlow library, please set the variable AC_DATA_FLOW_ROOT_DIR to the path to the root of the acDataFlow library")   #only for Gian Laager, normally the user will set this variable
    set(AC_DATA_FLOW_ROOT_DIR ${CMAKE_CURRENT_LIST_DIR})
endif ()

if (DEFINED GIAN_LAAGERS_MAC)
    set(CMAKE_C_COMPILER "/usr/bin/clang")
    set(CMAKE_CXX_COMPILER "/usr/bin/clang++")
    set(CMAKE_CXX_COMPILER_ID Clang)
    set(CMAKE_C_COMPILER_ID Clang)

    set(OPENMP_LIBRARIES "/usr/local/opt/llvm/lib")
    set(OPENMP_INCLUDES "/usr/local/opt/llvm/include")

    link_directories(${OPENMP_LIBRARIES})
    message(STATUS ${GIAN_LAAGERS_MAC})
endif ()

set(OpenMP_C "${CMAKE_C_COMPILER}")
set(OpenMP_C_FLAGS "-fopenmp=libomp -Wno-unused-command-line-argument")
set(OpenMP_C_LIB_NAMES "libomp" "libgomp" "libiomp5")
set(OpenMP_libomp_LIBRARY ${OpenMP_C_LIB_NAMES})
set(OpenMP_libgomp_LIBRARY ${OpenMP_C_LIB_NAMES})
set(OpenMP_libiomp5_LIBRARY ${OpenMP_C_LIB_NAMES})
set(OpenMP_CXX "${CMAKE_CXX_COMPILER}")
set(OpenMP_CXX_FLAGS "-fopenmp=libomp -Wno-unused-command-line-argument")
set(OpenMP_CXX_LIB_NAMES "libomp" "libgomp" "libiomp5")
set(OpenMP_libomp_LIBRARY ${OpenMP_CXX_LIB_NAMES})
set(OpenMP_libgomp_LIBRARY ${OpenMP_CXX_LIB_NAMES})
set(OpenMP_libiomp5_LIBRARY ${OpenMP_CXX_LIB_NAMES})

#set(CMAKE_COMPILER_IS_GNUCXX "ON")

set(CMAKE_CXX_STANDARD 17)

set(SRC_FILES
        ${AC_DATA_FLOW_ROOT_DIR}/src/acDataFlow.cpp
        )

set(HEADER_FILES
        ${AC_DATA_FLOW_ROOT_DIR}/include/acDataFlow.h
        )

set(Boost_INCLUDE_DIR ${AC_DATA_FLOW_ROOT_DIR}/deps/boost)

include_directories(${AC_DATA_FLOW_ROOT_DIR}/include)

set(TRISYCL_OPENCL "ON")
if (CMAKE_DEBUG)
    set(TRISYCL_DEBUG "ON")
endif ()
set(TRISYCL_INCLUDE_DIR ${AC_DATA_FLOW_ROOT_DIR}/deps/SYCL/include)

include(${AC_DATA_FLOW_ROOT_DIR}/deps/SYCL/CMakeLists.txt)
include_directories(${AC_DATA_FLOW_ROOT_DIR}/deps/SYCL/include)

find_package(OpenCL)
add_library(acDataFlow ${SRC_FILES} ${HEADER_FILES})

This statements if (DEFINED GIAN_LAAGERS_MAC) means that there are options for my machine.

I tried other compilers (cc standard compiler, gcc-8 and gcc-9) but nothing seams to work.

I get this error when I run the project:

CMake Error at /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
  Could NOT find OpenMP_C (missing: OpenMP_C_FLAGS)
Call Stack (most recent call first):
  /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:393 (_FPHSA_FAILURE_MESSAGE)
  /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.16/Modules/FindOpenMP.cmake:511 (find_package_handle_standard_args)
  deps/SYCL/cmake/FindTriSYCL.cmake:214 (find_package)
  deps/SYCL/CMakeLists.txt:13 (include)
  CMakeLists.txt:74 (include)

Does any body has an idea how I can get to run?

Thats the link to the GitHub repository

With out compiler compiler settings (as mentioned from Tsyvarev)

My CMakeLists now looks like this:

cmake_minimum_required(VERSION 3.16.2)

set(ENV{CC} "/usr/bin/clang")
set(ENV{CXX} "/usr/bin/clang++")
set(ENV{LDFLAGS} "-L/usr/local/opt/llvm/lib")
set(ENV{CPPFLAGS} "-I/usr/local/opt/llvm/include")

project(acDataFlow)

find_package(OpenMP REQUIRED)

if (NOT DEFINED AC_DATA_FLOW_ROOT_DIR)
...

and that's the output in the CMakeOutput.log file:

The system is: Darwin - 19.5.0 - x86_64
Compiling the C compiler identification source file "CMakeCCompilerId.c" succeeded.
Compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang 
Build flags: 
Id flags:  

The output was:
0


Compilation of the C compiler identification source "CMakeCCompilerId.c" produced "a.out"

The C compiler identification is AppleClang, found in "/Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/3.16.5/CompilerIdC/a.out"

Compiling the CXX compiler identification source file "CMakeCXXCompilerId.cpp" succeeded.
Compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ 
Build flags: 
Id flags:  

The output was:
0


Compilation of the CXX compiler identification source "CMakeCXXCompilerId.cpp" produced "a.out"

The CXX compiler identification is AppleClang, found in "/Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/3.16.5/CompilerIdCXX/a.out"

Determining if the C compiler works passed with the following output:
Change Dir: /Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_7b008/fast && /Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/cmTC_7b008.dir/build.make CMakeFiles/cmTC_7b008.dir/build
Building C object CMakeFiles/cmTC_7b008.dir/testCCompiler.c.o
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang   -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk   -o CMakeFiles/cmTC_7b008.dir/testCCompiler.c.o   -c /Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/CMakeTmp/testCCompiler.c
Linking C executable cmTC_7b008
/Applications/CLion.app/Contents/bin/cmake/mac/bin/cmake -E cmake_link_script CMakeFiles/cmTC_7b008.dir/link.txt --verbose=1
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang   -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -Wl,-search_paths_first -Wl,-headerpad_max_install_names -L/usr/local/opt/llvm/lib  CMakeFiles/cmTC_7b008.dir/testCCompiler.c.o  -o cmTC_7b008 



Detecting C compiler ABI info compiled with the following output:
Change Dir: /Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_8d2d7/fast && /Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/cmTC_8d2d7.dir/build.make CMakeFiles/cmTC_8d2d7.dir/build
Building C object CMakeFiles/cmTC_8d2d7.dir/CMakeCCompilerABI.c.o
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang   -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk   -v -Wl,-v -o CMakeFiles/cmTC_8d2d7.dir/CMakeCCompilerABI.c.o   -c /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.16/Modules/CMakeCCompilerABI.c
Apple clang version 11.0.3 (clang-1103.0.32.62)
Target: x86_64-apple-darwin19.5.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
clang: warning: -Wl,-v: 'linker' input unused [-Wunused-command-line-argument]
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.15.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name CMakeCCompilerABI.c -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=all -fno-strict-return -masm-verbose -munwind-tables -target-sdk-version=10.15.4 -target-cpu penryn -dwarf-column-info -debugger-tuning=lldb -target-linker-version 556.6 -v -coverage-notes-file /Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/CMakeTmp/CMakeFiles/cmTC_8d2d7.dir/CMakeCCompilerABI.c.gcno -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/11.0.3 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -internal-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/usr/local/include -internal-isystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/11.0.3/include -internal-externc-isystem /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/usr/include -internal-externc-isystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Wno-objc-signed-char-bool-implicit-int-conversion -Wno-extra-semi-stmt -Wno-quoted-include-in-framework-header -fdebug-compilation-dir /Users/gianlaager/Documents/code/C++/ClionProjects/acDataFlow/cmake-build-release/CMakeFiles/CMakeTmp -ferror-limit 19 -fmessage-length 0 -stack-protector 1 -fstack-check -mdarwin-stkchk-strong-link -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fobjc-runtime=macosx-10.15.0 -fmax-type-align=16 -fdiagnostics-show-option -o CMakeFiles/cmTC_8d2d7.dir/CMakeCCompilerABI.c.o -x c /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.16/Modules/CMakeCCompilerABI.c
clang -cc1 version 11.0.3 (clang-1103.0.32.62) default target x86_64-apple-darwin19.5.0
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/usr/local/include"
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/11.0.3/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/usr/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/System/Library/Frameworks (framework directory)
End of search list.
Linking C executable cmTC_8d2d7
/Applications/CLion.app/Contents/bin/cmake/mac/bin/cmake -E cmake_link_script CMakeFiles/cmTC_8d2d7.dir/link.txt --verbose=1
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang   -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -Wl,-search_paths_first -Wl,-headerpad_max_install_names -L/usr/local/opt/llvm/lib -v -Wl,-v CMakeFiles/cmTC_8d2d7.dir/CMakeCCompilerABI.c.o  -o cmTC_8d2d7 
Apple clang version 11.0.3 (clang-1103.0.32.62)
Target: x86_64-apple-darwin19.5.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -lto_library /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libLTO.dylib -dynamic -arch x86_64 -platform_version macos 10.15.0 10.15.4 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -o cmTC_8d2d7 -L/usr/local/opt/llvm/lib -search_paths_first -headerpad_max_install_names -v CMakeFiles/cmTC_8d2d7.dir/CMakeCCompilerABI.c.o -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/11.0.3/lib/darwin/libclang_rt.osx.a
@(#)PROGRAM:ld  PROJECT:ld64-556.6
BUILD 17:57:49 Apr 24 2020
...

hopfuly that's all you need, I can't show the whole file, because it's to big.

Answer 1

I'm Idiot! I don't even have to run CMake on triSYCL because it's a headers only library. I found that on this website in the top of the documentation section

So I can use this CMakeLists.txt file and it works perfectly:

cmake_minimum_required(VERSION 3.16.2)

project(acDataFlow)

set(CMAKE_CXX_STANDARD 17)

if (NOT DEFINED AC_DATA_FLOW_ROOT_DIR)
    message(WARNING "AC_DATA_FLOW_ROOT_DIR will be ${CMAKE_CURRENT_LIST_DIR}, if you're not running the CMakeLists.txt in the root dir of the acDataFlow library, please set the variable AC_DATA_FLOW_ROOT_DIR to the path to the root of the acDataFlow library")   #only for Gian Laager, normally the user will set this variable
    set(AC_DATA_FLOW_ROOT_DIR ${CMAKE_CURRENT_LIST_DIR})
endif ()

set(SRC_FILES
        ${AC_DATA_FLOW_ROOT_DIR}/src/acDataFlow.cpp
        )

set(HEADER_FILES
        ${AC_DATA_FLOW_ROOT_DIR}/include/acDataFlow.h
        )

include_directories(${AC_DATA_FLOW_ROOT_DIR}/include)

set(Boost_INCLUDE_DIR ${AC_DATA_FLOW_ROOT_DIR}/deps/boost)
include_directories(${AC_DATA_FLOW_ROOT_DIR}/deps/boost)

include_directories(${AC_DATA_FLOW_ROOT_DIR}/deps/SYCL/include)

add_library(acDataFlow ${SRC_FILES} ${HEADER_FILES})