Cmake fails missing pthread.h - cmake

Question

There was once a bug related to cmake and pthread but it is now fixed.
I use cmake version 3.5.1 on Mac OS. It compiled previously but in the meantime I installed, changed, or updated things. I don't have much knowledge about cmake. The cmake file was written by someone else.
This is the error message I get:
-- Looking for pthread.h
-- Looking for pthread.h - not found
CMake Error at /usr/local/Cellar/cmake/3.5.1/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:148 (message):
Could NOT find Threads (missing: Threads_FOUND)
Call Stack (most recent call first):
/usr/local/Cellar/cmake/3.5.1/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:388 (_FPHSA_FAILURE_MESSAGE)
/usr/local/Cellar/cmake/3.5.1/share/cmake/Modules/FindThreads.cmake:223 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
external/glfw-3.0.3/CMakeLists.txt:74 (find_package)
My cmake file (if relevant).
_minimum_required(VERSION 2.8 FATAL_ERROR)
cmake_policy(VERSION 2.8)
set(FENSTERCHEN fensterchen)
set(FRAMEWORK_NAME framework)
project(${FENSTERCHEN})
if(CMAKE_CURRENT_SOURCE_DIR EQUAL CMAKE_CURRENT_BINARY_DIR)
message(FATAL_ERROR "Source and binary directories must be different")
endif(CMAKE_CURRENT_SOURCE_DIR EQUAL CMAKE_CURRENT_BINARY_DIR)
if(MSVC)
set(BINARY_DIRECTORY build)
endif()
if(("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang") OR ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU") OR (("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Intel") AND UNIX))
set(CMAKE_XCODE_ATTRIBUTE_CLANG_CXX_LANGUAGE_STANDARD "c++0x")
set(CMAKE_XCODE_ATTRIBUTE_CLANG_CXX_LIBRARY "libc++")
set(CMAKE_CXX_FLAGS "-std=c++0x -fopenmp")
set(CMAKE_C_FLAGS "-fopenmp")
endif()
set(CMAKE_CXX_FLAGS "-std=c++0x -fopenmp")
set(CMAKE_C_FLAGS "-fopenmp")
option(FENSTERCHEN_IN_SOURCE_BUILD "FENSTERCHEN_IN_SOURCE_BUILD" OFF)
if(FENSTERCHEN_IN_SOURCE_BUILD)
add_definitions(-DFENSTERCHEN_SOURCE_DIR="${CMAKE_CURRENT_SOURCE_DIR}")
add_definitions(-DFENSTERCHEN_BINARY_DIR="../")
else()
add_definitions(-DFENSTERCHEN_SOURCE_DIR="${CMAKE_CURRENT_SOURCE_DIR}")
add_definitions(-DFENSTERCHEN_BINARY_DIR="${CMAKE_CURRENT_BINARY_DIR}")
endif()
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/external)
add_definitions(-DGLEW_STATIC)
set(GLFW_DIRECTORY glfw-3.0.3)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/external/${GLFW_DIRECTORY}/include)
set(GLFW_INSTALL OFF CACHE STRING "" FORCE)
set(GLFW_BUILD_EXAMPLES OFF CACHE STRING "" FORCE)
set(GLFW_BUILD_TESTS OFF CACHE STRING "" FORCE)
add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/external/${GLFW_DIRECTORY})
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/external/${GLFW_DIRECTORY}/include)
set(GLM_DIRECTORY glm-0.9.5.3)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/external/${GLM_DIRECTORY})
################################
# Add libraries to executables
set(BINARY_FILES glfw ${GLFW_LIBRARIES} ${FREEIMAGE_LIBRARY})
################################
# Add output directory
if(MSVC)
set(EXECUTABLE_OUTPUT_PATH ${CMAKE_CURRENT_BINARY_DIR}/build/)
if(CMAKE_BUILD_TYPE STREQUAL "Debug")
set(COPY_OUTPUT_PATH ${CMAKE_CURRENT_BINARY_DIR}/build/Debug/ )
else(CMAKE_BUILD_TYPE STREQUAL "Debug")
set(COPY_OUTPUT_PATH ${CMAKE_CURRENT_BINARY_DIR}/build/Release/ )
endif(CMAKE_BUILD_TYPE STREQUAL "Debug")
else(MSVC)
if(CMAKE_BUILD_TYPE STREQUAL "Debug")
set(EXECUTABLE_OUTPUT_PATH ${CMAKE_CURRENT_BINARY_DIR}/build/Debug )
else(CMAKE_BUILD_TYPE STREQUAL "Debug")
set(EXECUTABLE_OUTPUT_PATH ${CMAKE_CURRENT_BINARY_DIR}/build/Release )
endif(CMAKE_BUILD_TYPE STREQUAL "Debug")
endif(MSVC)
option(FENSTERCHEN_AUTOMATED_TESTS "FENSTERCHEN_AUTOMATED_TESTS" OFF)
if(FENSTERCHEN_AUTOMATED_TESTS)
add_definitions(-DAUTOMATED_TESTS)
endif()
if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
if (NOT APPLE)
add_definitions(-fpermissive)
endif()
endif()
if(MSVC)
add_definitions(-D_CRT_SECURE_NO_WARNINGS)
endif(MSVC)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/framework)
add_subdirectory(framework)
add_subdirectory(source)
set (FENSTERCHEN_TESTS "false" CACHE BOOL "Set to enable testing.")
if (FENSTERCHEN_TESTS)
set(UNITTEST_PP_DIRECTORY unittest-cpp)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/external/${UNITTEST_PP_DIRECTORY}/UnitTest++)
add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/external/${UNITTEST_PP_DIRECTORY})
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/external/${UNITTEST_PP_DIRECTORY}/UnitTest++)
#set(BINARY_FILES UnitTest++ glfw ${GLFW_LIBRARIES} ${FREEIMAGE_LIBRARY})
add_subdirectory(tests)
enable_testing()
add_test( NAME testFensterchen COMMAND runTests )
endif (FENSTERCHEN_TESTS)
install (DIRECTORY data DESTINATION .)
# See http://www.vtk.org/Wiki/CMake:CPackPackageGenerators
set (CPACK_PACKAGE_VERSION_MAJOR "4")
set (CPACK_PACKAGE_VERSION_MINOR "4")
set (CPACK_PACKAGE_VERSION_PATCH "2")
# Use current date in YYYYMMDD format as patch number
# cpack mistakenly detects Mingw-w64 as win32
if (MINGW)
if (CMAKE_SIZEOF_VOID_P EQUAL 8)
set (CPACK_SYSTEM_NAME win64)
endif ()
endif ()
if (WIN32)
set (CPACK_GENERATOR "ZIP")
else ()
set (CPACK_GENERATOR "TBZ2")
endif ()
include(CPack)
How do I fix this?

Answer 1

Thanks to #Tsyvarev.
The problem was that the "-fopenmp" flag was causing an error because the compiler was set to clang.
From the CMakeFiles/CMakeError.log
clang: error: unsupported option '-fopenmp'
Changing the C++ compiler to g++ and removing the flag from the c compiler solved the problem.