precompiled_headers.cmake

#
# Christoph Heindl 2010
# Precompiled Headers Demo
# http://cheind.wordpress.com
#

# Instructs the MSVC toolset to use the precompiled header PRECOMPILED_HEADER
# for each source file given in the collection named by SOURCE_VARIABLE_NAME.
function(enable_precompiled_headers_msvc PRECOMPILED_HEADER SOURCE_VARIABLE_NAME)

	if(WITH_HEADER_PRECOMP)
		if(MSVC_IDE)

			set(files ${${SOURCE_VARIABLE_NAME}})

			# Generate precompiled header translation unit
			get_filename_component(pch_basename ${PRECOMPILED_HEADER} NAME_WE)
			set(pch_abs ${PRECOMPILED_HEADER})
			set(pch_unity ${pch_basename}.cpp)
			FILE(WRITE ${pch_unity} "// Precompiled header unity generated by CMake\n")
			FILE(APPEND ${pch_unity} "#include <${pch_abs}>\n")
			set_source_files_properties(${pch_unity}  PROPERTIES COMPILE_FLAGS "/Yc\"${pch_abs}\"")

			# Update properties of source files to use the precompiled header.
			# Additionally, force the inclusion of the precompiled header at beginning of each source file.
			foreach(source_file ${files} )
			set_source_files_properties(
			${source_file} 
			PROPERTIES COMPILE_FLAGS
			"/Yu\"${pch_abs}\" /FI\"${pch_abs}\""
			)
			endforeach(source_file)

			# Finally, update the source file collection to contain the precompiled header translation unit
			set(${SOURCE_VARIABLE_NAME} ${${SOURCE_VARIABLE_NAME}} ${pch_unity} PARENT_SCOPE)
		endif(MSVC_IDE)
	endif(WITH_HEADER_PRECOMP)

endfunction(enable_precompiled_headers_msvc)


function(enable_precompiled_headers_GCC PRECOMPILED_HEADER TARGET_NAME EXTRA_CXX_FLAGS)
	if(WITH_HEADER_PRECOMP)
#ne marche pas avec Clang
#		if("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
#		  SET(EXT_HP pth)
#		  SET(OPTION_HP "-ccl -emit-pth")
#		endif()
		if(CMAKE_COMPILER_IS_GNUCXX)
		  #Message("Gcc")
		  SET(EXT_HP gch)
		  SET(OPTION_HP "-x c++-header")
		endif()

#		IF(CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
		IF(CMAKE_COMPILER_IS_GNUCXX)
			GET_FILENAME_COMPONENT(_name ${PRECOMPILED_HEADER} NAME)

			#SET(_source "${CMAKE_CURRENT_SOURCE_DIR}/${PRECOMPILED_HEADER}")
			SET(_source "${PROJECT_SOURCE_DIR}/include/${PRECOMPILED_HEADER}")

			#SET(_outdir "${CMAKE_CURRENT_SOURCE_DIR}/${_name}.${EXT_HP}")
			SET(_outdir "${PROJECT_SOURCE_DIR}/include/${_name}.${EXT_HP}")
			MAKE_DIRECTORY(${_outdir})
			SET(_output "${_outdir}/.c++")

			STRING(TOUPPER "CMAKE_CXX_FLAGS_${CMAKE_BUILD_TYPE}" _flags_var_name)
                        SET(_compiler_FLAGS ${${_flags_var_name}} ${EXTRA_CXX_FLAGS})

			GET_DIRECTORY_PROPERTY(_directory_flags INCLUDE_DIRECTORIES)
			FOREACH(item ${_directory_flags})
			LIST(APPEND _compiler_FLAGS "-I${item}")
			ENDFOREACH(item)

			GET_DIRECTORY_PROPERTY(_directory_flags DEFINITIONS)
			LIST(APPEND _compiler_FLAGS ${_directory_flags})

			SEPARATE_ARGUMENTS(_compiler_FLAGS)
			#MESSAGE("${CMAKE_CXX_COMPILER} ${_compiler_FLAGS} ${OPTION_HP} -o ${_output} ${_source}")
			ADD_CUSTOM_COMMAND(
				OUTPUT ${_output}				
                                COMMAND ${CMAKE_CXX_COMPILER} ${_compiler_FLAGS} -x c++-header -o ${_output} ${_source}
				DEPENDS ${_source} IMPLICIT_DEPENDS CXX ${_source})
				ADD_CUSTOM_TARGET(${TARGET_NAME}_${EXT_HP} DEPENDS ${_output})

			ADD_DEPENDENCIES(${TARGET_NAME} ${TARGET_NAME}_${EXT_HP})
			SET_TARGET_PROPERTIES(${TARGET_NAME}_${EXT_HP} PROPERTIES COMPILE_FLAGS "-include ${_name} -Winvalid-pch")
		ENDIF(CMAKE_COMPILER_IS_GNUCXX)
		#endif()
	endif(WITH_HEADER_PRECOMP)
endfunction(enable_precompiled_headers_GCC)