Do not write g_pch.cpp if it's already up-to-date

This eliminates rebuilding of main executable by MSVC on every project generation by CMake
This commit is contained in:
alexey.lysiuk 2018-04-19 10:16:04 +03:00
parent 3212da8fcf
commit 220d923e65

View file

@ -14,8 +14,19 @@ function(enable_precompiled_headers PRECOMPILED_HEADER SOURCE_VARIABLE_NAME)
get_filename_component(pch_basename ${PRECOMPILED_HEADER} NAME_WE)
set(pch_abs ${CMAKE_CURRENT_SOURCE_DIR}/${PRECOMPILED_HEADER})
set(pch_unity ${CMAKE_CURRENT_BINARY_DIR}/${pch_basename}.cpp)
FILE(WRITE ${pch_unity} "// Precompiled header unity generated by CMake\n")
FILE(APPEND ${pch_unity} "#include <${pch_abs}>\n")
set(pch_content "// Precompiled header unity generated by CMake\n#include <${pch_abs}>\n")
# Read .cpp if exists
if(EXISTS ${pch_unity})
file(READ ${pch_unity} pch_content_prev)
endif()
# Compare existing .cpp content with the actual one
if (pch_content_prev AND pch_content STREQUAL pch_content_prev)
unset(pch_content)
endif()
# Write .cpp if it's out-of-date
if (pch_content)
FILE(WRITE ${pch_unity} "${pch_content}")
endif()
set_source_files_properties(${pch_unity} PROPERTIES COMPILE_FLAGS "/Yc\"${pch_abs}\"")
# Update properties of source files to use the precompiled header.