CMake - remove a compile flag for a single translation unit

Question

I would like to remove a set compile flag for a single translation unit. Is there a way to do this? (e.g. using set_property?)

Note: the compile-flag ha

Answer 1

A (non-scalable & non-portable) solution is creating a custom command with modified flags. A minimal example that I got working is the following:

cmake_minimum_required(VERSION 2.8)

project(test)
# Some flags
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O2 -Wall")
# Remove unwanted flag
string(REPLACE "-Wall" "" CUSTOM_FLAGS ${CMAKE_CXX_FLAGS})
# Split the flags into a cmake list (; separated)
separate_arguments(CUSTOM_FLAGS UNIX_COMMAND ${CUSTOM_FLAGS})
# Custom command to build your one file.
add_custom_command(
    OUTPUT out.o
    COMMAND ${CMAKE_CXX_COMPILER} 
    ARGS ${CUSTOM_FLAGS} -c ${CMAKE_SOURCE_DIR}/out.cpp 
                         -o ${CMAKE_BINARY_DIR}/out.o
    MAIN_DEPENDENCY out.cpp)

add_executable(test test.cpp out.o)

While far from perfect, it does work which is what counts. The separate_arguments was necessary because otherwise all spaces in CUSTOM_FLAGS were escaped (don't know how to solve that one quickly).