Appending compiler flags to a file with CMake

Question

How do I add a compiler flag (I want to APPEND it, not overwrite the others) to a single translation unit with cmake?

I tried with

set_source_files_properties(MyFile.cpp PROPERTIES CMAKE_CXX_FLAGS "-msse4.1")

but it isn't working.. any advice on how to do that?

Answer 1

For CMake 3.0 or later, use the COMPILE_OPTIONS property to add a flag to a single translation unit, i.e.:

set_property(SOURCE MyFile.cpp APPEND PROPERTY COMPILE_OPTIONS "-msse4.1")

For earlier versions of CMake, use the COMPILE_FLAGS property. COMPILE_FLAGS is a string property. Therefore the correct way to append additional options to it is to use the APPEND_STRING variant of the set_property command:

set_property(SOURCE MyFile.cpp APPEND_STRING PROPERTY COMPILE_FLAGS " -msse4.1 ")