CMake generator expression, differentiate C / C++ code

Question

I would like to add -std=c++11 to my

add_compile_options(\"-std=c++11\")

However, this also adds them to compilation of C

Answer 1

You can use LINKER_LANGUAGE target property to add flag only to C++ targets*:

add_compile_options(
    "$<$,CXX>:-std=c++11>"
)

_{*Note that this will not work for targets with mixed C/C++ sources}

CMAKE_CXX_FLAGS should work fine too:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

Probably you need to add them to cache if it set before project command (e.g. in toolchain):

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11" CACHE STRING "" FORCE)