How to enable C++17 in CMake

Solution 1:

Modern CMake propose an interface for this purpose target_compile_features. Documentation is here: Requiring Language Standards

Use it like this:

target_compile_features(${TARGET_NAME} PRIVATE cxx_std_17)

Solution 2:

Your approach is the correct one, but it will not work for MSVC on versions of CMake prior to 3.10.

From the CMake 3.9 documentation:

For compilers that have no notion of a standard level, such as MSVC, this has no effect.

In short, CMake haven't been updated to accommodate for the standard flags added to VC++ 2017.

You have to detect if VC++ 2017 (or later) is used and add the corresponding flags yourself for now.

In CMake 3.10 (and later) this have been fixed for newer version of VC++. See the 3.10 documentation.

Solution 3:

In modern CMake, I've found it best to assign CXX standards at the target level instead of global variable level and use the built in properties (seen here: https://cmake.org/cmake/help/latest/manual/cmake-properties.7.html) to keep it compiler agnostic.

For Example:

set_target_properties(FooTarget PROPERTIES
            CXX_STANDARD 17
            CXX_EXTENSIONS OFF
            etc..
            )

Solution 4:

You can keep that set(CMAKE_CXX_STANDARD 17) for other compilers, like Clang and GCC. But for Visual Studio, it's useless.

If CMake still doesn't support this, you can do the following for Visual Studio:

if(MSVC)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /std:c++17")
endif(MSVC)

EDIT: As the question title doesn't mention the compiler, let me add that for gcc, clang and similar compilers, this is the command to enable C++17:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")

Solution 5:

when using vs2019

set(CMAKE_CXX_STANDARD 17)