CMAKE_<LANG>_STANDARD_LATEST — CMake 4.0.0 Documentation

# CMAKE_<LANG>_STANDARD_LATEST

Added in version 3.30.

This variable represents the minimum between the latest version of the standard for language `<LANG>` which is supported by the current compiler and the latest version which is supported by CMake. Its value will be set to one of the supported values of the corresponding `<LANG>_STANDARD` target property; see the documentation of that property for a list of supported languages.

See the `cmake-compile-features(7)` manual for information on compile features and a list of supported compilers.

Note

`CMAKE_<LANG>_STANDARD_LATEST` will never be set to a language standard which CMake recognizes but provides no support for. Unless explicitly stated otherwise, every value which is supported by the corresponding `<LANG>_STANDARD` target property represents a standard of language `<LANG>` which is both recognized and supported by CMake.

## Checking for Language Standard Support

It is possible to use the value of the `CMAKE_<LANG>_STANDARD_LATEST` variable to check for language standard support. This can be used to, e.g., conditionally enable optional features for a distributed library.

When doing so, one should be careful to not rely on integer value comparisons between standard levels. This is because some older standards of a given language which are supported by CMake (e.g., C++98, represented as `98`) will have a higher numerical value than newer standards of that same language.

The following code sample demonstrates how one might correctly check for C++17 support:

    # Careful! We cannot do direct integer comparisons with
    # CMAKE_CXX_STANDARD_LATEST because some earlier C++ standards (e.g.,
    # C++98) will have a higher numerical value than our requirement (C++17).
    #
    # Instead, we keep a list of unsupported C++ standards and check if
    # CMAKE_CXX_STANDARD_LATEST appears in that list.
    set(UNSUPPORTED_CXX_STANDARDS
      98
      11
      14
    )

    list(FIND UNSUPPORTED_CXX_STANDARDS ${CMAKE_CXX_STANDARD_LATEST} UNSUPPORTED_CXX_STANDARDS_INDEX)

    if(UNSUPPORTED_CXX_STANDARDS_INDEX EQUAL -1)
      # We know that the current compiler supports at least C++17. Enabling
      # some optional feature...
    else()
      message(STATUS
        "Feature X is disabled because it requires C++17, but the current "
        "compiler only supports C++${CMAKE_CXX_STANDARD_LATEST}."
      )
    endif()