CMAKE_<LANG>_STANDARD_LATEST

.. versionadded:: 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 :prop_tgt:<LANG>_STANDARD target property; see the documentation of that property for a list of supported languages.

See the :manual: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 :prop_tgt:<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:

.. code-block:: cmake

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()