CMAKE_<LANG>_STANDARD_LATEST¶
New 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()