<LANG>_STANDARD_REQUIRED

The variations are:

:prop_tgt:C_STANDARD_REQUIRED
:prop_tgt:CXX_STANDARD_REQUIRED
:prop_tgt:CUDA_STANDARD_REQUIRED
:prop_tgt:HIP_STANDARD_REQUIRED
:prop_tgt:OBJC_STANDARD_REQUIRED
:prop_tgt:OBJCXX_STANDARD_REQUIRED

These properties specify whether the value of :prop_tgt:<LANG>_STANDARD is a requirement. When false or unset, the :prop_tgt:<LANG>_STANDARD target property is treated as optional and may "decay" to a previous standard if the requested standard is not available. When <LANG>_STANDARD_REQUIRED is set to true, :prop_tgt:<LANG>_STANDARD becomes a hard requirement and a fatal error will be issued if that requirement cannot be met.

Note that the actual language standard used may be higher than that specified by :prop_tgt:<LANG>_STANDARD, regardless of the value of <LANG>_STANDARD_REQUIRED. In particular, :ref:usage requirements <Target Usage Requirements> or the use of :manual:compile features <cmake-compile-features(7)> can raise the required language standard above what :prop_tgt:<LANG>_STANDARD specifies.

These properties are initialized by the value of the :variable:CMAKE_<LANG>_STANDARD_REQUIRED variable if it is set when a target is created.

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