New in version 3.1.
Boolean describing whether the value of CXX_STANDARD is a requirement.
If this property is set to ON, then the value of the CXX_STANDARD target property is treated as a requirement. If this property is OFF or unset, the CXX_STANDARD target property is treated as optional and may “decay” to a previous standard if the requested is not available. For compilers that have no notion of a standard level, such as MSVC 1800 (Visual Studio 2013) and lower, this has no effect.
See the cmake-compile-features(7) manual for information on compile features and a list of supported compilers.
This property is initialized by the value of the CMAKE_CXX_STANDARD_REQUIRED variable if it is set when a target is created.
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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.19/prop_tgt/CXX_STANDARD_REQUIRED.html