CMP0232

Added in version 4.6.

MSVC flag /Zc:__cplusplus is passed for C++ targets.

By default, the MSVC compiler always defines the __cplusplus preprocessor macro as 199711L, regardless of the C++ standard selected by its /std: flag. Visual Studio 2017 version 15.7 and above offer the /Zc:__cplusplus flag to make __cplusplus report the value of the selected C++ standard, as other compilers do.

In CMake 4.5 and below, /Zc:__cplusplus is not passed, so sources that check __cplusplus see 199711L unless the project adds the flag itself. CMake 4.6 and above prefer to always pass /Zc:__cplusplus when compiling C++ sources with a MSVC compiler that supports it. This policy provides compatibility for projects that have not been updated to expect the behavior.

The OLD behavior for this policy does not add /Zc:__cplusplus. The NEW behavior adds /Zc:__cplusplus when compiling the C++ sources of a target with the MSVC compiler from Visual Studio 2017 version 15.7 or above. The flag is not part of CMAKE_CXX_FLAGS, so it is passed regardless of that variable's value. It is placed before the target's COMPILE_OPTIONS, so a target that needs the original value of the macro under the NEW behavior may add /Zc:__cplusplus- to its compile options.

The policy setting is recorded by each target when it is created. It is also propagated to the test projects of the try_compile() and try_run() commands.

This policy has no effect on other languages, on compilers whose id is not MSVC, or on versions of it that do not support the flag.

This policy was introduced in CMake version 4.6. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

Note

The OLD behavior of a policy is deprecated by definition and may be removed in a future version of CMake.