# CMP0067

Honor language standard in `try_compile()` source-file signature.

The `try_compile()` source file signature is intended to allow callers to check whether they will be able to compile a given source file with the current toolchain. In order to match compiler behavior, any language standard mode should match. However, CMake 3.7 and below did not do this. CMake 3.8 and above prefer to honor the language standard settings for `C`, `CXX` (C++), and `CUDA` using the values of the variables:

- `CMAKE_C_STANDARD`
- `CMAKE_C_STANDARD_REQUIRED`
- `CMAKE_C_EXTENSIONS`
- `CMAKE_CXX_STANDARD`
- `CMAKE_CXX_STANDARD_REQUIRED`
- `CMAKE_CXX_EXTENSIONS`
- `CMAKE_CUDA_STANDARD`
- `CMAKE_CUDA_STANDARD_REQUIRED`
- `CMAKE_CUDA_EXTENSIONS`

This policy provides compatibility for projects that do not expect the language standard settings to be used automatically.

The `OLD` behavior of this policy is to ignore language standard setting variables when generating the `try_compile` test project. The `NEW` behavior of this policy is to honor language standard setting variables.

This policy was introduced in CMake version 3.8. Unlike most policies, CMake version 3.16.0-rc3 does not warn by default when this policy is not set and simply uses `OLD` behavior. See documentation of the `CMAKE_POLICY_WARNING_CMP0067` variable to control the warning.

Note

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