New in version 3.20.
Source file extensions must be explicit.
In CMake 3.19 and below, if a source file could not be found by the name specified, it would append a list of known extensions to the name to see if the file with the extension could be found. For example, this would allow the user to run:
main.c in the executable without specifying the extension.
Starting in CMake 3.20, CMake prefers all source files to have their extensions explicitly listed:
OLD behavior for this policy is to implicitly append known extensions
to source files if they can't be found. The
NEW behavior of this policy is
to not append known extensions and require them to be explicit.
This policy was introduced in CMake version 3.20. CMake version 3.28.20231129-g348cdb5
warns when the policy is not set and uses
OLD behavior. Use the
cmake_policy() command to set it to
OLD behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.