[faldstool]

>And then for CHECK_FUNCTION_EXISTS();, there are a few rare compilers that do not throw an error at compile-time if said function does not exist. check_function_exists() verifies that the symbol can be linked to rather than compile. That's why it gives it a bogus declaration of char CHECK_FUNCTION_EXISTS().

Funny enough I was trying to build a library yesterday that used check_function_exists() to detect the presence of some library functions. The project was set up to output a static library so check_function_exists() returned true for all the missing functions since it linked the test program without issue. https://gitlab.kitware.com/cmake/cmake/-/issues/18121