# CheckFunctionExists

Check if a C function can be linked:

    check_function_exists(<function> <variable>)

Check that the `<function>` is provided by libraries on the system and store the result in a `<variable>`. `<variable>` will be created as an internal cache variable.

The following variables may be set before calling this macro to modify the way the check is run:

    CMAKE_REQUIRED_FLAGS = string of compile command line flags
    CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
    CMAKE_REQUIRED_INCLUDES = list of include directories
    CMAKE_REQUIRED_LIBRARIES = list of libraries to link
    CMAKE_REQUIRED_QUIET = execute quietly without messages

Note

Prefer using `CheckSymbolExists` instead of this module, for the following reasons:

- `check_function_exists()` can’t detect functions that are inlined in headers or specified as a macro.
- `check_function_exists()` can’t detect anything in the 32-bit versions of the Win32 API, because of a mismatch in calling conventions.
- `check_function_exists()` only verifies linking, it does not verify that the function is declared in system headers.