Check if a C function can be linked

check_function_exists(<function> <variable>)

Checks that the <function> is provided by libraries on the system and store the result in a <variable>, which 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:


String of additional flags to pass to the compiler. The string must be space-delimited--a ;-list will not work. The contents of CMAKE_<LANG>_FLAGS and its associated configuration-specific variable are automatically added to the compiler command before the contents of CMAKE_REQUIRED_FLAGS.


A ;-list of compiler definitions of the form -DFOO or -DFOO=bar. A definition for the name specified by <resultVar> will also be added automatically.


A ;-list of header search paths to pass to the compiler. These will be the only header search paths used--the contents of the INCLUDE_DIRECTORIES directory property will be ignored.


New in version 3.14.

A ;-list of options to add to the link command (see try_compile() for further details).


A ;-list of libraries to add to the link command. These can be the name of system libraries or they can be Imported Targets (see try_compile() for further details).


New in version 3.1.

If this variable evaluates to a boolean true value, all status messages associated with the check will be suppressed.


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.