# CheckSourceCompiles

New in version 3.19.

Check if given source compiles and links into an executable.

check_source_compiles

      check_source_compiles(<lang> <code> <resultVar>
                            [FAIL_REGEX <regex1> [<regex2>...]]
                            [SRC_EXT <extension>])

  Check that the source supplied in `<code>` can be compiled as a source file for the requested language and linked as an executable. The result will be stored in the internal cache variable specified by `<resultVar>`, with a boolean true value for success and boolean false for failure. If `FAIL_REGEX` is provided, then failure is determined by checking if anything in the compiler output matches any of the specified regular expressions.

  By default, the test source file will be given a file extension that matches the requested language. The `SRC_EXT` option can be used to override this with `.<extension>` instead.

  The `<code>` must contain a valid main program. For example:

      check_source_compiles(C
      "#include <stdlib.h>
      #include <stdnoreturn.h>
      noreturn void f(){ exit(0); }
      int main(void) { f(); return 1; }"
      HAVE_NORETURN)

      check_source_compiles(Fortran
      "program test
      error stop
      end program"
      HAVE_ERROR_STOP)

  The underlying check is performed by the `try_compile()` command. The compile and link commands can be influenced by setting any of the following variables prior to calling `check_source_compiles()`:

  `CMAKE_REQUIRED_FLAGS`

    Additional flags to pass to the compiler. Note that 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`.

  `CMAKE_REQUIRED_DEFINITIONS`

    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.

  `CMAKE_REQUIRED_INCLUDES`

    A ;-list of header search paths to pass to the compiler. These will be the only header search paths used by `try_compile()`, i.e. the contents of the `INCLUDE_DIRECTORIES` directory property will be ignored.

  `CMAKE_REQUIRED_LINK_OPTIONS`

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

  `CMAKE_REQUIRED_LIBRARIES`

    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).

  `CMAKE_REQUIRED_QUIET`

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

  The check is only performed once, with the result cached in the variable named by `<resultVar>`. Every subsequent CMake run will re-use this cached value rather than performing the check again, even if the `<code>` changes. In order to force the check to be re-evaluated, the variable named by `<resultVar>` must be manually removed from the cache.