# CheckIncludeFiles

Provides a macro to check if a list of one or more header files can be included together.

check_include_files

      check_include_files("<includes>" <variable> [LANGUAGE <language>])

  Check if the given `<includes>` list may be included together in a source file and store the result in an internal cache entry named `<variable>`. Specify the `<includes>` argument as a ;-list of header file names.

  If `LANGUAGE` is set, the specified compiler will be used to perform the check. Acceptable values are `C` and `CXX`. If not set, the C compiler will be used if enabled. If the C compiler is not enabled, the C++ compiler will be used if enabled.

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

> `CMAKE_REQUIRED_FLAGS`

>   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`.

> `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--the contents of the `INCLUDE_DIRECTORIES` directory property will be ignored.

> `CMAKE_REQUIRED_LINK_OPTIONS`

>   Added in version 3.14.

>   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_LINK_DIRECTORIES`

>   Added in version 3.31.

>   A ;-list of libraries search paths to pass to the linker (see `try_compile()` for further details).

> `CMAKE_REQUIRED_QUIET`

>   Added in version 3.1.

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

See modules `CheckIncludeFile` and `CheckIncludeFileCXX` to check for a single header file in `C` or `CXX` languages.