Node:Generic Headers, Previous:Particular Headers, Up:Header Files

Generic Header Checks

These macros are used to find system header files not covered by the "particular" test macros. If you need to check the contents of a header as well as find out whether it is present, you have to write your own test for it (see Writing Tests).

AC_CHECK_HEADER (header-file, [action-if-found], [action-if-not-found], [includes = default-includes])

Macro

If the system header file header-file is usable, execute shell commands action-if-found, otherwise execute action-if-not-found. If you just want to define a symbol if the header file is available, consider using AC_CHECK_HEADERS instead. The meaning of "usable" depends upon the content of includes: if includes is empty check whether header-file can be preprocessed without error. if include is set Check whether includes #include <header-file> can be compiled without error. You may use AC_CHECK_HEADER (and AC_CHECK_HEADERS) to check whether two headers are compatible. You may pass any kind of dummy content for includes, such as a single space, a comment, to check whether header-file compiles with success.

AC_CHECK_HEADERS (header-file..., [action-if-found], [action-if-not-found], [includes = default-includes])

Macro

For each given system header file header-file in the whitespace-separated argument list that exists, define HAVE_header-file (in all capitals). If action-if-found is given, it is additional shell code to execute when one of the header files is found. You can give it a value of break to break out of the loop on the first match. If action-if-not-found is given, it is executed when one of the header files is not found. Be sure to read the documentation of AC_CHECK_HEADER to understand the influence of includes.