4.8.3 Autoheader Macros

autoheader scans `configure.ac' and figures out which C preprocessor symbols it might define. It knows how to generate templates for symbols defined by AC_CHECK_HEADERS, AC_CHECK_FUNCS etc., but if you AC_DEFINE any additional symbol, you must define a template for it. If there are missing templates, autoheader fails with an error message.

The simplest way to create a template for a symbol is to supply the description argument to an `AC_DEFINE(symbol)'; see 7.1 Defining C Preprocessor Symbols. You may also use one of the following macros.

Macro: AH_VERBATIM (key, template)

Tell autoheader to include the template as-is in the header template file. This template is associated with the key, which is used to sort all the different templates and guarantee their uniqueness. It should be a symbol that can be AC_DEFINE'd.

For example:

AH_VERBATIM([_GNU_SOURCE], [/* Enable GNU extensions on systems that have them. */ #ifndef _GNU_SOURCE # define _GNU_SOURCE #endif])

Macro: AH_TEMPLATE (key, description)

Tell autoheader to generate a template for key. This macro generates standard templates just like AC_DEFINE when a description is given.

For example:

AH_TEMPLATE([CRAY_STACKSEG_END], [Define to one of _getb67, GETB67, getb67 for Cray-2 and Cray-YMP systems. This function is required for alloca.c support on those systems.])

will generate the following template, with the description properly justified.

/* Define to one of _getb67, GETB67, getb67 for Cray-2 and Cray-YMP systems. This function is required for alloca.c support on those systems. */ #undef CRAY_STACKSEG_END

Macro: AH_TOP (text)

Include text at the top of the header template file.

Macro: AH_BOTTOM (text)

Include text at the bottom of the header template file.