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(autoconf.info)Autoheader Macros

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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 Note: Defining
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 the 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.