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       gpt-undefines - Generate a list of preprocessor macros that are not


       gpt-undefines [-srcdir=PATH -config -disable-undefs -verbose -help]
       headers containing defines


       gpt-undefines Generates a list of preprocessor macros that are not
       defined internally in the source code.  Macros that are defined in the
       header files listed during gpt-undefines’s invocation will also be


           Use PATH as the directory containing the source code.  Source code
           in the entire directory tree will be scanned. Default PATH is the
           directory gpt-undefines was invoked in.

           Prints the list out in a format that can be pasted into an
           installable header file.

           Do not count commented out undefines as a define. This technique is
           used by autoconf to indicate a negative test result.  Example:

              /* #undef HAVE_TCP_FASTACK */

Managing Autoconf defines.

       By default the defines tested for by the configure script are stored in
       a file called config.h.  This file should never be installed. to add
       autoconf defines to config.h simply add the define in the following
       format to the file acconfig.h:

          #undef AUTOCONF_DEFINE

       acconfig.h is tranformed into a by the script autoheader.
       Then the configure script transform it into config.h.

       A problem occurs when the autoconf defines are used in installed header
       files.  In this case the defines should be put in an installable header
       file using the following format:

          #ifndef AUTOCONF_DEFINE
          #undef AUTOCONF_DEFINE


       autoconf(1) autoheader(1)


       Michael Bletzinger <> and Eric Blau