gpt-undefines (8) - Linux Manuals

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


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


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 excluded.


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:


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:



Michael Bletzinger <> and Eric Blau <>


autoconf(1) autoheader(1)