ax_define_sub_path
==================

Synopsis
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     AX_DEFINE_SUB_PATH(DEFNAME, varname, description)

Description
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Look at varname and detect the subpath that it contains relative to $prefix/$exec_prefix. If the path is indeed relative to $prefix/$exec_prefix, then a single "./" (dotslash) is prepended, otherwise it can be seen as an absolute path that cannot be moved, which you possibly do for "/etc" files, or even those ending up in "/lib/modules" or "/winnt/system".

This macro is not very intelligent, it's just a first try in this direction. It does currently just look into the current patterns, and replaces a ${prefix} with a simple dot. Amazingly, it works quite well for most packages.

Example (configure.ac):

       AX_DEFINE_DIR([EPREFIX], [exec_prefix], [--exec-prefix or default])
       AX_DEFINE_SUB_PATH([PATH_LIBDIR], [libdir], [--bindir subdir])
       AC_DEFINE_UNQUOTED([PACKAGE],"$PACKAGE", [Name of package])

Example (in C):

       static const char _libdir[] = PATH_LIBDIR; /* configure default */
       char* libdir;
       char* eprefix = getenv (PACKAGE "DIR");
       if (! eprefix) eprefix = EPREFIX; /* default */
       if (*_libdir != '.') libdir = strdup(_libdir);
       else {
          libdir = malloc(strlen(eprefix) + strlen(_libdir) + 2);
          strcpy(libdir, eprefix);
          strcat(libdir, PATH_DELIMITER_STRING);
          strcat(libdir, _libdir);
       }
       ...
       free (libdir);

The AX_DEFINE_SUB_PATHS(varnames) macro looks for the given various install-paths that largely depend on either ${prefix} or ${exec_prefix}. Just cut out the prefix and ac_define the value. The value is uppercased and PATH_ prepended ie. ax_define_sub_paths(bindir libdir pkgdatadir) will create the defines PATH_BINDIR PATH_LIBDIR PATH_PKGDATADIR - see posix' include/paths.h that creates _PATH_DEV and friends.

Source Code
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Download the latest version of ax_define_sub_path.m4 (http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_define_sub_path.m4) or browse the macro's revision history (http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_define_sub_path.m4).

License
*******

Copyright © 2008 Guido U. Draheim guidod@gmx.de

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

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