the header situation in glib is a little bit random at the moment.

the main problem is that just about everything does #include <glib.h> which means that a single change to a completely-unrelated header file results in the entirety of glib being rebuilt.

i propose that all .c files in glib/ be changed to this:


(for file gfoo.c)

-----
/* Copyright etc...
 *
 */

#include "config.h"                 /* [1] */

#include "gfoo.h"                   /* [2] */

#include <glib/gtestutils.h>        /* [3] */
#include <glib/gslist.h>

#include <stdio.h>                  /* [4] */
#include <string.h>

#include "galias.h"                 /* [5] */

... stuff ...
-----


[1] config.h needs to be in every file and it needs to come first.  See bug 71704.

[2] each .c file should include its corresponding .h before any other includes as a way of 'taking responsibility' for ensuring that the .h file can be #included from any context without errors (ie: the .h file does not require other .h files to come before it).  note that config.h still needs to be first incase the "gfoo.h" includes some system header files.

[3] next, the glib .h files that this module depends on.  it seems to me that this list should be kept as small as possible via transitive reduction (eg: we shouldn't include gmessages.h since that's already included via our include of gtestutils.h).  this increases the chances of changes to .h files breaking things (which will be promptly noticed and fixed) and reduces the chances of .c files silently depending on unnecessary .h files when such changes occur.

<glib.h> should never be included from anything inside of glib/ ever.  test cases should use <glib.h>.  gobject/ and gio/ can use it too.

[4] system headers.  boring.

[5] aliasing stuff.  needs to come after all glib headers, but could maybe be before system headers.


feedback?