g_once_init*() (Re: Performance implications of GRegex structure)

[Tim Janik <timj gtk org>]

On Sat, 17 Mar 2007, Owen Taylor wrote:

> On Sat, 2007-03-17 at 16:14 +0100, Marco Barisione wrote:

> > Owen: what should do exactly G_STATIC_REGEX_INIT?
>
> I was imagining:
>
> struct _GStaticRegex {
>    GOnce once;
>    GStaticRegex *regex;
>    const gchar *pattern;
>    GRegexCompileFlags flags;
> }
>
> #define G_STATIC_REGEX_INIT(pattern, flags) { \
>    G_ONCE_INIT,                              \
>    NULL,                                     \
>    pattern,                                  \
>    flags                                     \
> }

hm, i'd like to point out that there really should not be
extra macro magic around for handling cross-thread regexps.
with GOnce, GLib provides means for thread-safe one time
initialization already, and if the use of that is too cumbersome,
we're currently working on a more convenient alternative here:
	http://bugzilla.gnome.org/show_bug.cgi?id=65041
with that, you should be able to write:
  static GRegexp *pattern = NULL;
  static gsize initialized = 0;
  if (g_once_init_enter (&initialized))
    {
      pattern = g_regexp_new (...);
      g_once_init_leave (&initialized, 1);
    }
providing a g_once_*() convenience API that can be used everywhere
is a much better way than to re-invent G_STATIC_*() magic for every
component that's potentially used across multiple threads.

> 						- Owen

---
ciaoTJ