[Geany-devel] [Patch] after g_strndup, use g_free instead of free

[Colomban Wendling]

Le mercredi 19 mai 2010 à 23:10 +0200, Enrico Tröger a écrit :
> On Sun, 16 May 2010 22:40:25 +0200, Colomban wrote:
> > it isn't in general. g_free() frees a memory chunk with the
> > registered free function in the GLib's memory VTable, which by
> > default is libc's free() -- and then g_free() and free() are
> > equivalent. But if for a reason or another the VTable is set to
> > another one, a plain free() may be invalid since the memory may not
> > have been allocated by libc's malloc(), calloc() or realloc().
> 
> Exactly.
> Sorry for not being exact enough, actually I didn't mention the above
> facts on purpose to not complicate things more than necessary.
Don't be sorry either, you're right: the only thing to keep in mind is
that GLib's returned memory must be free with GLib's free function. The
details generally doesn't matter.

> > And free(NULL) is always a valid call ;)
> 
> Oh, oops. I just checked free(3) on my system and it actually says that
> if NULL is passed, no operation is performed. I was quite sure that
> results in undefined behaviour. No idea how I got this idea...maybe
> it's not true for all systems (systems other than Linux, maybe some
> Unices or Windows or who knows :D).
Hmm, good question... I just checked to be sure, and C99[1] §7.20.3.2
(at least, I haven't C89 standard at hand) explicitly require free(NULL)
to do nothing -- and I'm pretty sure this is also the case with older
versions.
Then I think it's pretty safe :)

Regards,
Colomban

[1] ISO/IEC 9899 TC3 (C99 committee draft, 2007/09/07)
http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf