Re: newbie question about g_object unref()

[Luis Lopez <luis lopez cuarentaydos com>]

El 19/11/10 14:36, David NeÄas escribiÃ:
> If you want to nullify a pointer when you release your reference (which
> I also find often useful as once you released your reference you may not
> be longer sure the object exists at all) you should use a macro for
> that, I use one defined approximately
>
>      do { if (obj) { g_object_unref(obj); (obj) = NULL; } } while (0)
>
> which, beside nullifying the pointer, is idempotent and can also be
> freely used on NULL pointer.

I use a generic solution which handles this case for strings, gobjects, 
g(s)list (not deep free), etc...

#define gel_free_and_invalidate(obj,value,func) \
    do { \
        if (obj != value)  \
        { \
            func(obj); \
            obj = value; \
        } \
    } while(0)

#define gel_free_and_invalidate_with_args(obj,value,func,...) \
    do { \
        if (obj != value)  \
        { \
            func(obj, __VA_ARGS__); \
            obj = value; \
        } \
    } while(0)


In the case of unref and nullify a GObject you can use this:
gel_free_and_invalidate(o, NULL, g_object_unref);

for strings:
gel_free_and_invalidate(str, NULL, g_free);

g_source ids:
gel_free_and_invalidate(id, 0, g_source_remove);

etc..