GType <=> gpointer

[muppet <scott asofyet org>]

Here's a little something i stumbled across while debugging a really 
bizarre gtk2-perl crash on alpha processors.

	type = (GType) GPOINTER_TO_UINT
			(g_hash_table_lookup (types_by_package, package));

that code results in an invalid GType on alpha.  that's because:

	#define GPOINTER_TO_UINT(p)	((guint) (gulong) (p))

and

	sizeof (GType) == sizeof (gulong)
	sizeof (guint) != sizeof (GType)

thus, the GPOINTER_TO_UINT filter has the effect of stripping the upper 
4 bytes off of the GType value, resulting in an invalid GType which 
later causes Very Bad Things to happen.

glib seems to jump through some hoops to ensure that a GType is the 
same size as the platform's pointer (actually, the size of size_t on 
that platform), but doesn't bother with the relationship to int/uint.


is it more correct to do

	type = (GType) pointer

than to use the GPOINTER_TO_UINT macro?  should there be a 
GPOINTER_TO_GTYPE/GTYPE_TO_GPOINTER pair?


interestingly, the GPOINTER_TO_UINT casts were necessary to get 
gtk2-perl working correctly on x86_64, and seem to have no ill effect 
on mips.

this also seems to imply that a G_TYPE_UINT column in a TreeModel is 
not sufficient to hold GTypes, nor would G_TYPE_ULONG always suffice.

--
muppet <scott at asofyet dot org>