Re: [PATCH] fix crashing on amd64

[Torsten Schoenfeld <kaffeetisch gmx de>]

On Wed, 2006-01-11 at 16:29 +0100, Thierry Vignaud wrote:

> On x86_64, the conversions from ptr to int and from int to ptr will
> loose the highest bits of the pointer, leading to memory access
> violations. Use the safer macros that perl provides instead.

Applied to HEAD, is present in Glib 1.114.  I had to add some casts to
avoid compiler warnings, though:

@@ -552,7 +552,7 @@ gobject_destroy_wrapper (SV *obj)
         warn ("gobject_destroy_wrapper (%p)[%d]", obj,
               SvREFCNT ((SV*)REVIVE_UNDEAD(obj)));
 #endif
-        obj = REVIVE_UNDEAD(obj);
+        obj = (SV *) REVIVE_UNDEAD(obj);
         sv_unmagic (obj, PERL_MAGIC_ext);

         /* we might want to optimize away the call to DESTROY here for non-perl classes. */
@@ -733,7 +733,7 @@ gperl_new_object (GObject * object,
                 /* if the SV is undead, revive it */
                 if (IS_UNDEAD(obj)) {
                     g_object_ref (object);
-                    obj = REVIVE_UNDEAD(obj);
+                    obj = (SV *) REVIVE_UNDEAD(obj);
                     update_wrapper (object, obj);
                     sv = newRV_noinc (obj);
                     /* printf("reviving undead wrapper for [%p] (%p)\n", object, obj); */
@@ -892,7 +892,7 @@ _gperl_fetch_wrapper_key (GObject * obje

        /* we don't care whether the wrapper is alive or undead.  forcibly
         * remove the undead bit, or the pointer will be unusable. */
-       wrapper_hash = REVIVE_UNDEAD (wrapper_hash);
+       wrapper_hash = (HV *) REVIVE_UNDEAD (wrapper_hash);

        svname = newSVpv (name, strlen (name));
        svp = hv_fetch (wrapper_hash, SvPV_nolen (svname), SvLEN (svname)-1,
@@ -1007,7 +1007,7 @@ DESTROY (SV *sv)
                 if (object->ref_count > 1) {
                     /* become undead */
                     SV *obj = SvRV(sv);
-                    update_wrapper (object, MAKE_UNDEAD(obj));
+                    update_wrapper (object, (SV *) MAKE_UNDEAD(obj));
                     /* printf("zombies! [%p] (%p)\n", object, obj);*/
                 }
         }

Is there a safe way to avoid these?  Perhaps by using these?

#define IS_UNDEAD(x) (PTR2UV(x) & 1)
#define MAKE_UNDEAD(x) INT2PTR(gpointer,PTR2UV(x) | 1)
#define REVIVE_UNDEAD(x) INT2PTR(gpointer,PTR2UV(x) & ~1)

Or will that break on 64-bit platforms again?

If this issue is settled, the patch can go into stable-1-10 and a new
stable release can be made.

-- 
Bye,
-Torsten