[mono][sgen] Fix detection of weakref objects (#77170)

Comparison with klass mono_defaults.generic_weakreference_class was broken because that class is a generic class while the objects have as a class generic instantiations of that so the comparison would fail. Simplify the code by adding a new gc bit where we can use name comparison.
dotnet · Oct 19, 2022 · 31d4e3a · 31d4e3a
1 parent b8653dd
commit 31d4e3a
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Showing 4 changed files with 8 additions and 9 deletions.
diff --git a/src/mono/mono/metadata/class-internals.h b/src/mono/mono/metadata/class-internals.h
@@ -921,8 +921,6 @@ typedef struct {
 	MonoClass *generic_ienumerator_class;
 	MonoClass *alc_class;
 	MonoClass *appcontext_class;
-	MonoClass *weakreference_class;
-	MonoClass *generic_weakreference_class;
 } MonoDefaults;
 
 /* If you need a MonoType, use one of the mono_get_*_type () functions in class-inlines.h */

diff --git a/src/mono/mono/metadata/domain.c b/src/mono/mono/metadata/domain.c
@@ -290,11 +290,6 @@ mono_init_internal (const char *root_domain_name)
 	mono_defaults.alc_class = mono_class_get_assembly_load_context_class ();
 	mono_defaults.appcontext_class = mono_class_try_load_from_name (mono_defaults.corlib, "System", "AppContext");
 
-	mono_defaults.weakreference_class = mono_class_try_load_from_name (
-	        mono_defaults.corlib, "System", "WeakReference");
-	mono_defaults.generic_weakreference_class = mono_class_try_load_from_name (
-	        mono_defaults.corlib, "System", "WeakReference`1");
-
 	// in the past we got a filename as the root_domain_name so try to get the basename
 	domain->friendly_name = g_path_get_basename (root_domain_name);
 

diff --git a/src/mono/mono/metadata/sgen-mono.c b/src/mono/mono/metadata/sgen-mono.c
@@ -444,6 +444,12 @@ mono_gc_get_vtable_bits (MonoClass *klass)
 		if (fin_callbacks.is_class_finalization_aware (klass))
 			res |= SGEN_GC_BIT_FINALIZER_AWARE;
 	}
+
+	if (m_class_get_image (klass) == mono_defaults.corlib &&
+			strcmp (m_class_get_name_space (klass), "System") == 0 &&
+			strncmp (m_class_get_name (klass), "WeakReference", 13) == 0)
+		res |= SGEN_GC_BIT_WEAKREF;
+
 	return res;
 }
 
@@ -457,8 +463,7 @@ is_finalization_aware (MonoObject *obj)
 gboolean
 sgen_client_object_finalize_eagerly (GCObject *obj)
 {
-	if (obj->vtable->klass == mono_defaults.weakreference_class ||
-	    obj->vtable->klass == mono_defaults.generic_weakreference_class) {
+	if (obj->vtable->gc_bits & SGEN_GC_BIT_WEAKREF) {
 		MonoWeakReference *wr = (MonoWeakReference*)obj;
 		MonoGCHandle gc_handle = (MonoGCHandle)(wr->handleAndKind & ~(gsize)1);
 		mono_gchandle_free_internal (gc_handle);

diff --git a/src/mono/mono/sgen/sgen-gc.h b/src/mono/mono/sgen/sgen-gc.h
@@ -300,6 +300,7 @@ enum {
 	SGEN_GC_BIT_BRIDGE_OBJECT = 1,
 	SGEN_GC_BIT_BRIDGE_OPAQUE_OBJECT = 2,
 	SGEN_GC_BIT_FINALIZER_AWARE = 4,
+	SGEN_GC_BIT_WEAKREF = 8,
 };
 
 void sgen_gc_init (void)