Implement GH-9826: Make class_alias() work with internal classes

UPGRADING

@@ -57,6 +57,7 @@ PHP 8.3 UPGRADE NOTES
     "full" => bool
     "buffer_size" => int
     See GH-9336
+  . class_alias() now supports creating an alias of an internal class.
 
 - MBString:
   . mb_strtolower, mb_strtotitle, and mb_convert_case implement conditional

UPGRADING.INTERNALS

@@ -30,6 +30,10 @@ PHP 8.3 INTERNALS UPGRADE NOTES
   for C99 features have been removed and therefore macro definitions
   from php_config.h have disappeared.  Do not use those feature
   macros.
+* Internal class aliases created during request time can now exist in
+  the class table. zend_register_class_alias_ex() will not increase
+  the refcount for class aliases and the cleanup function takes this
+  into account.
 
 ========================
 2. Build system changes

Zend/Optimizer/zend_optimizer.c

@@ -1416,8 +1416,7 @@ static void zend_foreach_op_array_helper(
 
 void zend_foreach_op_array(zend_script *script, zend_op_array_func_t func, void *context)
 {
-	zend_class_entry *ce;
-	zend_string *key;
+	zval *zv;
 	zend_op_array *op_array;
 
 	zend_foreach_op_array_helper(&script->main_op_array, func, context);
@@ -1426,10 +1425,11 @@ void zend_foreach_op_array(zend_script *script, zend_op_array_func_t func, void
 		zend_foreach_op_array_helper(op_array, func, context);
 	} ZEND_HASH_FOREACH_END();
 
-	ZEND_HASH_MAP_FOREACH_STR_KEY_PTR(&script->class_table, key, ce) {
-		if (ce->refcount > 1 && !zend_string_equals_ci(key, ce->name)) {
+	ZEND_HASH_MAP_FOREACH_VAL(&script->class_table, zv) {
+		if (Z_TYPE_P(zv) == IS_ALIAS_PTR) {
 			continue;
 		}
+		zend_class_entry *ce = Z_CE_P(zv);
 		ZEND_HASH_MAP_FOREACH_PTR(&ce->function_table, op_array) {
 			if (op_array->scope == ce
 					&& op_array->type == ZEND_USER_FUNCTION
@@ -1465,11 +1465,10 @@ static void zend_optimizer_call_registered_passes(zend_script *script, void *ctx
 
 ZEND_API void zend_optimize_script(zend_script *script, zend_long optimization_level, zend_long debug_level)
 {
-	zend_class_entry *ce;
-	zend_string *key;
 	zend_op_array *op_array;
 	zend_string *name;
 	zend_optimizer_ctx ctx;
+	zval *zv;
 
 	ctx.arena = zend_arena_create(64 * 1024);
 	ctx.script = script;
@@ -1596,10 +1595,11 @@ ZEND_API void zend_optimize_script(zend_script *script, zend_long optimization_l
 		}
 	}
 
-	ZEND_HASH_MAP_FOREACH_STR_KEY_PTR(&script->class_table, key, ce) {
-		if (ce->refcount > 1 && !zend_string_equals_ci(key, ce->name)) {
+	ZEND_HASH_MAP_FOREACH_VAL(&script->class_table, zv) {
+		if (Z_TYPE_P(zv) == IS_ALIAS_PTR) {
 			continue;
 		}
+		zend_class_entry *ce = Z_CE_P(zv);
 		ZEND_HASH_MAP_FOREACH_STR_KEY_PTR(&ce->function_table, name, op_array) {
 			if (op_array->scope != ce && op_array->type == ZEND_USER_FUNCTION) {
 				zend_op_array *orig_op_array =

Zend/tests/class_alias_006.phpt

@@ -3,12 +3,11 @@ Testing creation of alias to an internal class
 --FILE--
 <?php
 
-try {
-    class_alias('stdclass', 'foo');
-} catch (ValueError $exception) {
-    echo $exception->getMessage() . "\n";
-}
+class_alias('stdclass', 'foo');
+$foo = new foo();
+var_dump($foo);
 
 ?>
 --EXPECT--
-class_alias(): Argument #1 ($class) must be a user-defined class name, internal class name given
+object(stdClass)#1 (0) {
+}

Zend/zend_API.c

@@ -3302,13 +3302,15 @@ ZEND_API zend_result zend_register_class_alias_ex(const char *name, size_t name_
 
 	lcname = zend_new_interned_string(lcname);
 
+	/* We cannot increase the refcount of an internal class during request time.
+	 * Instead of having to deal with differentiating between class types and lifetimes,
+	 * we simply don't increase the refcount of a class entry for aliases.
+	 */
 	ZVAL_ALIAS_PTR(&zv, ce);
+
 	ret = zend_hash_add(CG(class_table), lcname, &zv);
 	zend_string_release_ex(lcname, 0);
 	if (ret) {
-		if (!(ce->ce_flags & ZEND_ACC_IMMUTABLE)) {
-			ce->refcount++;
-		}
 		// avoid notifying at MINIT time
 		if (ce->type == ZEND_USER_CLASS) {
 			zend_observer_class_linked_notify(ce, lcname);

Zend/zend_builtin_functions.c

@@ -1074,16 +1074,11 @@ ZEND_FUNCTION(class_alias)
 	ce = zend_lookup_class_ex(class_name, NULL, !autoload ? ZEND_FETCH_CLASS_NO_AUTOLOAD : 0);
 
 	if (ce) {
-		if (ce->type == ZEND_USER_CLASS) {
-			if (zend_register_class_alias_ex(ZSTR_VAL(alias_name), ZSTR_LEN(alias_name), ce, 0) == SUCCESS) {
-				RETURN_TRUE;
-			} else {
-				zend_error(E_WARNING, "Cannot declare %s %s, because the name is already in use", zend_get_object_type(ce), ZSTR_VAL(alias_name));
-				RETURN_FALSE;
-			}
+		if (zend_register_class_alias_ex(ZSTR_VAL(alias_name), ZSTR_LEN(alias_name), ce, false) == SUCCESS) {
+			RETURN_TRUE;
 		} else {
-			zend_argument_value_error(1, "must be a user-defined class name, internal class name given");
-			RETURN_THROWS();
+			zend_error(E_WARNING, "Cannot declare %s %s, because the name is already in use", zend_get_object_type(ce), ZSTR_VAL(alias_name));
+			RETURN_FALSE;
 		}
 	} else {
 		zend_error(E_WARNING, "Class \"%s\" not found", ZSTR_VAL(class_name));

Zend/zend_opcode.c

@@ -301,6 +301,12 @@ ZEND_API void destroy_zend_class(zval *zv)
 		return;
 	}
 
+	/* We don't increase the refcount for class aliases,
+	 * skip the destruction of aliases entirely. */
+	if (UNEXPECTED(Z_TYPE_INFO_P(zv) == IS_ALIAS_PTR)) {
+		return;
+	}
+
 	if (ce->ce_flags & ZEND_ACC_FILE_CACHED) {
 		zend_class_constant *c;
 		zval *p, *end;
@@ -323,6 +329,8 @@ ZEND_API void destroy_zend_class(zval *zv)
 		return;
 	}
 
+	ZEND_ASSERT(ce->refcount > 0);
+
 	if (--ce->refcount > 0) {
 		return;
 	}
@@ -516,7 +524,7 @@ void zend_class_add_ref(zval *zv)
 {
 	zend_class_entry *ce = Z_PTR_P(zv);
 
-	if (!(ce->ce_flags & ZEND_ACC_IMMUTABLE)) {
+	if (Z_TYPE_P(zv) != IS_ALIAS_PTR && !(ce->ce_flags & ZEND_ACC_IMMUTABLE)) {
 		ce->refcount++;
 	}
 }

ext/opcache/zend_accelerator_module.c

@@ -700,15 +700,15 @@ ZEND_FUNCTION(opcache_get_status)
 		}
 
 		if (zend_hash_num_elements(&ZCSG(preload_script)->script.class_table)) {
-			zend_class_entry *ce;
+			zval *zv;
 			zend_string *key;
 
 			array_init(&scripts);
-			ZEND_HASH_MAP_FOREACH_STR_KEY_PTR(&ZCSG(preload_script)->script.class_table, key, ce) {
-				if (ce->refcount > 1 && !zend_string_equals_ci(key, ce->name)) {
+			ZEND_HASH_MAP_FOREACH_STR_KEY_VAL(&ZCSG(preload_script)->script.class_table, key, zv) {
+				if (Z_TYPE_P(zv) == IS_ALIAS_PTR) {
 					add_next_index_str(&scripts, key);
 				} else {
-					add_next_index_str(&scripts, ce->name);
+					add_next_index_str(&scripts, Z_CE_P(zv)->name);
 				}
 			} ZEND_HASH_FOREACH_END();
 			add_assoc_zval(&statistics, "classes", &scripts);