Implement delayed early binding for classes without parents

Normally, we add classes without parents (and no interfaces or traits) directly
to the class map, early binding the class. However, if the same class has
already been registered, we would instead just add a ZEND_DECLARE_CLASS
instruction and let the handler throw a duplicate class declaration exception.

However, with opcache, if on the next request the files are included in the
opposite order, we won't perform early binding. To fix this, create a
ZEND_DECLARE_CLASS_DELAYED instruction instead and handle classes without
parents accordingly, skipping any linking for classes that are already linked in
delayed early binding.

Fixes GH-8846

Author: iluuu1994

NEWS

@@ -35,6 +35,8 @@ PHP                                                                        NEWS
     has inherited it from its parent). (ilutov)
   . Fix bug GH-11154 (Negative indices on empty array don't affect next chosen
     index). (ColinHDev)
+  . Fix bug GH-8846 (Implement delayed early binding for classes without
+    parents). (ilutov)
 
 - Date:
   . Implement More Appropriate Date/Time Exceptions RFC. (Derick)

Zend/zend_compile.c

@@ -8057,8 +8057,11 @@ static void zend_compile_class_decl(znode *result, zend_ast *ast, bool toplevel)
 				ce->ce_flags |= ZEND_ACC_LINKED;
 				zend_observer_class_linked_notify(ce, lcname);
 				return;
+			} else {
+				goto link_unbound;
 			}
 		} else if (!extends_ast) {
+link_unbound:
 			/* Link unbound simple class */
 			zend_build_properties_info_table(ce);
 			ce->ce_flags |= ZEND_ACC_LINKED;
@@ -8098,11 +8101,17 @@ static void zend_compile_class_decl(znode *result, zend_ast *ast, bool toplevel)
 		zend_add_literal_string(&key);
 
 		opline->opcode = ZEND_DECLARE_CLASS;
-		if (extends_ast && toplevel
+		if (toplevel
 			 && (CG(compiler_options) & ZEND_COMPILE_DELAYED_BINDING)
 				/* We currently don't early-bind classes that implement interfaces or use traits */
 			 && !ce->num_interfaces && !ce->num_traits
 		) {
+			if (!extends_ast) {
+				/* Use empty string for classes without parents to avoid new handler, and special
+				 * handling of zend_early_binding. */
+				opline->op2_type = IS_CONST;
+				LITERAL_STR(opline->op2, ZSTR_EMPTY_ALLOC());
+			}
 			CG(active_op_array)->fn_flags |= ZEND_ACC_EARLY_BINDING;
 			opline->opcode = ZEND_DECLARE_CLASS_DELAYED;
 			opline->extended_value = zend_alloc_cache_slot();

Zend/zend_inheritance.c

@@ -3276,8 +3276,17 @@ ZEND_API zend_class_entry *zend_try_early_bind(zend_class_entry *ce, zend_class_
 	inheritance_status status;
 	zend_class_entry *proto = NULL;
 	zend_class_entry *orig_linking_class;
-	uint32_t is_cacheable = ce->ce_flags & ZEND_ACC_IMMUTABLE;
 
+	if (ce->ce_flags & ZEND_ACC_LINKED) {
+		ZEND_ASSERT(ce->parent == NULL);
+		if (UNEXPECTED(!register_early_bound_ce(delayed_early_binding, lcname, ce))) {
+			return NULL;
+		}
+		zend_observer_class_linked_notify(ce, lcname);
+		return ce;
+	}
+
+	uint32_t is_cacheable = ce->ce_flags & ZEND_ACC_IMMUTABLE;
 	UPDATE_IS_CACHEABLE(parent_ce);
 	if (is_cacheable) {
 		if (zend_inheritance_cache_get && zend_inheritance_cache_add) {

ext/opcache/tests/gh8846-1.inc

@@ -0,0 +1,4 @@
+<?php
+class Foo {
+	const BAR = true;
+}

ext/opcache/tests/gh8846-2.inc

@@ -0,0 +1,5 @@
+<?php
+var_dump(Foo::BAR);
+class Foo {
+	const BAR = true;
+}

ext/opcache/tests/gh8846.phpt

@@ -0,0 +1,39 @@
+--TEST--
+Bug GH-8846: Delayed early binding can be used for classes without parents
+--EXTENSIONS--
+opcache
+--CONFLICTS--
+server
+--INI--
+opcache.validate_timestamps=1
+opcache.revalidate_freq=0
+--FILE--
+<?php
+
+file_put_contents(__DIR__ . '/gh8846-index.php', <<<'PHP'
+<?php
+if (!@$_GET['skip']) {
+    include __DIR__ . '/gh8846-1.inc';
+}
+include __DIR__ . '/gh8846-2.inc';
+echo "Ok\n";
+PHP);
+
+include 'php_cli_server.inc';
+php_cli_server_start('-d opcache.enable=1 -d opcache.enable_cli=1');
+
+echo file_get_contents('http://' . PHP_CLI_SERVER_ADDRESS . '/gh8846-index.php');
+echo "\n";
+echo file_get_contents('http://' . PHP_CLI_SERVER_ADDRESS . '/gh8846-index.php?skip=1');
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__ . '/gh8846-index.php');
+?>
+--EXPECTF--
+bool(true)
+<br />
+<b>Fatal error</b>:  Cannot declare class Foo, because the name is already in use in <b>%sgh8846-2.inc</b> on line <b>%d</b><br />
+
+bool(true)
+Ok

ext/opcache/zend_accelerator_util_funcs.c

@@ -357,9 +357,10 @@ static void zend_accel_do_delayed_early_binding(
 			zval *zv = zend_hash_find_known_hash(EG(class_table), early_binding->rtd_key);
 			if (zv) {
 				zend_class_entry *orig_ce = Z_CE_P(zv);
-				zend_class_entry *parent_ce =
-					zend_hash_find_ex_ptr(EG(class_table), early_binding->lc_parent_name, 1);
-				if (parent_ce) {
+				zend_class_entry *parent_ce = !(orig_ce->ce_flags & ZEND_ACC_LINKED)
+					? zend_hash_find_ex_ptr(EG(class_table), early_binding->lc_parent_name, 1)
+					: NULL;
+				if (parent_ce || (orig_ce->ce_flags & ZEND_ACC_LINKED)) {
 					ce = zend_try_early_bind(orig_ce, parent_ce, early_binding->lcname, zv);
 				}
 			}