Fix accidentally inherited default value in overridden virtual properties

Discovered when working on phpGH-17376.

Author: iluuu1994

NEWS

@@ -5,6 +5,8 @@ PHP                                                                        NEWS
 - Core:
   . Fixed property hook backing value access in multi-level inheritance.
     (ilutov)
+  . Fixed accidentally inherited default value in overridden virtual properties.
+    (ilutov)
 
 27 Feb 2025, PHP 8.4.5
 

Zend/tests/property_hooks/default_value_inheritance.phpt

@@ -0,0 +1,54 @@
+--TEST--
+Property default values are not inherited
+--FILE--
+<?php
+
+class P {
+    public $a = 1;
+    public int $b = 1;
+    public $c = 1;
+    public int $d = 1;
+}
+
+class C extends P {
+    public $a { get => parent::$a::get(); }
+    public int $b { get => parent::$b::get(); }
+    public $c = 2 { get => parent::$c::get(); }
+    public int $d = 2 { get => parent::$d::get(); }
+}
+
+class GC extends C {
+    public $a { get => parent::$a::get(); }
+    public int $b { get => parent::$b::get(); }
+    public $c { get => parent::$c::get(); }
+    public int $d { get => parent::$d::get(); }
+}
+
+function test(P $p) {
+    var_dump($p->a);
+    try {
+        var_dump($p->b);
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
+    var_dump($p->c);
+    try {
+        var_dump($p->d);
+    } catch (Error $e) {
+        echo $e->getMessage(), "\n";
+    }
+}
+
+test(new C);
+test(new GC);
+
+?>
+--EXPECT--
+NULL
+Typed property C::$b must not be accessed before initialization
+int(2)
+int(2)
+NULL
+Typed property GC::$b must not be accessed before initialization
+NULL
+Typed property GC::$d must not be accessed before initialization

Zend/tests/property_hooks/dump.phpt

@@ -34,7 +34,7 @@ class Test {
 }
 
 class Child extends Test {
-    public $addedHooks {
+    public $addedHooks = 'addedHooks' {
         get { return strtoupper(parent::$addedHooks::get()); }
     }
     private $changed = 'changed Child' {

Zend/tests/property_hooks/generator_hook_002.phpt

@@ -8,7 +8,7 @@ class A {
 }
 
 class B extends A {
-    public $prop {
+    public $prop = 42 {
         get {
             yield parent::$prop::get() + 1;
             yield parent::$prop::get() + 2;

Zend/tests/property_hooks/parent_get_plain.phpt

@@ -8,7 +8,7 @@ class P {
 }
 
 class C extends P {
-    public $prop {
+    public $prop = 42 {
         get => parent::$prop::get();
     }
 }

Zend/zend_inheritance.c

@@ -1478,14 +1478,21 @@ static void do_inherit_property(zend_property_info *parent_info, zend_string *ke
 				zend_error_noreturn(E_COMPILE_ERROR, "Access level to %s::$%s must be %s (as in class %s)%s", ZSTR_VAL(ce->name), ZSTR_VAL(key), zend_visibility_string(parent_info->flags), ZSTR_VAL(parent_info->ce->name), (parent_info->flags&ZEND_ACC_PUBLIC) ? "" : " or weaker");
 			}
 			if (!(child_info->flags & ZEND_ACC_STATIC) && !(parent_info->flags & ZEND_ACC_VIRTUAL)) {
+				int parent_num = OBJ_PROP_TO_NUM(parent_info->offset);
 				if (child_info->offset != ZEND_VIRTUAL_PROPERTY_OFFSET) {
-					int parent_num = OBJ_PROP_TO_NUM(parent_info->offset);
 					int child_num = OBJ_PROP_TO_NUM(child_info->offset);
 
 					/* Don't keep default properties in GC (they may be freed by opcache) */
 					zval_ptr_dtor_nogc(&(ce->default_properties_table[parent_num]));
 					ce->default_properties_table[parent_num] = ce->default_properties_table[child_num];
 					ZVAL_UNDEF(&ce->default_properties_table[child_num]);
+				} else {
+					/* Default value was removed in child, remove it from parent too. */
+					if (ZEND_TYPE_IS_SET(child_info->type)) {
+						ZVAL_UNDEF(&ce->default_properties_table[parent_num]);
+					} else {
+						ZVAL_NULL(&ce->default_properties_table[parent_num]);
+					}
 				}
 
 				child_info->offset = parent_info->offset;