Fix GH-18641: Accessing a BcMath\Number property by ref crashes

The properties are virtual so we need a custom get_property_ptr_ptr
handler.

Author: ndossche

ext/bcmath/bcmath.c

@@ -971,6 +971,12 @@ static zval *bcmath_number_read_property(zend_object *obj, zend_string *name, in
 	return zend_std_read_property(obj, name, type, cache_slot, rv);
 }
 
+static zval *bcmath_number_get_property_ptr_ptr(zend_object *object, zend_string *member, int type, void **cache_slot)
+{
+	/* Must always go through read property because all properties are virtual, and no dynamic properties are allowed. */
+	return NULL;
+}
+
 static int bcmath_number_has_property(zend_object *obj, zend_string *name, int check_empty, void **cache_slot)
 {
 	if (check_empty == ZEND_PROPERTY_NOT_EMPTY) {
@@ -1014,6 +1020,7 @@ static void bcmath_number_register_class(void)
 	bcmath_number_obj_handlers.unset_property = bcmath_number_unset_property;
 	bcmath_number_obj_handlers.has_property = bcmath_number_has_property;
 	bcmath_number_obj_handlers.read_property = bcmath_number_read_property;
+	bcmath_number_obj_handlers.get_property_ptr_ptr = bcmath_number_get_property_ptr_ptr;
 	bcmath_number_obj_handlers.get_properties_for = bcmath_number_get_properties_for;
 	bcmath_number_obj_handlers.cast_object = bcmath_number_cast_object;
 }

ext/bcmath/tests/number/gh18641.phpt

@@ -0,0 +1,13 @@
+--TEST--
+GH-18641 (Accessing a BcMath\Number property by ref crashes)
+--EXTENSIONS--
+bcmath
+--FILE--
+<?php
+$a = new BCMath\Number("1");
+$fusion = $a;
+$x = &$fusion->value;
+var_dump($x);
+?>
+--EXPECT--
+string(1) "1"