Prototype for auto-vivification

Author: Girgias

Zend/tests/offsets/auto-vivification-objects.phpt

@@ -0,0 +1,76 @@
+--TEST--
+Auto-vivification for objects
+--FILE--
+<?php
+
+class Vector implements DimensionFetchable, DimensionWritable, FetchAppendable {
+    private array $a = [];
+
+    private function dumpCall($method): void {
+        echo 'Object ID #', spl_object_id($this), ' called ', $method, PHP_EOL;
+    }
+
+    public function offsetExists($offset): bool {
+        $this->dumpCall(__METHOD__);
+        return array_key_exists($offset, $this->a);
+    }
+    public function offsetGet($offset): mixed {
+        $this->dumpCall(__METHOD__);
+        return $this->a[$offset];
+    }
+    public function offsetSet($offset, $value): void {
+        $this->dumpCall(__METHOD__);
+        $this->a[$offset] = $value;
+    }
+    public function &offsetFetch($offset): mixed {
+        $this->dumpCall(__METHOD__);
+        return $this->a[$offset];
+    }
+    public function append($value): void {
+        $this->dumpCall(__METHOD__);
+        $this->a[] = $value;
+    }
+    public function &fetchAppend(): mixed {
+        $this->dumpCall(__METHOD__);
+        $ref =& $this->a[];
+        return $ref;
+    }
+}
+
+$obj = new Vector();
+
+$ref = &$obj[0];
+var_dump($ref);
+
+$obj[1][] = 'append';
+$obj[2][50] = 'set-to-offset';
+
+echo "Check results\n";
+var_dump($obj[1]);
+var_dump($obj[2]);
+
+?>
+--EXPECT--
+Object ID #1 called Vector::offsetFetch
+NULL
+Object ID #1 called Vector::offsetFetch
+Object ID #2 called Vector::append
+Object ID #1 called Vector::offsetFetch
+Object ID #3 called Vector::offsetSet
+Check results
+Object ID #1 called Vector::offsetGet
+object(Vector)#2 (1) {
+  ["a":"Vector":private]=>
+  array(1) {
+    [0]=>
+    string(6) "append"
+  }
+}
+Object ID #1 called Vector::offsetGet
+object(Vector)#3 (1) {
+  ["a":"Vector":private]=>
+  array(1) {
+    [50]=>
+    string(13) "set-to-offset"
+  }
+}

Zend/zend_execute.c

@@ -3044,6 +3044,7 @@ static zend_never_inline void zend_fetch_object_dimension_address(zval *result,
 			 * $ao[] = &$var;
 			 * cases */
 			&& Z_TYPE_P(retval) != IS_INDIRECT
+			/* IS_OBJECT is to support ArrayAccess without by-ref returns */
 			&& Z_TYPE_P(retval) != IS_OBJECT
 		) {
 			zend_class_entry *ce = obj->ce;
@@ -3057,6 +3058,19 @@ static zend_never_inline void zend_fetch_object_dimension_address(zval *result,
 			ZVAL_UNDEF(result);
 			goto clean_up;
 		}
+		/* Check if we need to auto-vivify a possible null return */
+		if (Z_ISREF_P(result) && Z_ISNULL_P(Z_REFVAL_P(result))) {
+			const zend_op *next_opline = execute_data->opline + 1;
+			if (UNEXPECTED(
+				next_opline->opcode == ZEND_ASSIGN_DIM
+				|| next_opline->opcode == ZEND_ASSIGN_DIM_OP
+				|| next_opline->opcode == ZEND_FETCH_DIM_W
+				|| next_opline->opcode == ZEND_FETCH_DIM_RW
+			)) {
+				// TODO THIS IS A VERY CRUDE PROTOTYPE
+				object_init_ex(Z_REFVAL_P(result), obj->ce);
+			}
+		}
 		if (result != retval) {
 			ZVAL_INDIRECT(result, retval);
 		}