Don't build prop table during json_encode(JsonSerializable)

Save memory and time by not building/updating the property table.

When performing infinite recursion detection on objects,
always check it on the object rather than its property table.

This reduces the additional memory usage for both internal and userland
implementations of JsonSerializable caused by json_encode.
It does this by avoiding creating the properties table for the first time.
(Classes such as SplFixedArray both implement JsonSerializable and override
get_properties)

This change also makes the method of infinite recursion detection consistent
with the special case for standard classes from
f9f8c1c

Author: TysonAndre

ext/json/json_encoder.c

@@ -534,20 +534,20 @@ static zend_result php_json_escape_string(
 
 static zend_result php_json_encode_serializable_object(smart_str *buf, zval *val, int options, php_json_encoder *encoder) /* {{{ */
 {
+	zend_object *obj = Z_OBJ_P(val);
 	zend_class_entry *ce = Z_OBJCE_P(val);
-	HashTable* myht = Z_OBJPROP_P(val);
 	zval retval, fname;
 	zend_result return_code;
 
-	if (myht && GC_IS_RECURSIVE(myht)) {
+	if (GC_IS_RECURSIVE(obj)) {
 		encoder->error_code = PHP_JSON_ERROR_RECURSION;
 		if (options & PHP_JSON_PARTIAL_OUTPUT_ON_ERROR) {
 			smart_str_appendl(buf, "null", 4);
 		}
 		return FAILURE;
 	}
 
-	PHP_JSON_HASH_PROTECT_RECURSION(myht);
+	GC_PROTECT_RECURSION(obj);
 
 	ZVAL_STRING(&fname, "jsonSerialize");
 
@@ -560,7 +560,7 @@ static zend_result php_json_encode_serializable_object(smart_str *buf, zval *val
 		if (options & PHP_JSON_PARTIAL_OUTPUT_ON_ERROR) {
 			smart_str_appendl(buf, "null", 4);
 		}
-		PHP_JSON_HASH_UNPROTECT_RECURSION(myht);
+		GC_UNPROTECT_RECURSION(obj);
 		return FAILURE;
 	}
 
@@ -572,19 +572,19 @@ static zend_result php_json_encode_serializable_object(smart_str *buf, zval *val
 		if (options & PHP_JSON_PARTIAL_OUTPUT_ON_ERROR) {
 			smart_str_appendl(buf, "null", 4);
 		}
-		PHP_JSON_HASH_UNPROTECT_RECURSION(myht);
+		GC_UNPROTECT_RECURSION(obj);
 		return FAILURE;
 	}
 
 	if ((Z_TYPE(retval) == IS_OBJECT) &&
 		(Z_OBJ(retval) == Z_OBJ_P(val))) {
 		/* Handle the case where jsonSerialize does: return $this; by going straight to encode array */
-		PHP_JSON_HASH_UNPROTECT_RECURSION(myht);
+		GC_UNPROTECT_RECURSION(obj);
 		return_code = php_json_encode_array(buf, &retval, options, encoder);
 	} else {
 		/* All other types, encode as normal */
 		return_code = php_json_encode_zval(buf, &retval, options, encoder);
-		PHP_JSON_HASH_UNPROTECT_RECURSION(myht);
+		GC_UNPROTECT_RECURSION(obj);
 	}
 
 	zval_ptr_dtor(&retval);

ext/json/tests/bug77843.phpt

@@ -18,8 +18,5 @@ var_dump(json_encode([&$arr]));
 
 ?>
 --EXPECT--
-object(X)#1 (1) {
-  ["prop"]=>
-  string(5) "value"
-}
+*RECURSION*
 string(20) "[[{"prop":"value"}]]"