Fix GH-9883 SplFileObject::__toString() reads next line

We need to overwrite the __toString magic method for SplFileObject, similarly to how DirectoryIterator overwrites it
Moreover, the custom cast handler is useless as we define __toString methods, so use the standard one instead.

Author: Girgias

ext/spl/spl_directory.c

@@ -1828,34 +1828,6 @@ zend_object_iterator *spl_filesystem_tree_get_iterator(zend_class_entry *ce, zva
 }
 /* }}} */
 
-/* {{{ spl_filesystem_object_cast */
-static int spl_filesystem_object_cast(zend_object *readobj, zval *writeobj, int type)
-{
-	spl_filesystem_object *intern = spl_filesystem_from_obj(readobj);
-
-	if (type == IS_STRING) {
-		if (readobj->ce->__tostring) {
-			return zend_std_cast_object_tostring(readobj, writeobj, type);
-		}
-
-		switch (intern->type) {
-		case SPL_FS_INFO:
-		case SPL_FS_FILE:
-			ZVAL_STRINGL(writeobj, intern->file_name, intern->file_name_len);
-			return SUCCESS;
-		case SPL_FS_DIR:
-			ZVAL_STRING(writeobj, intern->u.dir.entry.d_name);
-			return SUCCESS;
-		}
-	} else if (type == _IS_BOOL) {
-		ZVAL_TRUE(writeobj);
-		return SUCCESS;
-	}
-	ZVAL_NULL(writeobj);
-	return FAILURE;
-}
-/* }}} */
-
 static zend_result spl_filesystem_file_read_ex(spl_filesystem_object *intern, bool silent, zend_long line_add) /* {{{ */
 {
 	char *buf;
@@ -2750,14 +2722,31 @@ PHP_METHOD(SplFileObject, seek)
 	}
 } /* }}} */
 
+PHP_METHOD(SplFileObject, __toString)
+{
+	if (zend_parse_parameters_none() == FAILURE) {
+		RETURN_THROWS();
+	}
+
+	spl_filesystem_object *intern = Z_SPLFILESYSTEM_P(ZEND_THIS);
+
+	CHECK_SPL_FILE_OBJECT_IS_INITIALIZED(intern);
+
+	if (!intern->u.file.current_line && Z_ISUNDEF(intern->u.file.current_zval)) {
+		spl_filesystem_file_read_line(ZEND_THIS, intern, 1);
+	}
+
+	RETURN_STRINGL(intern->u.file.current_line, intern->u.file.current_line_len);
+}
+
 /* {{{ PHP_MINIT_FUNCTION(spl_directory) */
 PHP_MINIT_FUNCTION(spl_directory)
 {
 	REGISTER_SPL_STD_CLASS_EX(SplFileInfo, spl_filesystem_object_new, class_SplFileInfo_methods);
 	memcpy(&spl_filesystem_object_handlers, &std_object_handlers, sizeof(zend_object_handlers));
 	spl_filesystem_object_handlers.offset = XtOffsetOf(spl_filesystem_object, std);
 	spl_filesystem_object_handlers.clone_obj = spl_filesystem_object_clone;
-	spl_filesystem_object_handlers.cast_object = spl_filesystem_object_cast;
+	spl_filesystem_object_handlers.cast_object = zend_std_cast_object_tostring;
 	spl_filesystem_object_handlers.dtor_obj = spl_filesystem_object_destroy_object;
 	spl_filesystem_object_handlers.free_obj = spl_filesystem_object_free_storage;
 	spl_ce_SplFileInfo->serialize = zend_class_serialize_deny;

ext/spl/spl_directory.stub.php

@@ -286,7 +286,6 @@ public function seek(int $line) {}
      */
     public function getCurrentLine() {}
 
-    /** @implementation-alias SplFileObject::fgets */
     public function __toString(): string {}
 }
 

ext/spl/spl_directory_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: d9110bb238c9edb5c013bd482649ed96e24ff7b6 */
+ * Stub hash: d60261a3b0678ccb1184e67dd99a57014ecf5c3e */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_SplFileInfo___construct, 0, 0, 1)
 	ZEND_ARG_TYPE_INFO(0, filename, IS_STRING, 0)
@@ -342,6 +342,7 @@ ZEND_METHOD(SplFileObject, getMaxLineLen);
 ZEND_METHOD(SplFileObject, hasChildren);
 ZEND_METHOD(SplFileObject, getChildren);
 ZEND_METHOD(SplFileObject, seek);
+ZEND_METHOD(SplFileObject, __toString);
 ZEND_METHOD(SplTempFileObject, __construct);
 
 
@@ -462,7 +463,7 @@ static const zend_function_entry class_SplFileObject_methods[] = {
 	ZEND_ME(SplFileObject, getChildren, arginfo_class_SplFileObject_getChildren, ZEND_ACC_PUBLIC)
 	ZEND_ME(SplFileObject, seek, arginfo_class_SplFileObject_seek, ZEND_ACC_PUBLIC)
 	ZEND_MALIAS(SplFileObject, getCurrentLine, fgets, arginfo_class_SplFileObject_getCurrentLine, ZEND_ACC_PUBLIC)
-	ZEND_MALIAS(SplFileObject, __toString, fgets, arginfo_class_SplFileObject___toString, ZEND_ACC_PUBLIC)
+	ZEND_ME(SplFileObject, __toString, arginfo_class_SplFileObject___toString, ZEND_ACC_PUBLIC)
 	ZEND_FE_END
 };
 

ext/spl/tests/gh9883-extra.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Bug GH-9883 (SplFileObject::__toString() reads next line)
+--FILE--
+<?php
+$file_stream = new SplTempFileObject();
+
+echo $file_stream; // line 4
+echo $file_stream; // line 5
+echo $file_stream; // line 6
+echo $file_stream; // line 7
+echo $file_stream; // line 8
+echo $file_stream; // line 9
+?>
+--EXPECT--

ext/spl/tests/gh9883.phpt

@@ -0,0 +1,20 @@
+--TEST--
+Bug GH-9883 (SplFileObject::__toString() reads next line)
+--FILE--
+<?php
+$file_stream = new SplFileObject(__FILE__, 'rb');
+
+echo $file_stream; // line 4
+echo $file_stream; // line 5
+echo $file_stream; // line 6
+echo $file_stream; // line 7
+echo $file_stream; // line 8
+echo $file_stream; // line 9
+?>
+--EXPECT--
+<?php
+<?php
+<?php
+<?php
+<?php
+<?php