[BROKEN] Experimenting with immutable arrays

Author: alexdowad

ext/mbstring/mbstring.c

@@ -1016,6 +1016,20 @@ ZEND_TSRMLS_CACHE_UPDATE();
 	mbstring_globals->internal_encoding_set = 0;
 	mbstring_globals->http_output_set = 0;
 	mbstring_globals->http_input_set = 0;
+
+	/* Initialize immutable array of supported encoding names
+	 * This is done so that we can check if `mb_list_encodings()` is being
+	 * passed to other mbstring functions using a cheap pointer equality check */
+	HashTable *array = malloc(sizeof(HashTable));
+	zend_hash_init(array, 80, NULL, NULL, true);
+	GC_ADD_FLAGS(array, IS_ARRAY_IMMUTABLE);
+	for (const mbfl_encoding **encodings = mbfl_get_supported_encodings(); *encodings; encodings++) {
+		zval tmp;
+		ZVAL_PSTRING(&tmp, (*encodings)->name);
+		zend_hash_next_index_insert(array, &tmp);
+	}
+	GC_SET_REFCOUNT(array, 2);
+	mbstring_globals->all_encodings_list = array;
 }
 /* }}} */
 
@@ -1031,6 +1045,8 @@ static PHP_GSHUTDOWN_FUNCTION(mbstring)
 	if (mbstring_globals->http_output_conv_mimetypes) {
 		_php_mb_free_regex(mbstring_globals->http_output_conv_mimetypes);
 	}
+	GC_DELREF(mbstring_globals->all_encodings_list);
+	zend_hash_destroy(mbstring_globals->all_encodings_list);
 #ifdef HAVE_MBREGEX
 	php_mb_regex_globals_free(mbstring_globals->mb_regex_globals);
 #endif
@@ -3205,10 +3221,7 @@ PHP_FUNCTION(mb_list_encodings)
 {
 	ZEND_PARSE_PARAMETERS_NONE();
 
-	array_init(return_value);
-	for (const mbfl_encoding **encodings = mbfl_get_supported_encodings(); *encodings; encodings++) {
-		add_next_index_string(return_value, (*encodings)->name);
-	}
+	RETURN_ARR(MBSTRG(all_encodings_list));
 }
 /* }}} */
 

ext/mbstring/mbstring.h

@@ -88,6 +88,7 @@ ZEND_BEGIN_MODULE_GLOBALS(mbstring)
 	size_t current_detect_order_list_size;
 	enum mbfl_no_encoding *default_detect_order_list;
 	size_t default_detect_order_list_size;
+	HashTable *all_encodings_list;
 	int filter_illegal_mode;
 	uint32_t filter_illegal_substchar;
 	int current_filter_illegal_mode;