zend_compile_implements() assumes that the class entry has no interfaces already

[DanielEScherzer]

Description

See

php-src/Zend/zend_compile.c

Lines 8959 to 8977 in b0c7865

	static void zend_compile_implements(zend_ast *ast) /* {{{ */
	{
	zend_ast_list *list = zend_ast_get_list(ast);
	zend_class_entry *ce = CG(active_class_entry);
	zend_class_name *interface_names;
	uint32_t i;
	interface_names = emalloc(sizeof(zend_class_name) * list->children);
	for (i = 0; i < list->children; ++i) {
	zend_ast *class_ast = list->child[i];
	interface_names[i].name =
	zend_resolve_const_class_name_reference(class_ast, "interface name");
	interface_names[i].lc_name = zend_string_tolower(interface_names[i].name);
	}
	ce->num_interfaces = list->children;
	ce->interface_names = interface_names;
	}

If an attribute validator added an interface to the class, it gets silently dropped and triggers leaks, because class attributes are compiled before implements, see

php-src/Zend/zend_compile.c

Lines 9110 to 9116 in b0c7865

	if (decl->child[3]) {
	zend_compile_attributes(&ce->attributes, decl->child[3], 0, ZEND_ATTRIBUTE_TARGET_CLASS, 0);
	}
	if (implements_ast) {
	zend_compile_implements(implements_ast);
	}

Discovered while working on https://github.com/DanielEScherzer/CustomCast, not sure if I noticed this earlier and just didn't report it but it has been there for a while

PHP Version

8.4+

Operating System

No response