Zend/zend_variables: add _Static_assert on the size zend_rc_dtor_func

_Static_assert is C11, but has been supported since GCC 4.6.

Author: MaxKellermann

Zend/zend_variables.c

@@ -51,6 +51,11 @@ static const zend_rc_dtor_func_t zend_rc_dtor_func[] = {
 	[IS_CONSTANT_AST] = (zend_rc_dtor_func_t)zend_ast_ref_destroy
 };
 
+#if ZEND_GCC_VERSION >= 4006 || defined(__clang__)
+_Static_assert(sizeof(zend_rc_dtor_func) / sizeof(zend_rc_dtor_func[0]) == _IS_REGULAR_END,
+	       "zend_rc_dtor_func has the wrong size");
+#endif
+
 ZEND_API void ZEND_FASTCALL rc_dtor_func(zend_refcounted *p)
 {
 	ZEND_ASSERT(GC_TYPE(p) <= IS_CONSTANT_AST);