[src/trunk]: src/usr.bin/xlint/lint1 lint: only allow GCC attribute in null s...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/02952e1b8665
branches:  trunk
changeset: 365857:02952e1b8665
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri Apr 29 07:02:40 2022 +0000

description:
lint: only allow GCC attribute in null statement

The only indented usage in that position is a fallthrough statement, as
a replacement for a /* FALLTHROUGH */ comment.  There is no point in
using _Noreturn or _Alignas as a statement.

Ideally, instead of gcc_attribute, the grammar would allow
gcc_attribute_list here (as always with GCC attributes), but that would
have introduced a reduce/reduce conflict, due to the attributes in the
middle of labeled_statement.

diffstat:

 usr.bin/xlint/lint1/cgram.y |  6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diffs (28 lines):

diff -r 4fc1b12ce985 -r 02952e1b8665 usr.bin/xlint/lint1/cgram.y
--- a/usr.bin/xlint/lint1/cgram.y       Fri Apr 29 06:59:29 2022 +0000
+++ b/usr.bin/xlint/lint1/cgram.y       Fri Apr 29 07:02:40 2022 +0000
@@ -1,5 +1,5 @@
 %{
-/* $NetBSD: cgram.y,v 1.404 2022/04/29 06:40:51 rillig Exp $ */
+/* $NetBSD: cgram.y,v 1.405 2022/04/29 07:02:40 rillig Exp $ */
 
 /*
  * Copyright (c) 1996 Christopher G. Demetriou.  All Rights Reserved.
@@ -35,7 +35,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: cgram.y,v 1.404 2022/04/29 06:40:51 rillig Exp $");
+__RCSID("$NetBSD: cgram.y,v 1.405 2022/04/29 07:02:40 rillig Exp $");
 #endif
 
 #include <limits.h>
@@ -1643,7 +1643,7 @@
        ;
 
 non_expr_statement:            /* helper for C99 6.8 */
-         type_attribute T_SEMI
+         gcc_attribute /* ((__fallthrough__)) */ T_SEMI
        | labeled_statement
        | compound_statement
        | selection_statement