linux-kernel - Re: New -Werror=restrict error with incremental gcc

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Date:   Thu, 15 Mar 2018 22:11:54 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: New -Werror=restrict error with incremental gcc

On Thu, Mar 15, 2018 at 08:06:26AM -0700, Laura Abbott wrote:
> This only showed up with the very latest rawhide snapshot, .17 worked and
> .18 started failing. I had to download .18 manually to test locally
> https://koji.fedoraproject.org/koji/packageinfo?packageID=40

I also see the error with the latest gcc master branch.  The code is
harmless, but maybe the warning is useful in other places, so here's one
way to fix it.

----

From: Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH] objtool, perf: Fix GCC 8 -Wrestrict error

Starting with recent GCC 8 builds, objtool and perf fail to build with
the following error:

  ../str_error_r.c: In function ‘str_error_r’:
  ../str_error_r.c:25:3: error: passing argument 1 to restrict-qualified parameter aliases with argument 5 [-Werror=restrict]
     snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);

The code seems harmless, but there's probably no benefit in printing the
'buf' pointer in this situation anyway, so just remove it to make GCC
happy.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/lib/str_error_r.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/str_error_r.c b/tools/lib/str_error_r.c
index d6d65537b0d9..6aad8308a0ac 100644
--- a/tools/lib/str_error_r.c
+++ b/tools/lib/str_error_r.c
@@ -22,6 +22,6 @@ char *str_error_r(int errnum, char *buf, size_t buflen)
 {
 	int err = strerror_r(errnum, buf, buflen);
 	if (err)
-		snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
+		snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, [buf], %zd)=%d", errnum, buflen, err);
 	return buf;
 }
-- 
2.14.3