linux-kernel - [PATCH v3 2/2] auxdisplay: panel: avoid gcc 8's Wstringop-truncation warning

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Message-ID: <20180814193826.GA5459@gmail.com>
Date:   Tue, 14 Aug 2018 21:38:26 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Willy Tarreau <w@....eu>, Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Will Deacon <will.deacon@....com>,
        David Rientjes <rientjes@...gle.com>,
        Martin Sebor <msebor@...il.com>, Arnd Bergmann <arnd@...db.de>,
        Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v3 2/2] auxdisplay: panel: avoid gcc 8's Wstringop-truncation
 warning

Let gcc know it is not meant to be NUL-terminated by annotating with
the new __nonstring variable attribute; and remove the comment since it
conveys the same information.

Cc: Willy Tarreau <w@....eu>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Will Deacon <will.deacon@....com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Martin Sebor <msebor@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Joe Perches <joe@...ches.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
---
v3:
  Moved #ifdef block to the bottom of the file as suggested
  by Joe. Updated description of the nonstring attribute
  in the patch and in the commit message from the GCC docs.
  Put all Cc people in both patches since the second is
  really an example of the first. Added Linus and Greg.

v2:
  Re-sending this since a few months have passed, Martin has improved
  GCC's feature and warnings are appearing in Geert's build bot.
  Added an example in the second patch as requested by David.

 drivers/auxdisplay/panel.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c
index 3b25a643058c..21b9b2f2470a 100644
--- a/drivers/auxdisplay/panel.c
+++ b/drivers/auxdisplay/panel.c
@@ -155,10 +155,9 @@ struct logical_input {
 			int release_data;
 		} std;
 		struct {	/* valid when type == INPUT_TYPE_KBD */
-			/* strings can be non null-terminated */
-			char press_str[sizeof(void *) + sizeof(int)];
-			char repeat_str[sizeof(void *) + sizeof(int)];
-			char release_str[sizeof(void *) + sizeof(int)];
+			char press_str[sizeof(void *) + sizeof(int)] __nonstring;
+			char repeat_str[sizeof(void *) + sizeof(int)] __nonstring;
+			char release_str[sizeof(void *) + sizeof(int)] __nonstring;
 		} kbd;
 	} u;
 };
-- 
2.17.1