Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753495Ab3ISTNZ (ORCPT ); Thu, 19 Sep 2013 15:13:25 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39619 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753199Ab3ISTNY (ORCPT ); Thu, 19 Sep 2013 15:13:24 -0400 Date: Thu, 19 Sep 2013 15:13:15 -0400 From: Benjamin Poirier To: "Yann E. MORIN" Cc: Madhavan Srinivasan , mmarek@suse.cz, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH]kconfig/menu.c: fix uninitialized variable warning Message-ID: <20130919191315.GA19703@d2.synalogic.ca> References: <1379575697-6740-1-git-send-email-maddy@linux.vnet.ibm.com> <20130919152227.GB19364@d2.synalogic.ca> <20130919172751.GA3317@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20130919172751.GA3317@free.fr> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3553 Lines: 92 On 2013/09/19 19:27, Yann E. MORIN wrote: > Benjamin, Madhavan, All, > > On 2013-09-19 11:22 -0400, Benjamin Poirier spake thusly: > > On 2013/09/19 12:58, Madhavan Srinivasan wrote: > > > In file included from scripts/kconfig/zconf.tab.c:2537:0: > > > scripts/kconfig/menu.c: In function ‘get_symbol_str’: > > > scripts/kconfig/menu.c:586:18: warning: ‘jump’ may be used uninitialized in > > > this function [-Wmaybe-uninitialized] > > ^^^^^ > > > > from gcc(1): > > "These warnings are made optional because GCC is not smart > > enough to see all the reasons why the code might be correct > > despite appearing to have an error." > > > > I do not see this warning with gcc 4.7.2 or 4.8.1. Which version are you > > using? > > > > The code does: > > > > static void get_prompt_str(struct gstr *r, struct property *prop, > > [...] > > if (head && location) { > > jump = xmalloc(sizeof(struct jump_key)); > > [... different basic block ...] > > if (head && location && menu == location) > > jump->offset = r->len - 1; > > > > If the second "if" is true, then the first one was true as well, and > > "jump" is initilized. > > Exactly what I was going to say. > > However: > - I believe we should strive for a warning-free code whenever possible > - while still getting help from gcc to pinpoint potential issues. > > Clearly, gcc is wrong here. Setting jump to NULL will cause fault if we > try to dereference it. Since this should never happen given the code as > it currently is, I'm slightly in favour of acking this patch. > > Any other reason not to apply it? Did you manage to get that warning as well? I didn't. If it's only from old versions of gcc I'd feel better leaving the warning there than masking it, in case a future code change does really introduce a use before initialize. > > > > jump->offset = r->len - 1; > > > ^ > > > scripts/kconfig/menu.c:547:19: note: ‘jump’ was declared here > > > struct jump_key *jump; > > > ^ > > > Signed-off-by: Madhavan Srinivasan > > > --- > > > scripts/kconfig/menu.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c > > > index c1d5320..23b1827 100644 > > > --- a/scripts/kconfig/menu.c > > > +++ b/scripts/kconfig/menu.c > > > @@ -544,7 +544,7 @@ static void get_prompt_str(struct gstr *r, struct property *prop, > > > { > > > int i, j; > > > struct menu *submenu[8], *menu, *location = NULL; > > > - struct jump_key *jump; > > > + struct jump_key *jump = NULL; > > > > > > str_printf(r, _("Prompt: %s\n"), _(prop->text)); > > > menu = prop->menu->parent; > > > -- > > > 1.7.10.4 > > > > > Regards, > Yann E. MORIN. > > -- > .-----------------.--------------------.------------------.--------------------. > | Yann E. MORIN | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: | > | +33 662 376 056 | Software Designer | \ / CAMPAIGN | ___ | > | +33 223 225 172 `------------.-------: X AGAINST | \e/ There is no | > | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL | v conspiracy. | > '------------------------------^-------^------------------^--------------------' -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/