linux-kernel - Re: [PATCH] [PERF] (Userspace Tools) Fix a compilation error with -fstack-protector and -Werror

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Message-ID: <AANLkTikAU+JdTLJqCnG_bdUqLLtvCdXGYymJ6ePapq1Y@mail.gmail.com>
Date:	Tue, 19 Oct 2010 14:37:31 +0300
From:	Brian Gitonga Marete <marete@...hnix.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] [PERF] (Userspace Tools) Fix a compilation error with
 -fstack-protector and -Werror

On Tue, Oct 19, 2010 at 2:33 PM, Brian Gitonga Marete
<marete@...hnix.com> wrote:
> On Tue, Oct 19, 2010 at 2:12 PM, Brian Gitonga Marete
> <marete@...hnix.com> wrote:
>> On Tue, Oct 19, 2010 at 9:40 AM, Ingo Molnar <mingo@...e.hu> wrote:
>>>
>>> * Brian Gitonga Marete <marete@...hnix.com> wrote:
>>>
>>>> On Tue, Oct 19, 2010 at 2:38 AM, Frederic Weisbecker <fweisbec@...il.com> wrote:
>>>> > On Tue, Oct 19, 2010 at 02:24:00AM +0300, Brian Gitonga Marete wrote:
>>>> >> The following patch fixes compilation of the perf user-space tools on,
>>>> >> for example, gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) . It should not
>>>> >> break anything else.
>>>> >
>>>> >
>>>> >
>>>> > Hi,
>>>> >
>>>> > What kind of warning have you encountered and why it fixes it?
>>>> > Can you describe that in your changelog?
>>>> >
>>>>
>>>> Hello Frederic,
>>>>
>>>> Some versions of gcc, e.g. gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4), have the
>>>> (default) minimum size of buffers protected by `-fstack-protector' set to 8. But
>>>> in perf, there exist much smaller automatic buffers.
>>>
>>> Hm, it's this code:
>>>
>>>        /* newtWinChoice should really be accepting const char pointers... */
>>>        char yes[] = "Yes", no[] = "No";
>>>        return newtWinChoice(NULL, yes, no, (char *)msg) == 1;
>>>
>>> I.e. the code is messy and GCC is right to warn about it. Hence it would be somewhat
>>> bad to actually remove the warning that pointed out some dodgy piece of code.
>>>
>>> Even if marking it const doesnt work due to the external libnewt API, we could at
>>> least put 'yes' and 'no' into file scope and mark them static?
>>
>> OK. Now that I actually look closely at that fragment I can see its
>> useless to create the automatic arrays. Local string literals would
>> also work (i.e. just pass `"Yes"' and `"No"' to newtWinChoice). But
>> can also do what you suggested if it is anticipated that they will be
>> used somewhere else within the file at some other time -- Currently
>> they are not.
>>
>
> Oops. Sorry. What I suggested won't work because of the
> -Wwrite-strings default option. Which actually makes me understand why
> the original author of the code made it the way it is. Your suggestion
> of file-scope, static does solve the problem.
>

As indeed does Americo's suggestion above.


-- 
Brian Gitonga Marete
Toshnix Systems
Tel: +254722151590
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