linux-kernel - Re: [PATCH] LLVMLinux: Remove warning about returning an uninitialized variable

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Message-ID: <5339E946.90903@converseincode.com>
Date:	Mon, 31 Mar 2014 15:16:38 -0700
From:	Behan Webster <behanw@...verseincode.com>
To:	"H. Peter Anvin" <hpa@...or.com>, arnd@...db.de
CC:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	dwmw2@...radead.org, pageexec@...email.hu,
	Mark Charlebois <charlebm@...il.com>
Subject: Re: [PATCH] LLVMLinux: Remove warning about returning an uninitialized
 variable

On 03/31/14 15:11, H. Peter Anvin wrote:
> On 03/31/2014 03:10 PM, Behan Webster wrote:
>>>> diff --git a/include/asm-generic/cmpxchg-local.h
>>>> b/include/asm-generic/cmpxchg-local.h
>>>> index d8d4c89..4c41bb8 100644
>>>> --- a/include/asm-generic/cmpxchg-local.h
>>>> +++ b/include/asm-generic/cmpxchg-local.h
>>>> @@ -41,6 +41,7 @@ static inline unsigned long
>>>> __cmpxchg_local_generic(volatile void *ptr,
>>>>            break;
>>>>        default:
>>>>            wrong_size_cmpxchg(ptr);
>>>> +        prev = 0;
>>>>        }
>>>>        raw_local_irq_restore(flags);
>>>>        return prev;
>>>>
>>> Shouldn't this be a build time assert (__compiletime_error())?
>> I changed it to a __noreturn on wrong_size_cmpxchg thanks to James
>> Bottomley.
>>
>> Which would be better?
>>
> __compiletime_error traps at compile time rather than link time, which
> is what you want.
The idea is to remove the compile time warning that the return code 
"prev" isn't initialized in the default case. Indicating that 
wrong_size_cmpxchg doesn't return fixes that false positive.

Behan

-- 
Behan Webster
behanw@...verseincode.com

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