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

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Message-ID: <5339D57A.4050504@zytor.com>
Date:	Mon, 31 Mar 2014 13:52:10 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	behanw@...verseincode.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 03/21/2014 11:38 PM, behanw@...verseincode.com wrote:
> From: Behan Webster <behanw@...verseincode.com>
> 
> Fix uninitialized return code in default case in cmpxchg-local.h
> 
> This patch fixes the code to prevent an uninitialized return value that is detected
> when compiling with clang. The bug produces numerous warnings when compiling the
> Linux kernel with clang.
> 
> Signed-off-by: Behan Webster <behanw@...verseincode.com>
> Signed-off-by: Mark Charlebois <charlebm@...il.com>
> ---
>  include/asm-generic/cmpxchg-local.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> 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())?

	-hpa

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