linux-kernel - Re: [Bulk] Re: [PATCH 4/10] compiler-gcc{3,4}.h: Use GCC

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Message-ID: <50664179.5090608@att.net>
Date:	Fri, 28 Sep 2012 19:31:53 -0500
From:	Daniel Santos <danielfsantos@....net>
To:	Josh Triplett <josh@...htriplett.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christopher Li <sparse@...isli.org>,
	David Daney <david.daney@...ium.com>,
	David Howells <dhowells@...hat.com>,
	Joe Perches <joe@...ches.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	linux-sparse@...r.kernel.org,
	Michel Lespinasse <walken@...gle.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Pavel Pisa <pisa@....felk.cvut.cz>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [Bulk] Re: [PATCH 4/10] compiler-gcc{3,4}.h: Use GCC_VERSION
 macro

On 09/28/2012 07:20 PM, Josh Triplett wrote:
> On Fri, Sep 28, 2012 at 06:20:05PM -0500, Daniel Santos wrote:
>> --- a/include/linux/compiler-gcc4.h
>> +++ b/include/linux/compiler-gcc4.h
>> @@ -13,11 +13,11 @@
>>  #define __must_check 		__attribute__((warn_unused_result))
>>  #define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
>>  
>> -#if __GNUC_MINOR__ > 0
>> +#if GCC_VERSION >= 40102
>>  # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
>>  #endif
> You've changed the semantics of this one; if literally translated, this
> should have become #if GCC_VERSION >= 40100.  If you intended to change
> that, could you please document why?  And in any case, could you make
> that semantic change in a separate commit from the switch to
> GCC_VERSION?
hmm, it looks like somebody commented out the #error that would normally
prevent that test from ever occurring on 4.1.0 or 4.1.1.
When I had written this patch, it wasn't commented out and I had assumed
that it was obvious from the context.
>  /* GCC 4.1.[01] miscompiles __weak */
>  #ifdef __KERNEL__
> -# if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
> +# if GCC_VERSION >= 40100 &&  GCC_VERSION <= 40101
>  //#  error Your version of gcc miscompiles the __weak directive
>  # endif
>  #endif
> @@ -13,11 +13,11 @@
>  #define __must_check 		__attribute__((warn_unused_result))
>  #define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
>  
> -#if __GNUC_MINOR__ > 0
> +#if GCC_VERSION >= 40102
>  # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
>  #endif
I would say that commenting this out is bad if __weak is miscompiled. 
If we don't want to break the build, should we at least be defining
__weak to something else?

Daniel
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