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From: Ian Lance Taylor <iant@google.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaud Lacombe <lacombar@gmail.com>, gcc-help@gcc.gnu.org,
        stufever@gmail.com, linux-kernel@vger.kernel.org,
        Wang Shaoyan <wangshaoyan.pt@taobao.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH] TRACING: Fix a copmile warning
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Date: Mon, 25 Jul 2011 17:44:25 -0700
In-Reply-To: <1311640534.3526.50.camel@gandalf.stny.rr.com> (Steven Rostedt's
	message of "Mon, 25 Jul 2011 20:35:34 -0400")
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Steven Rostedt <rostedt@goodmis.org> writes:

>> It seems gcc transforms the conditional from:
>> 
>> if (a != NULL && b != NULL) ...
>> 
>> to
>> 
>> if (b != NULL && a != NULL) ...
>> 
>> In which case the warning is fully valid. I'm not sure what's the C
>> standard guarantee in term of conditional test order. gcc 4.7.0 has
>> the same behavior.
>
> Yes it seems to be doing this :-/
>
> This is a real bug!

To be clear, gcc is not doing that, and this is not a code generation
bug.  It is a warning generation bug; the generated code is correct.

Ian