linux-kernel - Re: [ofa-general] Re: dealing with gcc 'comparison is always false' warnings

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Message-ID: <adaveeaqp8q.fsf@cisco.com>
Date:	Wed, 30 May 2007 08:56:37 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	"Satyam Sharma" <satyam.sharma@...il.com>
Cc:	linux-kernel@...r.kernel.org, openib-general@...nib.org
Subject: Re: [ofa-general] Re: dealing with gcc 'comparison is always false' warnings

 > However, gcc is _just as correct_. It is only crying about seeing a condition
 > that the programmer could have written with some purpose in mind but which
 > is being completely compiled away by it when generating the code because
 > of it being a tautology / contradiction ...

Well, OK, but there's lots of things gcc could warn about.  How about

	while (1) { ...

By your argument gcc should warn that '1' always evaluates to true.
Or how about

#if 0

why shouldn't the preprocessor warn that the conditional is always false?

 > No, shutting gcc up wouldn't be the right thing, IMHO. These warnings are
 > a good reminder to the programmer to go and see if there is a real bug
 > somewhere and if something really needs to be done with the code (could
 > be simply to change the type of a variable to signed that was mistakenly
 > declared unsigned, f.e.).

OK, but suppose I looked at it and there's no bug.  Leaving the
warning has a cost too: it hides useful warnings (that might be
showing real bugs) in all the clutter.

 - R.
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