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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/61131] [4.8 regression] ARM -Os: incorrect code generation
Date: Mon, 12 May 2014 16:22:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61131

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Stephen Warren from comment #3)
> This certainly violates the principle of least-surprise...
> 
> Once i==2, "p->fd[i] >= 0" is certainly undefined. Surely "undefined &&
> false" is false though, since "anything && false" is false; short-circuit
> evaluation should surely only apply if "anything" was known to be false, and
> presumably "undefined" isn't known to be false. Or is the definition of
> undefined such that it propagates through the entire expression irrespective
> of the expression's logic? I suppose that could be the case, but it's
> certainly not the most useful definition of undefined:-)

The undefined basically gets turned into a continue. Also the value is not just
undefined, the effect of doing an out of bounds is undefined and could even
crash.