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From: | Paolo Bonzini |
Subject: | Re: GCC optimizes integer overflow: bug or feature? |
Date: | Tue, 19 Dec 2006 11:37:34 +0100 |
User-agent: | Thunderbird 1.5.0.8 (Macintosh/20061025) |
By the way, as I've tried to describe here: <http://cert.uni-stuttgart.de/advisories/c-integer-overflow.php> variable range tracking can result in reintroduction of supposedly-fixed security vulnerabilities. 8-(
Interesting read. I agree with the proposed fix; however, note that GCC does not make the result of overflowing signed left-shifts undefined, exactly because in this case the overflow is relied upon by too many existing programs (and also because left shifts are inherently a bitwise operation, with well defined overflowing behavior on the most significant bits).
Paolo
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