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Re: svn commit: r38193 - trunk/subversion/libsvn_subr

From: Philip Martin <philip_at_codematters.co.uk>
Date: Thu, 25 Jun 2009 20:18:05 +0100

Stefan Sperling <stsp_at_elego.de> writes:

> He also says you cannot reliably subtract two unsinged numbers
> from one another. But the same holds for signed values. Both can
> wrap around.

In C they are different. Unsigned integer overflow is OK, it has
defined behaviour but signed integer overflow is undefined. Yes, on
most platforms signed integer overflow is perfectly predictable two's
complement, however optimising compilers may assume that it doesn't
happen which can surprise the unwary (that's why gcc has options like
-fstrict-overflow and -fwrapv).

Received on 2009-06-25 21:18:26 CEST

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