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Re: Integer wraparound bug with eval on OS X
From: |
Eric Blake |
Subject: |
Re: Integer wraparound bug with eval on OS X |
Date: |
Tue, 01 May 2007 06:48:03 -0600 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.10) Gecko/20070221 Thunderbird/1.5.0.10 Mnenhy/0.7.5.666 |
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According to Gary V. Vaughan on 4/30/2007 10:49 AM:
> Hi Eric,
>
> I think your recent patch to eval has either broken something, or else
> tickled a long standing bug. Using the latest gnulib and m4 HEAD, test
> 135 is failing.
> eval(-4 >> 65)
> -1
> eval(-4 >> 64)
> -1
> eval(-4 >> 63)
> -1
It looks like the failure is due to undefined C code (shifting by an
amount larger than the width of the type), and that the testsuite is just
tickling a long-standing bug. branch-1_4 is immune because it
intentionally masks the shift amount to bring it back into width, so I
will have to port some of that code to HEAD. Thanks for the heads-up on this.
- --
Don't work too hard, make some time for fun as well!
Eric Blake address@hidden
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- Re: Integer wraparound bug with eval on OS X,
Eric Blake <=