GNU bug report logs - #8545
issues with recent doprnt-related changes

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From: Jason Rumney <jasonr <at> gnu.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: lekktu <at> gmail.com, 8545 <at> debbugs.gnu.org, rms <at> gnu.org
Subject: bug#8545: issues with recent doprnt-related changes
Date: Sun, 01 May 2011 12:25:45 +0800

Paul Eggert <eggert <at> cs.ucla.edu> writes:

> On 04/29/11 05:28, Richard Stallman wrote:
>
>> We are concerned with standards insofar as they matter in practice
>> for the convenience and reliability of our software.
>
> Yes, of course, I should have made that clearer.  Standards are our
> tools, not our masters.
>
>>> If you assign i = INT_MAX + 1, the resulting behavior is undefined.
>>
>> The result is INT_MIN.  We don't try to support any theoretical machine
>> where this would not be so.
>
>    long
>    foo (char *p, int i)
>    {
>      return &p[i + 1] - &p[i];
>    }
>
> On typical hosts where int is 32 bits, and long and char * are
> both 64 bits, most compilers optimize that "return" statement
> to "return 1;", even when I is INT_MAX and I + 1 therefore
> overflows.

That does not mean that INT_MAX + 1 is undefined.  You are also
involving implicit casts here. Exactly where those casts happen is what
is undefined.

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