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

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Message #108 received at 8545 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Jason Rumney <jasonr <at> gnu.org>
Cc: lekktu <at> gmail.com, 8545 <at> debbugs.gnu.org, rms <at> gnu.org
Subject: Re: bug#8545: issues with recent doprnt-related changes
Date: Sat, 30 Apr 2011 22:56:45 -0700

On 04/30/11 21:25, Jason Rumney wrote:
> You are also
> involving implicit casts here. Exactly where those casts happen is what
> is undefined.

I'm not sure what is meant here, as the program in question
doesn't have any implicit arithmetic conversions (or at least,
it doesn't on the typical 64-bit host I was talking about).

> That does not mean that INT_MAX + 1 is undefined.

It could well be that the exact expression "INT_MAX + 1"
has well-defined behavior on all platforms we care about,
and that it always returns INT_MIN.  But I'm concerned
about the more general issue, which is whether Emacs code
can always assume that signed integer arithmetic
wraps around.  Unfortunately, there are many practical
Emacs targets where it's incorrect to assume that.

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