GNU bug report logs - #2790
emacs 22.1.1 cannot open 5GB file on 64GB 64-bit Linux box

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Andreas Schwab <schwab <at> linux-m68k.org>
Cc: 2790 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>,
        tutufan <at> gmail.com
Subject: bug#2790: emacs 22.1.1 cannot open 5GB file on 64GB 64-bit	GNU/Linux box
Date: Sun, 29 Mar 2009 20:59:09 -0400

>> In that case I'd rather do the check more directly, e.g.:
>> (((EMACS_INT)st.st_size)*4)/4 == st.st_size
> That will reintroduce the buggy reliance on undefined integer overflow.

I do not know what you're referring to.  If you're referring to the fact
that (((EMACS_INT)st.st_size)*4) may overflow, then I'm not sure what
problem you're envisaging: do you think that in some cases where it
overflows, (((EMACS_INT)st.st_size)*4)/4 may still be equal to
st.st_size (I can't think of any meningful semantics for overflow that
would give me that property)?  Or are you concerned about trapping
overflow semantics (I've never seen it in use and doubt Emacs would
work in such a system)?


        Stefan

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