From: Aidan Kehoe <kehoea@parhasard.net>
To: Reiner Steib <Reiner.Steib@gmx.de>
Cc: xemacs-patches@xemacs.org, ding@gnus.org
Subject: Re: [PATCH] Fix a bug with XEmacs and bignum support.
Date: Sun, 11 Jan 2009 21:57:02 +0000 [thread overview]
Message-ID: <18794.27438.538380.420833@parhasard.net> (raw)
In-Reply-To: <878wphpxuw.fsf@marauder.physik.uni-ulm.de>
Ar an t-aonú lá déag de mí Eanair, scríobh Reiner Steib:
> If you need to make sure that the correct runtime value is used, I
> don't understand why you hard-code 134217727? I would have
> expected...
>
> (minid (or (and (boundp 'most-positive-fixnum)
> most-positive-fixnum)
> (lsh -1 -1)))
>
> What am I missing?
Nothing, that’s a perfectly reasonable approach too.
> On a 64-bit machine, I get:
>
> ,----[ M-x ielm RET ]
> | ELISP> (lsh -1 -1)
> | 576460752303423487
> | ELISP> (emacs-version)
> | "GNU Emacs 21.3.1 (x86_64-suse-linux, X toolkit, Xaw3d scroll bars)\n of 2004-1\
> | 0-05 on prokofjieff"
> | ELISP> (when (require 'cl) most-positive-fixnum)
> | 576460752303423487
> `----
>
> When I used this machine(s) some years ago, I always compiled Gnus,
> AUCTeX, BBDB, emacs-w3m, etc on a 64-bit machine and ran the compiled
> Lisp code on both, 64-bit and 32-bit machines
> (/usr/local/share/emacs/site-lisp shared via NFS).
I don’t know if the bug will actually produce noticeable symptoms in
practice--I was curious where the technique had been used, and I found the
code via this search:
http://www.google.com/codesearch?q=lsh\+-1\+-1+file%3A\.el
I haven’t been bitten by the bug.
GNU Emacs certainly does silently overflow, though, writing out a 59-bit
number into byte-compiled code can provoke bugs if that code is run on a
machine where a Lisp integer is 28 bits wide. But you won’t get a
wrong-type-argument or anything of the sort, unless the sign is explicitly
checked.
--
¿Dónde estará ahora mi sobrino Yoghurtu Nghe, que tuvo que huir
precipitadamente de la aldea por culpa de la escasez de rinocerontes?
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next prev parent reply other threads:[~2009-01-11 21:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <18793.58572.280122.113699@parhasard.net>
2009-01-11 15:20 ` Reiner Steib
2009-01-11 15:55 ` Aidan Kehoe
2009-01-11 17:16 ` Reiner Steib
2009-01-11 21:57 ` Aidan Kehoe [this message]
2009-01-12 22:45 ` Katsumi Yamaoka
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