From: Eli Zaretskii <eliz@gnu.org>
To: Robert Pluim <rpluim@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Floating-point constant folding in Emacs byte compiler
Date: Mon, 26 Mar 2018 19:02:54 +0300 [thread overview]
Message-ID: <838taeg6z5.fsf@gnu.org> (raw)
In-Reply-To: <87370m3k4y.fsf@gmail.com> (message from Robert Pluim on Mon, 26 Mar 2018 17:57:01 +0200)
> From: Robert Pluim <rpluim@gmail.com>
> Cc: emacs-devel@gnu.org
> Date: Mon, 26 Mar 2018 17:57:01 +0200
>
> >> >> I imagine that on a 32-bit version of emacs, (byte-compile (lambda (x)
> >> >> (* #x10000 #x10000))) similarly produces a constant-zero function,
> >> >
> >> > The result depends on whether Emacs was build --with-wide-int. If it
> >> > was, the result is #[(x) "\300\207" [4294967296] 1], if it wasn't, I
> >> > get #[(x) "\300\207" [0] 1].
> >>
> >> Hmm, would it be worthwhile to have Emacs signal overflow in such a
> >> situation (perhaps controlled by a configuration variable) so we could
> >> fix such issues?
> >
> > In which of these two cases do you see overflow?
> >
>
> Does (* #x10000 #x10000) not overflow on 32-bit?
Only if Emacs was not built --with-wide-int.
> > I also don't think I understand the utility of signaling an overflow
> > error from the byte compiler that happened because it did constant
> > folding. What else except bug reports could this yield?
>
> I was proposing it as a debug option, not a generally enabled one. Of
> course if there's no overflow, it would be kind of useless :-)
If we want the byte code to be portable, the results of compiling
cannot depend on the machine on which the code was byte-compiled.
next prev parent reply other threads:[~2018-03-26 16:02 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-22 23:04 Floating-point constant folding in Emacs byte compiler Paul Eggert
2018-03-23 1:26 ` Stefan Monnier
2018-03-23 5:22 ` Paul Eggert
2018-03-23 8:24 ` Eli Zaretskii
2018-03-23 20:00 ` Paul Eggert
2018-03-23 8:15 ` Eli Zaretskii
2018-03-23 20:52 ` Pip Cet
2018-03-24 6:25 ` Eli Zaretskii
2018-03-26 9:39 ` Robert Pluim
2018-03-26 15:13 ` Eli Zaretskii
2018-03-26 15:57 ` Robert Pluim
2018-03-26 16:02 ` Eli Zaretskii [this message]
2018-03-26 18:23 ` Pip Cet
2018-03-26 18:29 ` Eli Zaretskii
2018-03-27 0:28 ` Paul Eggert
2018-03-27 23:28 ` Paul Eggert
2018-03-30 16:26 ` Pip Cet
2018-03-30 16:31 ` Noam Postavsky
2018-03-30 16:39 ` Paul Eggert
2018-04-02 10:56 ` Pip Cet
2018-04-02 11:22 ` Eli Zaretskii
2018-04-02 11:42 ` Pip Cet
2018-04-02 12:50 ` Eli Zaretskii
2018-04-02 14:50 ` Stefan Monnier
2018-04-02 15:02 ` Pip Cet
2018-04-02 12:57 ` Noam Postavsky
2018-04-02 13:30 ` Eli Zaretskii
2018-04-02 14:48 ` Stefan Monnier
2018-04-02 19:20 ` Paul Eggert
2018-04-02 19:39 ` Pip Cet
2018-04-02 19:58 ` Eli Zaretskii
2018-04-02 20:55 ` Pip Cet
[not found] ` <<83y3i568i0.fsf@gnu.org>
2018-04-02 13:37 ` Drew Adams
2018-04-02 14:05 ` Eli Zaretskii
2018-04-02 14:54 ` Pip Cet
2018-04-02 15:02 ` Drew Adams
2018-03-26 17:52 ` Stefan Monnier
2018-03-26 18:30 ` Eli Zaretskii
2018-03-27 0:08 ` Paul Eggert
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