GNU bug report logs - #14565
24.3.50; Error with byte-compiled function using backward-char

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 14565 in the body.
You can then email your comments to 14565 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50; Error with byte-compiled function using backward-char
Date: Thu, 06 Jun 2013 16:24:17 +0200

When I evaluate and invoke each of the following functions, they both
work as expected:

(defun my-test-1 () (forward-char nil))

(defun my-test-2 () (backward-char nil))

But if I byte-compile them, only my-test-1 works; my-test-2 raises a
Lisp error: (wrong-type-argument number-or-marker-p nil)

Here are the byte codes:

(byte-code "\300\301\302\"\207" [defalias my-test-1 #[nil "\300u\207" [nil] 1]] 3)

(byte-code "\300\301\302\"\207" [defalias my-test-2 #[nil "\300[u\207" [nil] 1]] 3)

and here is the disassembled code:

byte code for my-test-1:
  args: nil
0	constant  nil
1	forward-char 
2	return	  

byte code for my-test-2:
  args: nil
0	constant  nil
1	negate	  
2	forward-char 
3	return	  


In GNU Emacs 24.3.50.1 (x86_64-suse-linux-gnu, GTK+ Version 3.4.4)
 of 2013-06-05 on rosalinde
Bzr revision: 112853 sdl.web <at> gmail.com-20130605074002-8mmjd1r5fvnb664v
Windowing system distributor `The X.Org Foundation', version 11.0.11203000
System Description:	openSUSE 12.2 (x86_64)

Configured using:
 `configure --without-toolkit-scroll-bars CFLAGS=-g3 -O0'

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Message #8 received at 14565 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: 14565 <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Thu, 06 Jun 2013 20:30:41 +0200

On Thu, 06 Jun 2013 16:24:17 +0200 Stephen Berman <stephen.berman <at> gmx.net> wrote:

> When I evaluate and invoke each of the following functions, they both
> work as expected:
>
> (defun my-test-1 () (forward-char nil))
>
> (defun my-test-2 () (backward-char nil))
>
> But if I byte-compile them, only my-test-1 works; my-test-2 raises a
> Lisp error: (wrong-type-argument number-or-marker-p nil)
>
> Here are the byte codes:
>
> (byte-code "\300\301\302\"\207" [defalias my-test-1 #[nil "\300u\207" [nil] 1]] 3)
>
> (byte-code "\300\301\302\"\207" [defalias my-test-2 #[nil "\300[u\207" [nil] 1]] 3)
>
> and here is the disassembled code:
>
> byte code for my-test-1:
>   args: nil
> 0	constant  nil
> 1	forward-char 
> 2	return	  
>
> byte code for my-test-2:
>   args: nil
> 0	constant  nil
> 1	negate	  
> 2	forward-char 
> 3	return	  

If `negate' in the byte code corresponds to the case Bnegate in
exec_byte_code, then IIUC nil fails the test for INTEGERP so is passed
to Fminus, and from there to arith_driver, where it fails
CHECK_NUMBER_OR_FLOAT_COERCE_MARKER, which via CHECK_TYPE signals the
wrong-type-argument error.  If this is what happens, then the byte code
of backward-char is at odds with its definition via move_point in
cmds.c, which explicitly checks whether the argument is nil, and if so
sets it to 1, which for Fbackward_char is then negated.  Or have I
completely misunderstood and if so, what is the error due to?

Steve Berman

Message #13 received at 14565-done <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 14565-done <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Thu, 06 Jun 2013 17:05:31 -0400

Version: 24.4

Thanks; fixed.

Message #16 received at 14565 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 14565 <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Thu, 06 Jun 2013 22:28:22 -0400

I suppose there could still be cases like

(setq foo nil)
(backward-char foo)

I wonder if these bytecomp handlers are worth keeping?

Message #19 received at 14565 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 14565 <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Fri, 07 Jun 2013 11:40:23 +0200

On Thu, 06 Jun 2013 22:28:22 -0400 Glenn Morris <rgm <at> gnu.org> wrote:

> I suppose there could still be cases like
>
> (setq foo nil)
> (backward-char foo)

Yes, in fact, after seeing your fix, I realized that I had
oversimplified my test case; the code which revealed the bug actually
looks more like this (still simplified, but enough to raise the error
with your fix):

(defun my-test-3 ()
  (let (x)
    (backward-char (when x 2))))

> I wonder if these bytecomp handlers are worth keeping?

I don't see how to tweak byte-compile-backward-char to account for the
above cases, but I don't understand the bytecomp code well.  However, I
did test adding a case Bbackward_char to exec_byte_code parallel to
Bforward_char, and that handles the above cases as expected.  So that
may be the easiest fix.

Steve Berman

Message #22 received at 14565 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 14565 <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Sat, 08 Jun 2013 15:20:20 +0200

On Fri, 07 Jun 2013 11:40:23 +0200 Stephen Berman <stephen.berman <at> gmx.net> wrote:

> On Thu, 06 Jun 2013 22:28:22 -0400 Glenn Morris <rgm <at> gnu.org> wrote:
>
>> I suppose there could still be cases like
>>
>> (setq foo nil)
>> (backward-char foo)
>
> Yes, in fact, after seeing your fix, I realized that I had
> oversimplified my test case; the code which revealed the bug actually
> looks more like this (still simplified, but enough to raise the error
> with your fix):
>
> (defun my-test-3 ()
>   (let (x)
>     (backward-char (when x 2))))
>
>> I wonder if these bytecomp handlers are worth keeping?
>
> I don't see how to tweak byte-compile-backward-char to account for the
> above cases, but I don't understand the bytecomp code well.  However, I
> did test adding a case Bbackward_char to exec_byte_code parallel to
> Bforward_char, and that handles the above cases as expected.  So that
> may be the easiest fix.

Should this bug be reopened, or would you prefer me to submit a new
report for the unresolved cases?

Steve Berman

Message #25 received at 14565 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 14565 <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Sat, 08 Jun 2013 15:46:42 +0200

On Sat, 08 Jun 2013 15:20:20 +0200 Stephen Berman <stephen.berman <at> gmx.net> wrote:

> On Fri, 07 Jun 2013 11:40:23 +0200 Stephen Berman <stephen.berman <at> gmx.net> wrote:
>
>> On Thu, 06 Jun 2013 22:28:22 -0400 Glenn Morris <rgm <at> gnu.org> wrote:
>>
>>> I suppose there could still be cases like
>>>
>>> (setq foo nil)
>>> (backward-char foo)
>>
>> Yes, in fact, after seeing your fix, I realized that I had
>> oversimplified my test case; the code which revealed the bug actually
>> looks more like this (still simplified, but enough to raise the error
>> with your fix):
>>
>> (defun my-test-3 ()
>>   (let (x)
>>     (backward-char (when x 2))))
>>
>>> I wonder if these bytecomp handlers are worth keeping?
>>
>> I don't see how to tweak byte-compile-backward-char to account for the
>> above cases, but I don't understand the bytecomp code well.  However, I
>> did test adding a case Bbackward_char to exec_byte_code parallel to
>> Bforward_char, and that handles the above cases as expected.  So that
>> may be the easiest fix.
>
> Should this bug be reopened, or would you prefer me to submit a new
> report for the unresolved cases?

I just saw that you already took care of these cases; thanks.

Steve Berman

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.