From bug-request at octave dot org Tue Jan 11 03:15:53 2005
Subject: Re: Segmentation fault?
From: David Bateman <David dot Bateman at motorola dot com>
To: Vic Norton <vic at norton dot name>
Cc: Per Persson <persquare at mac dot com>, bug@octave.org
Date: Tue, 11 Jan 2005 10:16:09 +0100

Daprès Vic Norton <vic at norton dot name> (le 10/01/2005):
> I got gbd working, David. I hadn't put in the appropriate path. I got 
> pretty much the same thing Per reported:
>    (gdb) run
>    Starting program: /opt/local/bin/octave
>    ...
>    octave> rrtest1D
>    octave> clear all
>    octave> quit
>   
>    Program received signal EXC_BAD_ACCESS, Could not access memory.
>    __tcf_0 () at oct-obj.h:153
>    153     oct-obj.h: No such file or directory.
>            in oct-obj.h
>    (gdb) bt
>    #0  __tcf_0 () at oct-obj.h:153
>    Cannot access memory at address 0x4146870
>    #1  0x9002c7b8 in exit ()
>    #2  0x04919874 in clean_up_and_exit(int) (retval=-1610579852) at 
> toplev.cc:227
>    ...
>    #11 0x000025d4 in _start (argc=1, argv=0xbffffd9c, 
> envp=0xbffffda4) at /SourceCache/Csu/Csu-46/crt.c:267
>    #12 0x00002448 in start ()
>    Current language:  auto; currently c++
> 
> Without the "clear all" line there is no problem.
> 
> Thanks for your help, David. And thank you too, Per.

Vic,

So you have exactly the same problem as Per.... The code causing the problem
is

class
octave_value_list
{
public:
  ...
  octave_value& elem (int n)
    {
      static Matrix empty_matrix;

      if (n >= length ())
        resize (n+1, empty_matrix);

      return data[n];
    }
  ...
};

where the empty_matrix is cast as an octave_value and then resize is

void
octave_value_list::resize (int n, const octave_value& val)
{
  int len = length ();

  if (n > len)
    {
      data.resize (n);

      for (int i = len; i < n; i++)
        data[i] = val;
    }
  else if (n < len)
    data.resize (n);
}

line 153 itself in 2.1.64 is "static Matrix empty_matrix;". So it is a bit
wierd to me that empty_matrix doesn't exist for you. An easy fix for this,
that will be slightly less efficient would be to just delete the "static"
keyword on line 153.

Regards
David

-- 
David Bateman                                David dot Bateman at motorola dot com
Motorola CRM                                 +33 1 69 35 48 04 (Ph) 
Parc Les Algorithmes, Commune de St Aubin    +33 1 69 35 77 01 (Fax) 
91193 Gif-Sur-Yvette FRANCE

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