[Pkg-octave-devel] Bug#485920: [patch] Re: waitbar() crashing when used from within emacs

[Thomas Weber <thomas.weber.mail@gmail.com>]

On 20/06/08 10:17 -0500, Quentin Spencer wrote:
> Thomas Weber wrote:
>> Am Donnerstag, den 12.06.2008, 12:44 +0200 schrieb Thomas Weber:
>>   
>>> Hi, 
>>>
>>> starting an octave-inferior process within Emacs and then using the
>>> waitbar function from miscellaneous crashes octave:
>>>
>>> octave> waitbar(0)
>>> panic: Segmentation fault -- stopping myself...
>>> attempting to save variables to `octave-core'...
>>> save to `octave-core' complete
>>>
>>> Process Inferior Octave segmentation fault
>>>
>>>
>>> The crash happens in line 150 where buf_ptr is a null pointer. The
>>> problematic part is however in line 147 already, where tgetstr() returns
>>> 0. Excerpt from tgetstr()'s man page:
>>>
>>> "The tgetstr routine returns the string entry for id, or zero if it is
>>> not available."
>>>
>>> I don't know if it's possible to change waitbar() to work from within
>>> Emacs.
>>>
>>> 	Thomas
>>>     
>
>
> It has been a long time since I wrote this. If I recall correctly, the  
> purpose of this was to get the width of the terminal, which apparently  
> does not work inside emacs. The fix is probably to deal with zero output  
> correctly, probably just forcing it to use the parts of the code where  
> it defaults to some fixed width if it can't figure out how wide it  
> should be.

I took a closer look at the code. The part in question implements a progress
bar by switching into standout mode (tgetstr("so", &buf_ptr);) and back out
from standout mode (tgetstr("se", &buf_ptr);)

Emacs doesn't seem to handle this, but as there is a progress reporter in
percent, the attached patch simply protects the null pointer dereference (the
patch looks bigger than it is, as I adjusted the indendation accordinly).

	Thomas

Index: main/miscellaneous/src/waitbar.cc
===================================================================
--- main/miscellaneous/src/waitbar.cc	(revision 5132)
+++ main/miscellaneous/src/waitbar.cc	(working copy)
@@ -146,11 +146,18 @@
 	  char* buf_ptr	= term_buffer;
 	  begin_rv	= tgetstr("so", &buf_ptr);
 	  end_rv	= tgetstr("se", &buf_ptr);
-	  brvlen = 0;	buf_ptr = begin_rv;
-	  while(buf_ptr[++brvlen]);
-	  ervlen = 0;	buf_ptr = end_rv;
-	  while(buf_ptr[++ervlen]);
 	  
+	  // Display a progress bar, but only if the current terminal has a
+	  // standout mode
+	  if (begin_rv && end_rv)
+	    {
+	      brvlen = 0;	
+	      buf_ptr = begin_rv;
+	      while(buf_ptr[++brvlen]);
+	      ervlen = 0;	buf_ptr = end_rv;
+	      while(buf_ptr[++ervlen]);
+	    }
+	 	  
 	  // initialize print buffer
 	  for(i=0; i<BUF_SIZE; ++i)
 	    print_buf[i]	= ' ';