Possible (new) sscanf bug

[Charles Wilson <cwilson@ece.gatech.edu>]

This report is from Ben Wing on the XEmacs-nt mailing list.  Given his 
track record, if Ben thinks there's a bug in sscanf, there probably is. 
  I don't have a self-contained test case (but I'll try to gen one soon) 
-- but I did want to put this report "in the record".

I'm not going to have much time to track this down until the weekend; 
anybody who wants to take a look at it before then is more than welcome. :-)

--Chuck

Ben Wing wrote:

> i'm using 1.3.2.
> 
> i still wonder though whether i'm not seeing a sscanf bug, as i get a crash on a
> line with sscanf in it, and my char * pointer is getting corrupted [set to a
> small number] -- and it occurs on the stack, directly above the last variable
> that sscanf is supposed to be writing into.
> 
> here's the code:
> 
>       char *p = line;
>       int cp1, cp2, endcount;
>       int cp1high, cp1low;
>       int dummy;
> 
>       while (*p) /* erase all comments out of the line */
> 	{
> 	  if (*p == '#')
> 	    *p = '\0';
> 	  else
> 	    p++;
> 	}
>       /* see if line is nothing but whitespace and skip if so */
>       p = line + strspn (line, " \t\n\r\f");
>       if (!*p)
> 	continue;
>       if ((!ignore_first_column ?      <-------------------------------------
> 	   sscanf (p, "%i %i %n", &cp1, &cp2, &endcount) < 2 :
> 	   sscanf (p, "%i %i %i %n", &dummy, &cp1, &cp2, &endcount) < 3)
> 	  || *(line + endcount))
> 	{
> 	  warn_when_safe (intern ("unicode"), Qnotice,
> 			  "Unrecognized line in translation file %s:\n%s",
> 			  XSTRING_DATA (filename), line);
> 	  continue;
> 	}
>       if (cp1 >= st && cp1 <= en)
> 
> 
> GDB reports the crash on the line indicated, and reports p as 0x24 <address out
> of bounds>.
> 
> are you in contact with cygwin people?
> 
> 
> Charles Wilson wrote:
> 
>> 
>> Ben Wing wrote:
>> 
> 
>> > One problem I've
>> > noticed so far is with Cygwin w/Mule: you get a crash at startup in
>> > parse-unicode-translation-table.  I don't quite know what the problem is and
>> > haven't been able to debug it yet, as the debugger keeps locking up.  MS Win
>> > does the same code, though, without problems, so it almost looks like either a
>> > GCC bug or a bug in sscanf[].
> 
>> 
>> Which cygwin kernel are you using in your tests, Ben?
>> cygwin-1.3.0/1.3.1 had a significant bug in sscanf, but it was fixed by
>> 1.3.2.
>> 
>> --Chuck
> 



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