bug#1380: 23.0.60; file content causes CVS emacs to crash

[Chong Yidong <cyd@stupidchicken.com>]

> The file content in a file causes Emacs to crash as soon as it's
> opened.  Tested with "emacs -q file".

Looks like the charbuf in the coding structure is overflowing.  The
following rough patch prevents this overflow and the crash, but maybe
there is a deeper bug.  The comments in coding.c:6610 says "We are sure
that the number of data is less than the size of coding->charbuf."  This
bug comes about due to that faile assumption.

Handa-san, what do you think?

*** trunk/src/coding.c.~1.394.~	2008-10-24 00:06:43.000000000 -0400
--- trunk/src/coding.c	2008-11-20 02:29:02.000000000 -0500
***************
*** 6617,6622 ****
--- 6617,6633 ----
  
  	      if (c & 0x80)
  		c = BYTE8_TO_CHAR (c);
+ 
+ 	      if (coding->charbuf_used >= coding->charbuf_size)
+ 		{
+ 		  int *old_charbuf = coding->charbuf;
+ 
+ 		  coding->charbuf_size *= 2;
+ 		  coding->charbuf = (int *) alloca (sizeof (int)
+ 						    * coding->charbuf_size);
+ 		  bcopy (old_charbuf, coding->charbuf, coding->charbuf_size);
+ 		}
+ 
  	      coding->charbuf[coding->charbuf_used++] = c;
  	    }
  	  produce_chars (coding, Qnil, 1);