patch for gas/dwarf2dbg.c, core dump and corrupted .debug_line section

[Jim Wilson <wilson@cygnus.com>]

This fixes 4 problems I noticed while trying to use this code from gcc.

1) The comments in get_filenum do not match the code.  The code is correct.
2) get_filenum performs an out-of-bounds array access if filenum is 0, which
   makes last == -1.
3) get_filenum does not update ls.last_filename when creating a new filetable
   entry.
4) dwarf2_gen_line_info saves seg/subseg info after it has already been
   clobbered by a subseg_new call.  This causes gas to accidentally emit code
   into the .debug_line section.

Wed Aug 25 20:20:33 1999  Jim Wilson  <wilson@cygnus.com>

	* dwarf2dbg.c (out_end_sequence): Correct comments.  Set last to
	ls.last_filename if last is less than zero.  Set ls.last_filename
	when allocating new entry.
	(dwarf2_gen_line_info): Save seg and subseg info before subseg_new
	call.

Index: dwarf2dbg.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gas/dwarf2dbg.c,v
retrieving revision 1.7
diff -p -r1.7 dwarf2dbg.c
*** dwarf2dbg.c	1999/07/23 22:12:34	1.7
--- dwarf2dbg.c	1999/08/26 03:34:48
*************** out_end_sequence ()
*** 359,365 ****
  /* Look up a filenumber either by filename or by filenumber.  If both
     a filenumber and a filename are specified, lookup by filename takes
     precedence.  If the filename cannot be found, it is added to the
!    filetable the filenumber for the new entry is returned.  */
  static int
  get_filenum (filenum, file)
       int filenum;
--- 359,365 ----
  /* Look up a filenumber either by filename or by filenumber.  If both
     a filenumber and a filename are specified, lookup by filename takes
     precedence.  If the filename cannot be found, it is added to the
!    filetable and the filenumber for the new entry is returned.  */
  static int
  get_filenum (filenum, file)
       int filenum;
*************** get_filenum (filenum, file)
*** 368,377 ****
    int i, last = filenum - 1;
    char char0 = file[0];
  
!   if (last >= ls.num_filenames)
      last = ls.last_filename;
  
!   /* do a quick check against the previously used filename: */
    if (ls.num_filenames > 0 && ls.file[last].name[0] == char0
        && strcmp (ls.file[last].name + 1, file + 1) == 0)
      return last + 1;
--- 368,379 ----
    int i, last = filenum - 1;
    char char0 = file[0];
  
!   /* If filenum is out of range of the filename table, then try using the
!      table entry returned from the previous call.  */
!   if (last >= ls.num_filenames || last < 0)
      last = ls.last_filename;
  
!   /* Do a quick check against the specified or previously used filenum.  */
    if (ls.num_filenames > 0 && ls.file[last].name[0] == char0
        && strcmp (ls.file[last].name + 1, file + 1) == 0)
      return last + 1;
*************** get_filenum (filenum, file)
*** 395,400 ****
--- 397,403 ----
      }
    ls.file[ls.num_filenames].dir = 0;
    ls.file[ls.num_filenames].name = file;
+   ls.last_filename = ls.num_filenames;
    return ++ls.num_filenames;
  }
  
*************** dwarf2_gen_line_info (addr, l)
*** 425,430 ****
--- 428,438 ----
    else
      return;	/* no filename, no filnum => no play */
  
+   /* Must save these before the subseg_new call, as that call will change
+      them.  */
+   saved_seg = now_seg;
+   saved_subseg = now_subseg;
+ 
    if (!ls.line_seg)
      {
  #ifdef BFD_ASSEMBLER
*************** dwarf2_gen_line_info (addr, l)
*** 445,452 ****
  #endif
      }
  
-   saved_seg = now_seg;
-   saved_subseg = now_subseg;
    subseg_set (ls.line_seg, DL_BODY);
  
    if (ls.text_seg != saved_seg || ls.text_subseg != saved_subseg)
--- 453,458 ----