RFA: don't read coff line number unless we have symbols too

[Jim Blandy <jimb@redhat.com>]

2002-03-06  Jim Blandy  <jimb@redhat.com>

	* coffread.c (coff_symfile_read): Don't try to read the line
	number table from disk if the image file doesn't have a symbol
	table; we'll never actually look at the info anyway, and Windows
	ships DLL's with bogus file offsets for the line number data.

Index: gdb/coffread.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gdb/coffread.c,v
retrieving revision 1.182
diff -c -r1.182 coffread.c
*** gdb/coffread.c	2001/09/25 02:35:52	1.182
--- gdb/coffread.c	2002/03/06 23:12:00
***************
*** 622,637 ****
  
  /* End of warning */
  
!   /* Read the line number table, all at once.  */
!   info->min_lineno_offset = 0;
!   info->max_lineno_offset = 0;
!   bfd_map_over_sections (abfd, find_linenos, (PTR) info);
  
!   make_cleanup (free_linetab_cleanup, 0 /*ignore*/);
!   val = init_lineno (abfd, info->min_lineno_offset,
! 		     info->max_lineno_offset - info->min_lineno_offset);
!   if (val < 0)
!     error ("\"%s\": error reading line numbers\n", name);
  
    /* Now read the string table, all at once.  */
  
--- 622,654 ----
  
  /* End of warning */
  
!   /* Only read line number information if we have symbols.
  
!      On Windows NT, some of the system's DLL's have sections with
!      PointerToLinenumbers fields that are non-zero, but point at
!      random places within the image file.  (In the case I found,
!      KERNEL32.DLL's .text section has a line number info pointer that
!      points into the middle of the string `lib\\i386\kernel32.dll'.)
! 
!      However, these DLL's also have no symbols.  The line number
!      tables are meaningless without symbols.  And in fact, GDB never
!      uses the line number information unless there are symbols.  So we
!      can avoid spurious error messages (and maybe run a little
!      faster!) by not even reading the line number table unless we have
!      symbols.  */
!   if (num_symbols > 0)
!     {
!       /* Read the line number table, all at once.  */
!       info->min_lineno_offset = 0;
!       info->max_lineno_offset = 0;
!       bfd_map_over_sections (abfd, find_linenos, (PTR) info);
! 
!       make_cleanup (free_linetab_cleanup, 0 /*ignore*/);
!       val = init_lineno (abfd, info->min_lineno_offset,
!                          info->max_lineno_offset - info->min_lineno_offset);
!       if (val < 0)
!         error ("\"%s\": error reading line numbers\n", name);
!     }
  
    /* Now read the string table, all at once.  */