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

[Jim Blandy <jimb@redhat.com>]

"Philippe De Muyter" <phdm@macqel.be> writes:
> Should the following lines not be kept outside of the conditional block ?
> 
>        info->min_lineno_offset = 0;
>        info->max_lineno_offset = 0;

Sure, those can be moved outside.  

I was just thinking of those as just establishing the pre-condition
for the loop that bfd_map_over_sections does.  Those fields are never
used outside the "read the line number table" block, and the worker
function for bfd_map_over_sections --- effectively, the loop body.  In
that light, it makes more sense to keep them right next to the call,
as they are in the original code.

Here's a revised patch, if you prefer the initializations outside.

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/src/src/gdb/coffread.c,v
retrieving revision 1.26
diff -c -r1.26 coffread.c
*** gdb/coffread.c	19 Mar 2002 19:00:03 -0000	1.26
--- gdb/coffread.c	26 Jun 2002 18:19:07 -0000
***************
*** 593,608 ****
  
  /* 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, (void *) 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.  */
  
--- 593,626 ----
  
  /* End of warning */
  
    info->min_lineno_offset = 0;
    info->max_lineno_offset = 0;
  
!   /* 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.  */
!       bfd_map_over_sections (abfd, find_linenos, (void *) 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.  */