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

[Jim Blandy <jimb at redhat dot com>]

Joel Brobecker has said in private E-mail that his earlier concerns
have been addressed, so I've committed this change.

Jim Blandy <jimb@redhat.com> writes:

> "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.  */
>