Re: N_SLINE fix for _bfd_stab_section_find_nearest_address() is broken

[Daniel Jacobowitz <drow at mvista dot com>]

On Tue, May 28, 2002 at 10:02:34AM +0100, Nick Clifton wrote:
> Hi Daniel,
> 
>   Your patch to work around a bug in 2.95.3 emitting N_SLINE data late
>   is causing the arm-coff port to failed the linker's undefined line
>   test when operating in Thumb mode.
> 
>     2002-03-20  Daniel Jacobowitz  <drow@mvista.com>
> 
> 	* syms.c (_bfd_stab_section_find_nearest_line): Use the first
> 	N_SLINE encountered if we see an N_FUN before any N_SLINE.
> 
>   I have tracked it down to this code in  _bfd_stab_section_find_nearest_address():
> 
> 	case N_SLINE:
> 	case N_DSLINE:
> 	case N_BSLINE:
> 	  /* A line number.  The value is relative to the start of the
>              current function.  */
> 	  val = indexentry->val + bfd_get_32 (abfd, stab + VALOFF);
> 	  /* If this line starts before our desired offset, or if it's
> 	     the first line we've been able to find, use it.  The
> 	     !saw_line check works around a bug in GCC 2.95.3, which emits
> 	     the first N_SLINE late.  */
> 	  if (!saw_line || val <= offset)
> 	    {
> 	      *pline = bfd_get_16 (abfd, stab + DESCOFF);
>      [snip]
>             }
> 	  if (val > offset)
> 	    done = true;
> 	  saw_line = true;
> 
>   The problem is that 'saw_line' is reset every time around the for
>   loop so *pline will be set to the last N_SLINE directive
>   encountered, even if it is *greater* than the target address.

Yes, your analysis makes sense to me; the way it's currently written
a great deal of the switch statement is actually dead code.  Please
check in your fix.

> 2002-05-28  Nick Clifton  <nickc@cambridge.redhat.com>
> 
> 	* syms.c (_bfd_stab_section_find_nearest_line): Move
> 	declaration and initialisation of saw_line and saw_func out of
> 	for loop.
> 
> Index: bfd/syms.c
> ===================================================================
> RCS file: /cvs/src/src/bfd/syms.c,v
> retrieving revision 1.21
> diff -c -3 -p -w -r1.21 syms.c
> *** bfd/syms.c	23 May 2002 13:12:47 -0000	1.21
> --- bfd/syms.c	28 May 2002 08:58:57 -0000
> *************** _bfd_stab_section_find_nearest_line (abf
> *** 883,888 ****
> --- 883,889 ----
>     char *file_name;
>     char *directory_name;
>     int saw_fun;
> +   boolean saw_line, saw_func;
>   
>     *pfound = false;
>     *pfilename = bfd_get_filename (abfd);
> *************** _bfd_stab_section_find_nearest_line (abf
> *** 1239,1251 ****
>     directory_name = indexentry->directory_name;
>     str = indexentry->str;
>   
>     for (; stab < (indexentry+1)->stab; stab += STABSIZE)
>       {
> !       boolean done, saw_line, saw_func;
>         bfd_vma val;
>   
> -       saw_line = false;
> -       saw_func = false;
>         done = false;
>   
>         switch (stab[TYPEOFF])
> --- 1240,1252 ----
>     directory_name = indexentry->directory_name;
>     str = indexentry->str;
>   
> +   saw_line = false;
> +   saw_func = false;
>     for (; stab < (indexentry+1)->stab; stab += STABSIZE)
>       {
> !       boolean done;
>         bfd_vma val;
>   
>         done = false;
>   
>         switch (stab[TYPEOFF])
> 

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer