Re: [PATCH 2/5] powerpc64-aix processing xlC generated line table

["Ulrich Weigand" <uweigand at de dot ibm dot com>]

Raunaq 12 wrote:

> xlc generated binaries have a line table which is not the same as GCC.
> GCC compiled binaries have an extra line entry in the line table to
> signify start of a function whereas xlc does not have this entry.
> 
> Due to this difference, commands like break <function name> and
> list <function name> give wrong results.
> 
> To fix this issue I have written a function modify_xlc_linenos
> which will add a line table entry at the function start points
> if there is no extra entry in the line table as in the case of xlc.
> 
> Hence,
> breakpoints and listing functions will work as expected even for xlc
> compiled binaries.

I don't have much experience with the XCOFF file format or the
XLC debug info ...

Did you confirm  -via test suite runs-  that:
- this patch improves results when using XLC, and
- this patch does not regress when using GCC?

> +/* xlc compiled binaries have one less entry in the line table.
> +   So the function entry lines marked as line number equal to 0
> +   will be retained in the line table with line numbers equal
> +   to its succeeding line table entry.	*/
> +
> +static struct linetable *
> +modify_xlc_linenos (struct linetable *lineTb)
> +{
> + int jj;
> + for (jj = 0; jj < lineTb->nitems; jj++)
> +  {
> +   if (lineTb->item[jj].line == 0 && (lineTb->item[jj].pc
> +                                    != lineTb->item[jj + 1].pc))
> +        lineTb->item[jj].line = lineTb->item[jj + 1].line;
> +  }
> + return lineTb;
> +}
> +
>  /* Global variable to pass the psymtab down to all the routines involved
>     in psymtab to symtab processing.  */
>  static struct partial_symtab *this_symtab_psymtab;
> @@ -698,10 +718,14 @@
> 
>        lv = main_subfile.line_vector;
> 
> +      /* Add extra line entry in case of xlc compiled binaries.	*/
> +
> +      lineTb = modify_xlc_linenos (lv);
> +
>        /* Line numbers are not necessarily ordered.  xlc compilation will
>           put static function to the end.  */
> 
> -      lineTb = arrange_linetable (lv);
> +      lineTb = arrange_linetable (lineTb);
>        if (lv == lineTb)
>  	{
>  	  current_subfile->line_vector = (struct linetable *)
> @@ -730,10 +754,14 @@
> 
>  	  lv = (inclTable[ii].subfile)->line_vector;
> 
> +          /* Add extra line entry in case of xlc compiled binaries */
> +
> +          lineTb = modify_xlc_linenos (lv);
> +
>  	  /* Line numbers are not necessarily ordered.  xlc compilation will
>  	     put static function to the end.  */
> 
> -	  lineTb = arrange_linetable (lv);
> +	  lineTb = arrange_linetable (lineTb);

Is there any reason why the change done in the new modify_xlc_linenos
routine cannot be done inline in arrange_linetable?   The latter
routine already appears to do a number of checks related to the
end of line table entries ...

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com