Re: PATCH: Fix DW_OP_deref for DW_TAG_formal_parameter

[Daniel Jacobowitz <drow at mvista dot com>]

Hi Elena, hi Jim,

Since this patch fixes HJ's problem, I'm submitting it for approval. 
It cuts out another user of decode_locdesc.  Why Fortran has arguments
passed by DW_OP_deref is something I don't really want to think
about... one of many things I don't like about Fortran :)

On Thu, Jul 31, 2003 at 12:22:07PM -0400, Daniel Jacobowitz wrote:
> On Thu, Jul 31, 2003 at 09:12:59AM -0700, H. J. Lu wrote:
> > On Thu, Jul 31, 2003 at 11:48:21AM -0400, Daniel Jacobowitz wrote:
> > > On Thu, Jul 31, 2003 at 08:44:05AM -0700, H. J. Lu wrote:
> > > > On Wed, Jul 30, 2003 at 08:27:53PM -0400, Daniel Jacobowitz wrote:
> > > > > On Wed, Jul 30, 2003 at 05:23:06PM -0700, H. J. Lu wrote:
> > > > > > On Wed, Jul 30, 2003 at 05:56:12PM -0400, Daniel Jacobowitz wrote:
> > > > > > > On Wed, Jul 30, 2003 at 02:54:21PM -0700, H. J. Lu wrote:
> > > > > > > > Does DW_OP_deref work correctly with gdb?
> > > > > > > 
> > > > > > > That depends on the context.  Things that use decode_locdesc, probably
> > > > > > > not.  As we find time, things are being converted to the full
> > > > > > > expression evaluator.  Location descriptions and frame bases should
> > > > > > > work.
> > > > > > 
> > > > > > I don't think it does. Intel Fortran compiler generartes DW_OP_deref.
> > > > > > I got
> > > > > 
> > > > > Location descriptions for parameters may not work fully.  Feel free to
> > > > > fix it, or to investigate the reasons why more thoroughly - search for
> > > > > LOC_COMPUTED_ARG, but I don't even think we generate those yet.
> > > > > 
> > > > 
> > 
> > > Please look more closely at what I suggested, and at how DW_OP_deref
> > > works for DW_TAG_variable (as opposed to DW_TAG_formal_parameter).  All
> > > of the above should be turned into LOC_COMPUTED_ARG.
> > > 
> > 
> > Thanks. This patch works for me.
> 
> Could you test this alternative?  The goal is to eliminate calls to
> decode_locdesc.


> 2003-07-31  Daniel Jacobowitz  <drow@mvista.com>
> 
> 	* dwarf2read.c (new_symbol): Use var_decode_location for parameters.
> 
> Index: dwarf2read.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2read.c,v
> retrieving revision 1.98
> diff -u -p -r1.98 dwarf2read.c
> --- dwarf2read.c	22 Jul 2003 15:41:59 -0000	1.98
> +++ dwarf2read.c	31 Jul 2003 16:21:04 -0000
> @@ -5207,32 +5207,10 @@ new_symbol (struct die_info *die, struct
>  	  attr = dwarf_attr (die, DW_AT_location);
>  	  if (attr)
>  	    {
> -	      SYMBOL_VALUE (sym) =
> -		decode_locdesc (DW_BLOCK (attr), objfile, cu_header);
> -	      if (isreg)
> -		{
> -		  SYMBOL_CLASS (sym) = LOC_REGPARM;
> -		  SYMBOL_VALUE (sym) = 
> -		    DWARF2_REG_TO_REGNUM (SYMBOL_VALUE (sym));
> -		}
> -	      else if (offreg)
> -		{
> -		  if (isderef)
> -		    {
> -		      if (basereg != frame_base_reg)
> -			dwarf2_complex_location_expr_complaint ();
> -		      SYMBOL_CLASS (sym) = LOC_REF_ARG;
> -		    }
> -		  else
> -		    {
> -		      SYMBOL_CLASS (sym) = LOC_BASEREG_ARG;
> -		      SYMBOL_BASEREG (sym) = DWARF2_REG_TO_REGNUM (basereg);
> -		    }
> -		}
> -	      else
> -		{
> -		  SYMBOL_CLASS (sym) = LOC_ARG;
> -		}
> +	      var_decode_location (attr, sym, objfile, cu_header);
> +	      /* FIXME drow/2003-07-31: Is LOC_COMPUTED_ARG necessary?  */
> +	      if (SYMBOL_CLASS (sym) == LOC_COMPUTED)
> +		SYMBOL_CLASS (sym) = LOC_COMPUTED_ARG;
>  	    }
>  	  attr = dwarf_attr (die, DW_AT_const_value);
>  	  if (attr)
> 

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer