Gdb generates location list without DW_AT_frame_base

["H. J. Lu" <hjl@lucon.org>]

On Thu, Dec 30, 2004 at 03:07:20PM -0500, Daniel Jacobowitz wrote:
> On Thu, Dec 30, 2004 at 11:56:42AM -0800, H. J. Lu wrote:
> > DW_AT_frame_base may be needed for location lists of local variables.
> > But in case of tls_symbolic_operand, there is no local variable.
> > Location lists are used for function parameters.
> 
> Then why is GDB calling get_frame_base?  It is only called for
> DW_OP_fbreg.  If we don't have a frame base, we don't know what
> DW_OP_fbreg refers to.

Gcc generates:

 <1><28c955>: Abbrev Number: 47 (DW_TAG_subprogram)
     DW_AT_sibling     : <28c98f>
     DW_AT_external    : 1
     DW_AT_name        : (indirect string, offset: 0x3875d):
tls_symbolic_operand
     DW_AT_decl_file   : 1
     DW_AT_decl_line   : 471
     DW_AT_prototyped  : 1
     DW_AT_type        : <2887cb>
     DW_AT_low_pc      : 0x826c1d0
     DW_AT_high_pc     : 0x826c1fc
 <2><28c96f>: Abbrev Number: 48 (DW_TAG_formal_parameter)
     DW_AT_name        : op
     DW_AT_decl_file   : 1
     DW_AT_decl_line   : 470
     DW_AT_type        : <288a7b>
     DW_AT_location    : 120fbf (location list)
 <2><28c97e>: Abbrev Number: 49 (DW_TAG_formal_parameter)
     DW_AT_name        : (indirect string, offset: 0x3db66): mode
     DW_AT_decl_file   : 1
     DW_AT_decl_line   : 470
     DW_AT_type        : <288e5d>
     DW_AT_location    : 121018 (location list)

for

int
tls_symbolic_operand (rtx op, enum machine_mode mode ATTRIBUTE_UNUSED)
{
  return ((GET_CODE (op) == SYMBOL_REF) && (SYMBOL_REF_TLS_MODEL (op)
!= 0)) && (mode == VOIDmode || GET_MODE (op) == mode);
}

It may be a gcc bug after all.

> 
> GDB should issue an error instead of crashing, but that's as far as we
> can go.

This patch does something like that

--- dwarf2loc.c 2004-12-30 12:01:34.140350763 -0800
+++ dwarf2loc.c.new     2004-12-30 11:54:24.759408333 -0800
@@ -164,13 +164,16 @@ dwarf_expr_frame_base (void *baton, unsi
       *start = find_location_expression (symbaton, length,
                                         get_frame_pc
(debaton->frame));
     }
-  else
+  else if (SYMBOL_OPS (framefunc) == &dwarf2_locexpr_funcs)
     {
       struct dwarf2_locexpr_baton *symbaton;
       symbaton = SYMBOL_LOCATION_BATON (framefunc);
       *length = symbaton->size;
       *start = symbaton->data;
     }
+  else
+    error ("Invalid frame base function for \"%s\".",
+          SYMBOL_NATURAL_NAME (framefunc));

   if (*start == NULL)
     error ("Could not find the frame base for \"%s\".",


H.J.