Gdb generates location list without DW_AT_frame_base
H. J. Lu
hjl@lucon.org
Thu Dec 30 20:23:00 GMT 2004
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.
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