This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: FYI: fix big-endian bug with DWARF_VALUE_STACK
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: tromey at redhat dot com
- Cc: gdb-patches at sourceware dot org
- Date: Tue, 23 Feb 2010 20:53:46 +0100 (CET)
- Subject: Re: FYI: fix big-endian bug with DWARF_VALUE_STACK
Tom Tromey wrote:
> 2010-02-23 Tom Tromey <tromey@redhat.com>
>
> * dwarf2loc.c (read_pieced_value) <DWARF_VALUE_STACK>: Correctly
> handle big-endian values.
> (dwarf2_evaluate_loc_desc) <DWARF_VALUE_STACK>: Likewise.
I'd recently been wondering about this piece of code (and in particular
its use of gdbarch_addr_bit) as well ...
> @@ -298,16 +298,14 @@ read_pieced_value (struct value *v)
>
> case DWARF_VALUE_STACK:
> {
> - gdb_byte bytes[sizeof (ULONGEST)];
> size_t n;
> int addr_size = gdbarch_addr_bit (c->arch) / 8;
> - store_unsigned_integer (bytes, addr_size,
> - gdbarch_byte_order (c->arch),
> - p->v.expr.value);
> n = p->size;
> if (n > addr_size)
> n = addr_size;
> - memcpy (contents + offset, bytes, n);
> + store_unsigned_integer (contents + offset, n,
> + gdbarch_byte_order (c->arch),
> + p->v.expr.value);
> }
> break;
The original code looks broken to me too. But even the new code
doesn't seem quite right: if the requested piece size p->size
is larger than addr_size, the remaining bytes of the output value
are left undefined (well, probably zeroed -- but that still doesn't
look correct on a big-endian machine ...).
Why would that code look at gdbarch_addr_bit at all? I think this
should simply do something like:
store_unsigned_integer (contents + offset, p->size,
gdbarch_byte_order (c->arch),
p->v.expr.value);
> @@ -476,19 +474,17 @@ dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame,
>
> case DWARF_VALUE_STACK:
> {
> - gdb_byte bytes[sizeof (ULONGEST)];
> ULONGEST value = (ULONGEST) dwarf_expr_fetch (ctx, 0);
> bfd_byte *contents;
> size_t n = ctx->addr_size;
>
> - store_unsigned_integer (bytes, ctx->addr_size,
> - gdbarch_byte_order (ctx->gdbarch),
> - value);
> retval = allocate_value (SYMBOL_TYPE (var));
> contents = value_contents_raw (retval);
> if (n > TYPE_LENGTH (SYMBOL_TYPE (var)))
> n = TYPE_LENGTH (SYMBOL_TYPE (var));
> - memcpy (contents, bytes, n);
> + store_unsigned_integer (contents, n,
> + gdbarch_byte_order (ctx->gdbarch),
> + value);
> }
> break;
Similiary here; why does this not simply use value_from_longest?
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com