Re: [PATCH] mips-tdep.c: Fix bug in evaluating signed address

Corinna Vinschen
2006-07-13T11:55:02Z

On Jul 12 15:31, Daniel Jacobowitz wrote:
> On Fri, Jun 16, 2006 at 06:23:32PM +0200, Corinna Vinschen wrote:
> > Hi,
> >
> > the below patch fixes the mips_integer_to_address function. What
> > happens is this:
> >
> > If the incoming type is an *unsigned* value, then unpack_long takes the
> > (un)signedness into account. This results in `val' not being signed
> > extended, as the mips_integer_to_address function was originally
> > designed for.
> >
> > So, to enforce correct signedness of the resulting address, I changed
> > the unpack_long call to extract_signed_integer. This way, val is always
> > sign extended and the mips address is correctly signed.
>
> I might be missing something, but isn't the function mostly redundant
> now?
>
> > Index: gdb/mips-tdep.c
> > ===================================================================
> > RCS file: /cvs/cvsfiles/gnupro/gdb/mips-tdep.c,v
> > retrieving revision 1.24
> > diff -u -p -r1.24 mips-tdep.c
> > --- gdb/mips-tdep.c 15 Jun 2006 08:57:17 -0000 1.24
> > +++ gdb/mips-tdep.c 16 Jun 2006 16:15:48 -0000
> > @@ -4749,7 +4749,7 @@ mips_integer_to_address (struct gdbarch
> > struct type *type, const gdb_byte *buf)
> > {
> > gdb_byte *tmp = alloca (TYPE_LENGTH (builtin_type_void_data_ptr));
> > - LONGEST val = unpack_long (type, buf);
> > + LONGEST val = extract_signed_integer (buf, TYPE_LENGTH (type));
> > store_signed_integer (tmp, TYPE_LENGTH (builtin_type_void_data_ptr), val);
> > return extract_signed_integer (tmp,
> > TYPE_LENGTH (builtin_type_void_data_ptr));
>
> Those last two have got to be a no-op.

Hmm, yes, you're right. I didn't realize that when changing unpack_long
to extract_signed_integer. Thanks, correct version below.

Corinna

* mips-tdep.c (mips_integer_to_address): Simplify be calling
extract_signed_integer directly. Fix comment.

Index: mips-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/mips-tdep.c,v
retrieving revision 1.396
diff -u -p -r1.396 mips-tdep.c
--- mips-tdep.c 19 Jun 2006 18:50:09 -0000 1.396
+++ mips-tdep.c 13 Jul 2006 11:36:13 -0000
@@ -4647,19 +4647,14 @@ mips_register_sim_regno (int regnum)
}

-/* Convert an integer into an address. By first converting the value
- into a pointer and then extracting it signed, the address is
- guarenteed to be correctly sign extended. */
+/* Convert an integer into an address. Extracting the value signed
+ guarantees a correctly sign extended address. */

static CORE_ADDR
mips_integer_to_address (struct gdbarch *gdbarch,
struct type *type, const gdb_byte *buf)
{
- gdb_byte *tmp = alloca (TYPE_LENGTH (builtin_type_void_data_ptr));
- LONGEST val = unpack_long (type, buf);
- store_signed_integer (tmp, TYPE_LENGTH (builtin_type_void_data_ptr), val);
- return extract_signed_integer (tmp,
- TYPE_LENGTH (builtin_type_void_data_ptr));
+ return (CORE_ADDR) extract_signed_integer (buf, TYPE_LENGTH (type));
}

static void