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


On Jun 16 18:23, Corinna Vinschen wrote:
> 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.

I missed to add the fact that this can be demonstrated using an existing
testcase, gdb.base/ending-run.exp with mips64-elf.  There's a statement

  (gdb) cle *0xa0123456

Which fails with

  No breakpoint at 0xa0123456

The reason is that the breakpoint address is correctly stored sign
extended (0xffffffffa0123456), but the evaluation of "*0xa0123456"
evaluates the expression 0xa0123456 as unsigned int type.  This in
turn leads to the above described behaviour.

> 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.
> Ok to apply?
> Thanks,
> Corinna
> 	* mips-tdep.c (mips_integer_to_address): Call extract_signed_integer
> 	instead of unpack_long to maintain signedness.
> 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));


Corinna Vinschen
Cygwin Project Co-Leader
Red Hat

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