Re: [rfa?] Add frame_align(); Was: ARM stack alignment on hand called functions

[Richard Earnshaw <rearnsha at arm dot com>]

> Richard Earnshaw <rearnsha@arm.com> writes:
> 
> |> > +/* Ensure that the ARM's stack pointer has the correct alignment for a
> |> > +   new frame.  */
> |> > +static CORE_ADDR
> |> > +arm_frame_align (struct gdbarch *gdbarch, CORE_ADDR addr)
> |> > +{
> |> > +  return (addr & -16);
> |> > +}
> |> 
> |> Yuck, two's complement assumption.
> 
> No, -16 is implicitly cast to bfd_vma, which is unsigned, and this
> operation is completely defined independent of the representation of
> signed integers.

Hmm, strictly speaking you are correct.  I don't have to like it though, 
and it means that the code is heavily dependent on the non-obvious fact 
that addr is an unsigned type to get the correct behaviour (if bfd_vma 
were to be changed to a signed type then this code would quietly break).

So I'll change my comment to:

Yuck, implicit cast of negative number to unsigned.

R.