Re: [Patch] libffi: Add MIPS64 support.

[David Daney <ddaney at avtrex dot com>]

Richard Sandiford wrote:
> David Daney <ddaney@avtrex.com> writes:
>   
> > +          /* The size of a pointer depends on the ABI */
> > +          if (type == FFI_TYPE_POINTER)
> > +            type =
> > +              (ecif->cif->abi == FFI_N64) ? FFI_TYPE_UINT64 : FFI_TYPE_UINT32;
> >     
>
> Was there a reason for preferring UINT to SINT here?  Naively, I'd have
> expected to see pointers treated as signed, especially for n32.  I can well
> imagine it makes no practical difference.  I just thought I'd ask.
>   

That sequence happens twice.

In the first case, you are probably correct. We are copying the pointer 
into a wider  type.   In practice it does not matter because all valid 
user space pointers have the high bit clear so there would never be a 
case where the not sign extending would produce a different result than 
if you did sign extend.

In the second case the bits are copied to a location of the same width 
as a pointer so sign extension is not an issue.

I will look at this again and perhaps change it before committing.

David Daney.