Also: problem with return value in ffi_call on PPC64.

["Kaz Kylheku (libffi)" <382-725-6798@kylheku.com>]

Hi all,

It turns out that return values from foreign calls are also not working 
in the way I expect.

For instance, the int return value of dup comes out as zero if a file 
descriptor is returned.
The -1 value emerges properly due to sign extension:

1> (with-dyn-lib nil (deffi dup-fd "dup" int (int)))
#:lib-0175
2> (dup-fd 0)
0
3> (dup-fd 4)
-1
4> (dup-fd 3)
0
5> (dup-fd 4)
0
6> (dup-fd 5)
0
7> (dup-fd 7)
-1
8> (dup-fd 7)
-1

Are users supposed to assume that the return value has been widened to a 
register-wide (8 byte) value regardless of its declared FFI type?

Why doesn't that convention apply to the arguments, then? When dup is 
being called above, the int value is being written at the bottom of the 
argument buffer, not displaced by four bytes.