The segfault occurs both with CFUNCTYPE and PYFUNCTYPE in
ffi_prep_incoming_args_SYSV(). I'm not very familiar with
either suncc or the dbx debugger, and I can't get dbx to
step into that function (compiled with -g, libffi is not
stripped as far as I can see). Anyway, here's what I got:

(dbx) stop at ffi.c:403 
(2) stop at "ffi.c":403
(dbx) run
Running: python 
(process id 29932)
Python 3.3.0a0 (default:5c8b6e03ebfe+, Sep  7 2011, 15:48:46) [C] on sunos5
Type "help", "copyright", "credits" or "license" for more information.
>>> from ctypes import *
Reading _struct.so
Reading libscf.so.1
Reading libuutil.so.1
Reading libgen.so.1
Reading libmd.so.1
Reading libmp.so.2
>>> proto = CFUNCTYPE(None)
>>> def func():
        return (1, "abc", None)
...
>>> cb = proto(func)
>>> cb()
stopped in ffi_closure_SYSV_inner at line 403 in file "ffi.c"
  403     ffi_prep_incoming_args_SYSV(args, respp, arg_area, cif);
(dbx) step
signal SEGV (no mapping at the fault address) in ffi_closure_SYSV_inner at line 403 in file "ffi.c"
  403     ffi_prep_incoming_args_SYSV(args, respp, arg_area, cif);