ffi: support programmable abort return value.

* ffi.c (stuct txr_ffi_closure): New member, abort_retval.
(ffi_closure_mark_op): Mark the new member.
(ffi_closure_dispatch_safe): Implement the abort_retval.
If it is not nil, use put to place the value into the
return buffer.  There is a risk that this could also throw
an exception, which is no longer protected: programer's
problem.
(ffi_make_closure): New abort_ret_in argument, which is
defaulted and stored.
(ffi_init): Update registration of ffi-make-closure to
reflect new argument.

* ffi.h (ffi_make_closure): Declaration updated.

* share/txr/stdlib/ffi.tl (sys:deffi-cb-expander):
Add abort-retval parameter; insert into ffi-make-closure
call.
(deffi-cb): Take optional abort-retval expression;
pass it down to the expander function.
(deffi-cb-unsafe): Pass nil as abort-retval down to expander.

* txr.1: Documented.

1 files changed, 1 insertions, 1 deletions

diff --git a/ffi.h b/ffi.h
index 8eb54a78..4364a615 100644
--- a/ffi.h
+++ b/ffi.h
@@ -53,7 +53,7 @@ extern val ffi_type_s, ffi_call_desc_s, ffi_closure_s;
 
 val ffi_type_compile(val syntax);
 val ffi_make_call_desc(val ntotal, val nfixed, val rettype, val argtypes);
-val ffi_make_closure(val fun, val call_desc, val safe_p_in);
+val ffi_make_closure(val fun, val call_desc, val safe_p_in, val abort_ret_in);
 mem_t *ffi_closure_get_fptr(val closure);
 val ffi_call_wrap(val ffi_call_desc, val fptr, val args);
 val ffi_typedef(val name, val type);