[Libguestfs] [PATCH libnbd 5/6] generator: Implement OClosure.

[Richard W.M. Jones]

On Tue, Aug 13, 2019 at 06:34:11AM -0500, Eric Blake wrote:
> On 8/13/19 5:06 AM, Richard W.M. Jones wrote:
> > An optional Closure parameter, but otherwise works the same way as
> > Closure.
> 
> > @@ -3778,6 +3777,7 @@ let generate_lib_api_c () =
> >      ) args;
> >      List.iter (
> >        function
> > +      | OClosure { cbname } -> pr ", %s_callback ? \"<fun>\" : \"NULL\"" cbname
> 
> Well, it also permits a NULL fn pointer.

This is right isn't it?

> > @@ -4383,6 +4387,16 @@ let print_python_binding name { args; optargs; ret; may_set_error } =
> >    ) args;
> >    List.iter (
> >      function
> > +    | OClosure { cbname } ->
> > +       pr "  if (%s_user_data) {\n" cbname;
> > +       pr "    /* Increment refcount since pointer may be saved by libnbd. */\n";
> > +       pr "    Py_INCREF (%s_user_data);\n" cbname;
> > +       pr "    if (!PyCallable_Check (%s_user_data)) {\n" cbname;
> 
> I don't think PyNone is callable; this probably needs to gain a special
> case for when the user omitted the optional argument and we thus...

Yeah I'm not sure about this, plus we don't have any test coverage of
it.  But it doesn't work ...

$ nbdkit null --run './run nbdsh --connect nbd://localhost -c "buf = nbd.Buffer(512)" -c "h.aio_pread_callback (buf, 0)"'
Traceback (most recent call last):
  File "/usr/lib64/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib64/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/rjones/d/libnbd/python/nbd.py", line 1417, in <module>
    nbdsh.shell()
  File "/home/rjones/d/libnbd/python/nbdsh.py", line 62, in shell
    exec (c)
  File "<string>", line 1, in <module>
  File "/home/rjones/d/libnbd/python/nbd.py", line 923, in aio_pread_callback
    return libnbdmod.aio_pread_callback (self._o, buf._o, offset, completion, flags)
TypeError: callback parameter completion is not callable

It seems like the "if (%_user_data) {" test at the top is not
sufficient to tell me if the value is None and I've got to do
something else instead.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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