orbit-python-list

[Orbit-python-list] (in Object obj) marshalling error

[Christian R. R. <ki...@as...>]

Using orbit-python (no idea if we're getting a Orbit error, however) and a
simple 

interface NamingObject {
        void bind(in Object obj);
};

interface, I have the following issues:

1) Calling bind with a simple object reference:

[...]
class Foo:
	pass
a=Foo()
nc.bind(a)

TypeError: Failed to marshal: Object Reference ()

even though a _is_ an object reference.

2) Didn't work? Ok, let's try a stringified IOR:

nc.bind(orb.object_to_string(a))

CORBA.SystemException: IDL:CORBA/MARSHAL:1.0: IDL:CORBA/MARSHAL:1.0

Hmm. I wonder why I get a different message?

3) Let's do something dumb now:

nc.bind(1)

TypeError: Failed to marshal: Object Reference ()

Ok, same error as my first non-ior attempt. Passing any other object gets
me the same error (strings, etc).

4) And what about

nc.bind(orb.object_to_string(1))

Segmentation fault

Hmm, boom. Orbit-python or plain Orbit?

The practical effect of this is that it's impossible to use orbit-python
with the Orbit nameserver as of now. We simply can't bind the servers to
names because bind() takes an object parameter. I've cut out the offending
code and will start looking for the issue; in the meantime, if Jason has
any ideas.. :-)

Take care,
--
/\/\ Christian Reis, Senior Engineer, Async Open Source, Brazil
~\/~ http://async.com.br/~kiko/ | [+55 16] 274 4311

Re: [Orbit-python-list] (in Object obj) marshalling error

[Roland M. <ma...@ec...>]

Christian Robottom Reis (2001-01-22 22:24:31 -0200) :

> Using orbit-python (no idea if we're getting a Orbit error, however) and a
> simple 
> 
> interface NamingObject {
>         void bind(in Object obj);
> };
> 
> interface, I have the following issues:
> 
> 1) Calling bind with a simple object reference:
> 
> [...]
> class Foo:
> 	pass
> a=Foo()
> nc.bind(a)
> 
> TypeError: Failed to marshal: Object Reference ()
> 
> even though a _is_ an object reference.

  Hm.  Is is a Python object reference, I'm not sure it's a CORBA
object reference.

> 2) Didn't work? Ok, let's try a stringified IOR:
> 
> nc.bind(orb.object_to_string(a))
> 
> CORBA.SystemException: IDL:CORBA/MARSHAL:1.0: IDL:CORBA/MARSHAL:1.0
> 
> Hmm. I wonder why I get a different message?

  For the same reason.  a is not of a type known by ORBit.

> 3) Let's do something dumb now:
> 
> nc.bind(1)
> 
> TypeError: Failed to marshal: Object Reference ()

  Same again.

  You can only marshal objects that are defined in a CORBA interface.

You should add an interface like:

interface Foo {
  attribute string bar ;
} ;

  Then you need to make your Python Foo class a subclass of
Your_module__POA.Foo: 

class Foo (Your_module__POA.Foo):
  def __init__ (self):
    self.bar = "Initial string"

  Only then will ORBit-Python know how to marshal your Foo objects.

> 4) And what about
> 
> nc.bind(orb.object_to_string(1))
> 
> Segmentation fault
> 
> Hmm, boom. Orbit-python or plain Orbit?

  That's a tricky question, and a nasty bug anyway.  I'll try to have
a look sometime.

> The practical effect of this is that it's impossible to use
> orbit-python with the Orbit nameserver as of now.

  I'm not so sure.  It's not like I have done it, but I would be more
convinced if you could retry with CORBA objects.

> We simply can't bind the servers to names because bind() takes an
> object parameter.

  Yep.  A CORBA object, not a Python object.

Roland.
-- 
Roland Mas

Et c'est tellement plus mignon de se faire traiter de con en chanson...
  -- in En chantant (Michel Sardou)

Re: [Orbit-python-list] (in Object obj) marshalling error

[Christian R. R. <ki...@as...>]

On 23 Jan 2001, Roland Mas wrote:

> > TypeError: Failed to marshal: Object Reference ()
> > 
> > even though a _is_ an object reference.
> 
>   Hm.  Is is a Python object reference, I'm not sure it's a CORBA
> object reference.

According to the CORBA Python Mappings,

 	If an operation expects parameters of the IDL Object type, any
	Python object representing an object reference might be passed as
	a value.

So I'm passing as a parameter a Python Object which I've just instantiated
from a class that inherits from a __POA class, so it _is_ a Corba Object.

> > Hmm. I wonder why I get a different message?
> 
>   For the same reason.  a is not of a type known by ORBit.

A different message, for the same reason? What I mean is that _any_ object
that I pass - be it local, Corba, or simple number/string objects get me
the same error. However, passing an IOR string gets me a different
one? Sounds strange, but I haven't looked at the source yet.

> You should add an interface like:
> 
> interface Foo {
>   attribute string bar ;
> } ;

Oh, I do have an interface for my Corba Object which I'm passing as a
parameter. The purpose of this exercise is binding an object - a factory
in this case - to the namingservice. The bind() call takes an Object as a
parameter, so I instantiate a factory and pass it on. However, the
marshalling breaks, and it breaks with any object I push through as well.

> > The practical effect of this is that it's impossible to use
> > orbit-python with the Orbit nameserver as of now.
> 
>   I'm not so sure.  It's not like I have done it, but I would be more
> convinced if you could retry with CORBA objects.

They were Corba Objects. I was incomplete in my explanation, and I'm
sorry, but the objects I was passing initially are Corba Objects with
interfaces defined in the IDL. And they get ht the exact same error as
plain Python objects, so it's strange.

Thanks a lot for the reply.

Take care,
--
/\/\ Christian Reis, Senior Engineer, Async Open Source, Brazil
~\/~ http://async.com.br/~kiko/ | [+55 16] 274 4311

Re: [Orbit-python-list] (in Object obj) marshalling error

[Jason T. <ta...@li...>]

> So I'm passing as a parameter a Python Object which I've just instantiated
> from a class that inherits from a __POA class, so it _is_ a Corba Object.

As Roland pointed out, Foo is a Python object, not derived from the
__POA class.  ORBit-Python has no idea what to do with that object, even
if it weren't broken. ;)

Basically ORBit-Python doesn't seem to handle generic object references
very well (at all) right now.  I made a change to my local copy that
_seems_ to correct the problem, but the change was so trivial that it
can't possibly be right, so I'll want to test it a little further before
I commit it.

> According to the CORBA Python Mappings,
> 
>  	If an operation expects parameters of the IDL Object type, any
> 	Python object representing an object reference might be passed as
> 	a value.

I think you might have misunderstood what this says, or maybe it's a
little ambiguous.  A Python object representing an object reference
looks like:

   class Foo(CosNaming__POA.NamingContext):
      pass
   a = Foo()
   a._this() # implicit activation
   ref = poa.servant_to_reference(a) 
   # ref is a python object that represents the object reference
   print ref

Yields:

   <CosNaming.NamingContext object at 80e2518>

I don't think the mapping specification says that in your example
bind(1) should work.  1 is not a CORBA object.  I think, though, it
might be a nice feature if ORBit-Python coerced servants into object
references in this situation.

> A different message, for the same reason? What I mean is that _any_ object
> that I pass - be it local, Corba, or simple number/string objects get me

No, a different message for a different reason.  I'll go through your
examples from your original email and explain what happened:

> 1) Calling bind with a simple object reference:

> [...]
> class Foo:
>    pass
> a=Foo()
> nc.bind(a)
> TypeError: Failed to marshal: Object Reference ()

Like I said earlier, ORBit-Python doesn't handle generic object
references.  However, even if it did, this wouldn't work because Foo
doesn't inherit a POA class.

> 2) Didn't work? Ok, let's try a stringified IOR:
> nc.bind(orb.object_to_string(a))
> CORBA.SystemException: IDL:CORBA/MARSHAL:1.0: IDL:CORBA/MARSHAL:1.0

I'm not entirely sure what happened here, but my guess is 'a' wasn't a
valid IOR (such as, for example, if it has trailing newlines and you're
not using the latest CVS version).

This exception was probably raised from object_to_string, not within
the bind stub.

> 3) Let's do something dumb now:
> nc.bind(1)
> TypeError: Failed to marshal: Object Reference ()

Well again, ORBit-Python won't handle the objref properly, but in this
case you're not passing it a CORBA object.  It sounds to me like you're
mixing up the Any type with the Object type. 

> 4) And what about
> nc.bind(orb.object_to_string(1))
> Segmentation fault

Okay, well this is a bug in ORBit-Python, to be sure.  ORBit-Python's
object_to_string doesn't do any sanity checking.  ORBit-Python happily
passes this over to ORBit, which in turn happily tries to dereference
this value (thinking it is a CORBA_Object) and kaboom.

This is documented actually in the source code, in CORBA_ORB.c:

   if (PyArg_ParseTuple(args, "O", &obj)) {
      // validate obj == CORBA_PyObject
      s = CORBA_ORB_object_to_string(self->obj, obj->obj, &self->ev);
 [ ... ]

It's just missing a FIXME :)

So, here the segfault happens inside object_to_string, not bind().

Anyway thanks for identifying this bug.  I'll hopefully commit some sort
of fix by the end of the day. :)

Jason.

Re: [Orbit-python-list] (in Object obj) marshalling error

[Christian R. R. <ki...@as...>]

On Tue, 23 Jan 2001, Jason Tackaberry wrote:

> > [...]
> > class Foo:
> >    pass
> > a=Foo()
> > nc.bind(a)
> > TypeError: Failed to marshal: Object Reference ()
> 
> Like I said earlier, ORBit-Python doesn't handle generic object
> references.  However, even if it did, this wouldn't work because Foo
> doesn't inherit a POA class.

You're right. My example was stupid. The problem I have is that ATM you
can't even pass a Corba Object as a parameter -- you get the exact same
error. As a simple example:

module Bar {
	interface Foo {
		void bind (in Object a);
	};
};

and the following servant:

#!/usr/bin/env python
import CORBA
import Bar,Bar__POA

class Foo(Bar__POA.Foo):
	def bind(self,i):
		print i

o=CORBA.ORB_init([],CORBA.ORB_ID)
p=o.resolve_initial_references("RootPOA")
f=Foo()
f._this()
ref = p.servant_to_reference(f)
print o.object_to_string(ref)
p._get_the_POAManager().activate()
o.run()

produce the same TypeError: Failed to marshal: Object Reference ()

when a client like this tries to call bind:

#!/usr/bin/env python
import sys,CORBA, Bar, Bar__POA

o=CORBA.ORB_init([],CORBA.ORB_ID)
f=o.string_to_object(sys.argv[1])

f.bind(f)

Okay, so I used f as a parameter to itself: it should work, no? And f _is_
a reference to a Corba object.

> I'm not entirely sure what happened here, but my guess is 'a' wasn't a
> valid IOR (such as, for example, if it has trailing newlines and you're
> not using the latest CVS version).

Actually, it was a valid IOR and ior-decode indicated it as such. I'm
using CVS orbit-python (and I check to see if it's been updated daily too
*grin*) But I can't seem to reproduct this right now.

> Well again, ORBit-Python won't handle the objref properly, but in this
> case you're not passing it a CORBA object.  It sounds to me like you're
> mixing up the Any type with the Object type. 

No, just trying (brokenly) to illustrate that I get the same error message
whether it's a Corba Object or a plain Python object. My example

class Foo:
	pass

should really have been

class Foo(Bar__POA.Foo)
	pass

but it still doesn't work, regardless :-)

> It's just missing a FIXME :)
> So, here the segfault happens inside object_to_string, not bind().

Ok, this is reasonable, I was just wondering. :-)

Take care,
--
/\/\ Christian Reis, Senior Engineer, Async Open Source, Brazil
~\/~ http://async.com.br/~kiko/ | [+55 16] 274 4311

Re: [Orbit-python-list] (in Object obj) marshalling error

[Jason T. <ta...@li...>]

> You're right. My example was stupid. The problem I have is that ATM you
> can't even pass a Corba Object as a parameter -- you get the exact same
> error. As a simple example:

Right.  It's a bug. :)   I've little free time until tomorrow night, so
I may not commit a fix until then.

But give this a try: in marshal.c, line 473 (or there abouts, I'm a
little out of sync), change:

   if (glue)

to

   if (glue || !strcmp(tc->repo_id, ""))

Like I said, this is so trivial it can't possibly work, right? :)  Let
me know.

Cheers,
Jason.

Re: [Orbit-python-list] (in Object obj) marshalling error

[Christian R. R. <ki...@as...>]

On Tue, 23 Jan 2001, Jason Tackaberry wrote:

>    if (glue || !strcmp(tc->repo_id, ""))

What exactly are repo_id and repo_object? Can't seem to follow this bit of
the code.

Take care,
--
/\/\ Christian Reis, Senior Engineer, Async Open Source, Brazil
~\/~ http://async.com.br/~kiko/ | [+55 16] 274 4311

Re: [Orbit-python-list] (in Object obj) marshalling error

[Jason T. <ta...@li...>]

> >    if (glue || !strcmp(tc->repo_id, ""))
> 
> What exactly are repo_id and repo_object? Can't seem to follow this bit of
> the code.

repo_id is the repository id of the interface (or struct, or union, or
enum, etc.) of the type.  For example, IDL:Module/Interface:1.0.

The snippet of code above checks to see if we know about the interface
described by the repo_id (it looks it up in the hash table), or if the
repo_id is an empty string, which means that the type is an generic
object reference.  I'm really not sure why ORBit uses an empty repo id
and not IDL:CORBA/Object.

Jason.

[Orbit-python-list] ORBit Object repository ID

[Christian R. R. <ki...@as...>]

On Fri, 26 Jan 2001, Jason Tackaberry wrote:

> > >    if (glue || !strcmp(tc->repo_id, ""))
> > 
> > What exactly are repo_id and repo_object? Can't seem to follow this bit of
> > the code.
> 
> repo_id is the repository id of the interface (or struct, or union, or
> enum, etc.) of the type.  For example, IDL:Module/Interface:1.0.
> 
> The snippet of code above checks to see if we know about the interface
> described by the repo_id (it looks it up in the hash table), or if the
> repo_id is an empty string, which means that the type is an generic
> object reference.  I'm really not sure why ORBit uses an empty repo id
> and not IDL:CORBA/Object.

Eliott, anyone..? cares to comment as to why we're using "" for repository
id for CORBA/Object types? Or is something getting lost along the way?

Take care,
--
/\/\ Christian Reis, Senior Engineer, Async Open Source, Brazil
~\/~ http://async.com.br/~kiko/ | [+55 16] 274 4311

Re: [Orbit-python-list] (in Object obj) marshalling error

[Christian R. R. <ki...@as...>]

On Tue, 23 Jan 2001, Jason Tackaberry wrote:

>    if (glue || !strcmp(tc->repo_id, ""))

Fix worked - at least the object reference gets passed on. I recompiled
without ORBIT_PYTHON_NOT_THREADED and of course, when I called a method
that was part of an object I was passing as a parameter, I got the dreaded

Fatal Python error: PyThreadState_Get: no current thread

error. Recompiling with -DORBIT_PYTHON_NOT_THREADED worked fine. Thanks.


Take care,
--
/\/\ Christian Reis, Senior Engineer, Async Open Source, Brazil
~\/~ http://async.com.br/~kiko/ | [+55 16] 274 4311