struct of struct as return value

Hello,

I have a problem with structure as a return value, structure of structure
to be correct.

Here is c snippet that demonstrate the interface

```c
#ifndef foo_h
#define foo_h

#if defined DLL_EXPORT
#define DECLDIR __declspec(dllexport)
#define C_CALL  __cdecl

#else
#define DECLDIR __declspec(dllimport)
#define C_CALL
#endif

#pragma pack(1)

typedef struct in{
  float a;
  float b;
} In;


typedef struct data{
  float c;
  float d;
} Data;

typedef struct out{
  Data front;
  Data rear;
} Out;

#pragma pack(0)

DECLDIR Out C_CALL calc(In in);

#endif
```

I compile it with mingw32-gcc:
$ i686-pc-mingw32-gcc-4.5.2 -c foo.c -D DLL_EXPORT -Wall
$ i686-pc-mingw32-gcc-4.5.2 -shared -o foo.dll foo.o
-Wl,--out-implib,libfoo.a,--output-def,foo.def

That should be the python wrapper:
```python
from ctypes import Structure, c_float, CDLL

class In(Structure):
  _fields_ = [
    ('a', c_float),
    ('b', c_float),
  ]
  _pack_ = 1

class Data(Structure):
  _fields_ = [
    ('c', c_float),
    ('d', c_float),
  ]
  _pack_ = 1

class Out(Structure):
  _fields_ = [
    ('front', Data),
    ('rear',  Data),
  ]
  _pack_ = 1

lib = CDLL('foo.dll')

lib.calc.argtypes = In,
lib.calc.restype = Out

data = In(1.0, 2.0)

result = lib.calc(data)
```

The wrapper worked until, I used only a plain structure as a return value,
and it is working if I use pointer the get back the data, but unfortunatelly
I cannot change on the interface.

How should I handle this output?

thanks for your advice in advance,
gergo

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