Possible bug with Transfer annotation?

[Phil Thompson]

On 12/12/2022 00:35, Arthur Gordon-Wright wrote:
> Hi,
> 
> The reproducing code for this issue involves several files, so I've 
> created
> a gist:
> 
> https://gist.github.com/ArthurGW/a3e906e2d1247adc140f988d06c883f3
> 
> It seems like between SIP 6.0.3 and SIP 6.1.0 (and up to the current
> version) the /Transfer/ annotation is no longer working for function 
> (i.e.
> not method) arguments. Previously if I had a structure something like 
> this:
> 
>     %Module(name=test_transfer)
> 
>     class Test {};
> 
>     void test_install(Test *obj /Transfer/);
> 
> with the wrapped C++ function `test_install` assigning the `Test` 
> object
> `obj` to a `std::unique_ptr` that is not cleared while the program is
> running, and I called this from python as:
> 
>     import test_transfer
>     test_transfer.test_install(test_transfer.Test())
> 
> then the associated C++ and Python `Test` objects were kept alive. 
> However,
> since SIP 6.1, the destructor on the `Test` object is called 
> immediately
> when `test_install` finishes, so the `std::unique_ptr` ends up pointing 
> to
> freed memory.
> 
> There are two fixes I can do for this myself: either make 
> `test_install` a
> method on a `Holder` object (see files named "METHOD..." in the gist), 
> or
> write the transfer code myself (WORKING.sip) as:
> 
>     void test_install(PyObject *obj /TypeHintIn = "Test"/);
>     %MethodCode
> 
>     Test *tobj{reinterpret_cast<Test*>(sipConvertToType(a0, 
> sipType_Test,
> NULL, SIP_NOT_NONE, 0, &sipIsErr))};
>     sipTransferTo(a0, Py_None);
> 
>     test_install(tobj);
>     %End
> 
> It feels like this second fix is how that annotation is supposed to 
> work,
> so I shouldn't need to do this?
> 
> (Setup: python 3.8.8, on windows.)
> 
> Cheers,
> Arthur

Should be fixed in the next snapshot. It's actually a bug in the ABI v13 
sip module.

Thanks,
Phil