How do I convert from pyo3::ffi::PyFrameObject to pyo3::types::PyFrame?

[LilyFoote]

I'm pretty new to Rust, so I might be missing something.

I'm trying to create a Rust implementation of a Python profiler. So far I have got a very basic profiling callback implemented:

use pyo3::ffi;
use pyo3::prelude::*;

extern "C" fn profile(
    _obj: *mut ffi::PyObject,
    _frame: *mut ffi::PyFrameObject,
    what: i32,
    _arg: *mut ffi::PyObject,
) -> i32 {
    if what == ffi::PyTrace_CALL {
        println!("Call");
    } else if what == ffi::PyTrace_RETURN {
        println!("Return");
    }
    0
}

#[pyfunction]
fn register_profiler(profiler: PyObject) {
    unsafe {
        ffi::PyEval_SetProfile(Some(profile), profiler.into_ptr());
    }
}

/// A Python module implemented in Rust.
#[pymodule]
fn _kolo(_py: Python, m: &PyModule) -> PyResult<()> {
    m.add_function(wrap_pyfunction!(register_profiler, m)?)?;
    Ok(())
}

I now want to update my profile function to call the profiler object passed to register_profiler. This is passed by python to profile as the first argument _obj. To call this object, I'm converting the ffi::PyObject to a PyObject with from_owned_ptr_or_err and converting _arg to a PyObject too:

extern "C" fn profile(
    _obj: *mut ffi::PyObject,
    _frame: *mut ffi::PyFrameObject,
    what: i32,
    _arg: *mut ffi::PyObject,
) -> i32 {
    if what == ffi::PyTrace_CALL {
        println!("Call");
        Python::with_gil(|py| {
            let obj = PyObject::from_owned_ptr_or_err(py, _obj);
            let arg = PyObject::from_owned_ptr_or_err(py, _arg);
            let args = (_frame, "call", arg.expect(""));
            obj.expect("").call1(py, args);
        })
    } else if what == ffi::PyTrace_RETURN {
        println!("Return");
    }
    0
}

This fails with the following error:

error[E0277]: the trait bound `*mut PyFrameObject: IntoPy<Py<PyAny>>` is not satisfied                           
   --> src/lib.rs:16:38
    |
16  |             obj.expect("").call1(py, args);
    |                            -----     ^^^^ the trait `IntoPy<Py<PyAny>>` is not implemented for `*mut PyFrameObject`
    |                            |
    |                            required by a bound introduced by this call
    |
    = help: the following other types implement trait `IntoPy<T>`:
              <&'a OsString as IntoPy<Py<PyAny>>>
              <&'a Path as IntoPy<Py<PyAny>>>
              <&'a PathBuf as IntoPy<Py<PyAny>>>
              <&'a PyErr as IntoPy<Py<PyAny>>>
              <&'a String as IntoPy<Py<PyAny>>>
              <&'a [u8] as IntoPy<Py<PyAny>>>
              <&'a str as IntoPy<Py<PyAny>>>
              <&'a str as IntoPy<Py<PyString>>>
            and 158 others
    = note: required because of the requirements on the impl of `IntoPy<Py<PyTuple>>` for `(*mut PyFrameObject, &str, Py<PyAny>)`
note: required by a bound in `Py::<T>::call1`
   --> /home/lily/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/pyo3-0.17.3/src/instance.rs:641:52
    |
641 |     pub fn call1(&self, py: Python<'_>, args: impl IntoPy<Py<PyTuple>>) -> PyResult<PyObject> {
    |                                                    ^^^^^^^^^^^^^^^^^^^ required by this bound in `Py::<T>::call1`


error: aborting due to previous error==> ] 44/45: _kolo                                                          


For more information about this error, try `rustc --explain E0277`.

error: could not compile `_kolo` due to 2 previous errors
💥 maturin failed

Clearly I need to also convert _frame (a pyo3::ffi::PyFrameObject) into a type I can pass to python. I tried to convert it to a pyo3::types::PyFrame:

use pyo3::types::PyFrame;

extern "C" fn profile(
    _obj: *mut ffi::PyObject,
    _frame: *mut ffi::PyFrameObject,
    what: i32,
    _arg: *mut ffi::PyObject,
) -> i32 {
    if what == ffi::PyTrace_CALL {
        println!("Call");
        Python::with_gil(|py| {
            let obj = PyObject::from_owned_ptr_or_err(py, _obj);
            let frame = PyFrame::from_owned_ptr_or_err(py, _frame);
            let arg = PyObject::from_owned_ptr_or_err(py, _arg);
            let args = (frame.expect(""), "call", arg.expect(""));
            obj.expect("").call1(py, args);
        })
    } else if what == ffi::PyTrace_RETURN {
        println!("Return");
    }
    0
}

But this fails:

error[E0599]: no function or associated item named `from_owned_ptr_or_err` found for struct `PyFrame` in the current scope
  --> src/lib.rs:15:34
   |
15 |             let frame = PyFrame::from_owned_ptr_or_err(py, _frame);
   |                                  ^^^^^^^^^^^^^^^^^^^^^ function or associated item not found in `PyFrame`
   |
   = help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
   |
1  | use pyo3::FromPyPointer;
   |


error: aborting due to previous error==> ] 44/45: _kolo                                                          


For more information about this error, try `rustc --explain E0599`.

error: could not compile `_kolo` due to 2 previous errors
💥 maturin failed

Adding use pyo3::FromPyPointer as suggested does not fix things, but gives a different error:

error[E0308]: mismatched types=========> ] 44/45: _kolo                                                          
   --> src/lib.rs:16:60
    |
16  |             let frame = PyFrame::from_owned_ptr_or_err(py, _frame);
    |                         ------------------------------     ^^^^^^ expected struct `pyo3::ffi::PyObject`, found struct `PyFrameObject`
    |                         |
    |                         arguments to this function are incorrect
    |
    = note: expected raw pointer `*mut pyo3::ffi::PyObject`
               found raw pointer `*mut PyFrameObject`
note: associated function defined here
   --> /home/lily/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/pyo3-0.17.3/src/conversion.rs:546:15
    |
546 |     unsafe fn from_owned_ptr_or_err(py: Python<'p>, ptr: *mut ffi::PyObject) -> PyResult<&'p Self> {
    |               ^^^^^^^^^^^^^^^^^^^^^


error: aborting due to previous error==> ] 44/45: _kolo                                                          


For more information about this error, try `rustc --explain E0308`.

error: could not compile `_kolo` due to 2 previous errors
💥 maturin failed

At this point I'm stuck. Is there a straightforward way to convert the pyo3::ffi::PyFrameObject to a type suitable to pass to python? Or a way to convert pyo3::ffi::PyFrameObject to pyo3::fff::PyObject?

[birkenfeld]

PyFrameObject is a PyObject, so if you don't need a PyFrame on the Rust side the easiest here is to just take *mut PyObject in the callback or to cast the *mut PyFrameObject using as *mut PyObject inside of it.

[LilyFoote]

Casting with as *mut PyObject worked. Thanks!