rust-cpython: fix signature of make_dirstate_tuple()

Fortunately, the layout of PyObject {} is compatible with a C pointer, but
we shouldn't rely on that. This also fixes the handling of NULL pointer.

rust/hg-cpython/src/dirstate.rs

@@ -1,130 +1,132
 // dirstate.rs
 //
 // Copyright 2019 Raphaël Gomès <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Bindings for the `hg::dirstate` module provided by the
 //! `hg-core` package.
 //!
 //! From Python, this will be seen as `mercurial.rustext.dirstate`
 mod copymap;
 mod dirs_multiset;
 mod dirstate_map;
 use crate::dirstate::{dirs_multiset::Dirs, dirstate_map::DirstateMap};
 use cpython::{
     exc, PyBytes, PyDict, PyErr, PyModule, PyObject, PyResult, PySequence,
     Python,
 };
 use hg::{
     utils::hg_path::HgPathBuf, DirstateEntry, DirstateParseError, EntryState,
     StateMap,
 };
 use libc::{c_char, c_int};
 #[cfg(feature = "python27")]
-use python27_sys::PyCapsule_Import;
+use python27_sys as python_sys;
 #[cfg(feature = "python3")]
-use python3_sys::PyCapsule_Import;
+use python3_sys as python_sys;
+use python_sys::PyCapsule_Import;
 use std::convert::TryFrom;
 use std::ffi::CStr;
 use std::mem::transmute;
 
 /// C code uses a custom `dirstate_tuple` type, checks in multiple instances
 /// for this type, and raises a Python `Exception` if the check does not pass.
 /// Because this type differs only in name from the regular Python tuple, it
 /// would be a good idea in the near future to remove it entirely to allow
 /// for a pure Python tuple of the same effective structure to be used,
 /// rendering this type and the capsule below useless.
 type MakeDirstateTupleFn = unsafe extern "C" fn(
     state: c_char,
     mode: c_int,
     size: c_int,
     mtime: c_int,
-) -> PyObject;
+) -> *mut python_sys::PyObject;
 
 /// This is largely a copy/paste from cindex.rs, pending the merge of a
 /// `py_capsule_fn!` macro in the rust-cpython project:
 /// https://github.com/dgrunwald/rust-cpython/pull/169
 fn decapsule_make_dirstate_tuple(py: Python) -> PyResult<MakeDirstateTupleFn> {
     unsafe {
         let caps_name = CStr::from_bytes_with_nul_unchecked(
             b"mercurial.cext.parsers.make_dirstate_tuple_CAPI\0",
         );
         let from_caps = PyCapsule_Import(caps_name.as_ptr(), 0);
         if from_caps.is_null() {
             return Err(PyErr::fetch(py));
         }
         Ok(transmute(from_caps))
     }
 }
 
 pub fn make_dirstate_tuple(
     py: Python,
     entry: &DirstateEntry,
 ) -> PyResult<PyObject> {
     let make = decapsule_make_dirstate_tuple(py)?;
 
     let &DirstateEntry {
         state,
         mode,
         size,
         mtime,
     } = entry;
     // Explicitly go through u8 first, then cast to platform-specific `c_char`
     // because Into<u8> has a specific implementation while `as c_char` would
     // just do a naive enum cast.
     let state_code: u8 = state.into();
 
-    unsafe {
+    let maybe_obj = unsafe {
         let ptr = make(state_code as c_char, mode, size, mtime);
-        Ok(ptr)
-    }
+        PyObject::from_owned_ptr_opt(py, ptr)
+    };
+    maybe_obj.ok_or_else(|| PyErr::fetch(py))
 }
 
 pub fn extract_dirstate(py: Python, dmap: &PyDict) -> Result<StateMap, PyErr> {
     dmap.items(py)
         .iter()
         .map(|(filename, stats)| {
             let stats = stats.extract::<PySequence>(py)?;
             let state = stats.get_item(py, 0)?.extract::<PyBytes>(py)?;
             let state = EntryState::try_from(state.data(py)[0]).map_err(
                 |e: DirstateParseError| {
                     PyErr::new::<exc::ValueError, _>(py, e.to_string())
                 },
             )?;
             let mode = stats.get_item(py, 1)?.extract(py)?;
             let size = stats.get_item(py, 2)?.extract(py)?;
             let mtime = stats.get_item(py, 3)?.extract(py)?;
             let filename = filename.extract::<PyBytes>(py)?;
             let filename = filename.data(py);
             Ok((
                 HgPathBuf::from(filename.to_owned()),
                 DirstateEntry {
                     state,
                     mode,
                     size,
                     mtime,
                 },
             ))
         })
         .collect()
 }
 
 /// Create the module, with `__package__` given from parent
 pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
     let dotted_name = &format!("{}.dirstate", package);
     let m = PyModule::new(py, dotted_name)?;
 
     m.add(py, "__package__", package)?;
     m.add(py, "__doc__", "Dirstate - Rust implementation")?;
 
     m.add_class::<Dirs>(py)?;
     m.add_class::<DirstateMap>(py)?;
 
     let sys = PyModule::import(py, "sys")?;
     let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
     sys_modules.set_item(py, dotted_name, &m)?;
 
     Ok(m)
 }