Add non-limited PyCellObject interface (#5978)

* Implement PyCellObject and associated functions

Add PyCellObject structure and related functions.

* Add cellobject module to lib.rs

* news

* Update lib.rs

* spelling

Co-authored-by: Thomas Tanon <thomas@pellissier-tanon.fr>

* Drop macro

Co-authored-by: Thomas Tanon <thomas@pellissier-tanon.fr>

* fmt

* Define in `src/cpython/mod.rs`, not `src/lib.rs`

---------

Co-authored-by: Thomas Tanon <thomas@pellissier-tanon.fr>

Author: clin1234

newsfragments/5978.added.md

@@ -0,0 +1 @@
+Add non-limited API version of `PyCellObject` and associated functions.

pyo3-ffi/src/cpython/cellobject.rs

@@ -0,0 +1,24 @@
+use crate::object::*;
+use std::ffi::c_int;
+
+#[cfg(not(any(PyPy, GraalPy)))]
+#[repr(C)]
+pub struct PyCellObject {
+    pub ob_base: PyObject,
+    pub ob_ref: *mut PyObject,
+}
+
+extern_libpython! {
+    pub fn PyCell_New(o: *mut PyObject) -> *mut PyObject;
+    pub fn PyCell_Get(o: *mut PyObject) -> *mut PyObject;
+    pub fn PyCell_Set(o: *mut PyObject, val: *mut PyObject) -> *mut PyObject;
+    pub static mut PyCell_Type: PyTypeObject;
+}
+
+#[inline]
+pub unsafe fn PyCell_Check(op: *mut PyObject) -> c_int {
+    Py_IS_TYPE(op, &raw mut PyCell_Type)
+}
+
+// skipped PyCell_SET
+// skipped PyCell_GET

pyo3-ffi/src/cpython/mod.rs

@@ -1,6 +1,7 @@
 pub(crate) mod abstract_;
 pub(crate) mod bytearrayobject;
 pub(crate) mod bytesobject;
+pub(crate) mod cellobject;
 #[cfg(not(PyPy))]
 pub(crate) mod ceval;
 pub(crate) mod code;
@@ -48,6 +49,7 @@ pub(crate) mod weakrefobject;
 pub use self::abstract_::*;
 pub use self::bytearrayobject::*;
 pub use self::bytesobject::*;
+pub use self::cellobject::*;
 #[cfg(not(PyPy))]
 pub use self::ceval::*;
 pub use self::code::*;