add bindings for critical section API (#4477)

* add bindings for critical section API

* fix build on python < 3.13

* add release note

* fix clippy on gil-enabled 3.13 build

newsfragments/4477.added.md

@@ -0,0 +1 @@
+* Added bindings for the Python critical section API available on Python 3.13 and newer.

pyo3-ffi/src/cpython/critical_section.rs

@@ -0,0 +1,30 @@
+#[cfg(Py_GIL_DISABLED)]
+use crate::PyMutex;
+use crate::PyObject;
+
+#[repr(C)]
+#[cfg(Py_GIL_DISABLED)]
+pub struct PyCriticalSection {
+    _cs_prev: usize,
+    _cs_mutex: *mut PyMutex,
+}
+
+#[repr(C)]
+#[cfg(Py_GIL_DISABLED)]
+pub struct PyCriticalSection2 {
+    _cs_base: PyCriticalSection,
+    _cs_mutex2: *mut PyMutex,
+}
+
+#[cfg(not(Py_GIL_DISABLED))]
+opaque_struct!(PyCriticalSection);
+
+#[cfg(not(Py_GIL_DISABLED))]
+opaque_struct!(PyCriticalSection2);
+
+extern "C" {
+    pub fn PyCriticalSection_Begin(c: *mut PyCriticalSection, op: *mut PyObject);
+    pub fn PyCriticalSection_End(c: *mut PyCriticalSection);
+    pub fn PyCriticalSection2_Begin(c: *mut PyCriticalSection2, a: *mut PyObject, b: *mut PyObject);
+    pub fn PyCriticalSection2_End(c: *mut PyCriticalSection2);
+}

pyo3-ffi/src/cpython/mod.rs

@@ -5,6 +5,8 @@ pub(crate) mod bytesobject;
 pub(crate) mod ceval;
 pub(crate) mod code;
 pub(crate) mod compile;
+#[cfg(Py_3_13)]
+pub(crate) mod critical_section;
 pub(crate) mod descrobject;
 #[cfg(not(PyPy))]
 pub(crate) mod dictobject;
@@ -45,6 +47,8 @@ pub use self::bytesobject::*;
 pub use self::ceval::*;
 pub use self::code::*;
 pub use self::compile::*;
+#[cfg(Py_3_13)]
+pub use self::critical_section::*;
 pub use self::descrobject::*;
 #[cfg(not(PyPy))]
 pub use self::dictobject::*;