update FFI definitions in objimpl.h to not expose private symbols (#5591)

* update FFI definitions in `objimpl.h` to not expose private variables

* newsfragments

* Apply suggestions from code review

Co-authored-by: Icxolu <[email protected]>

---------

Co-authored-by: Icxolu <[email protected]>

Author: davidhewitt

newsfragments/5591.added.md

@@ -0,0 +1 @@
+Add FFI definitions `PyObject_New`, `PyObject_NewVar`, `PyObject_GC_Resize`, `PyObject_GC_New`, and `PyObject_GC_NewVar`.

newsfragments/5591.removed.md

@@ -0,0 +1 @@
+Remove private FFI definitions `_PyObject_New`, `_PyObject_NewVar`, `_PyObject_GC_Resize`, `_PyObject_GC_New`, and `_PyObject_GC_NewVar`.

pyo3-ffi/src/objimpl.rs

@@ -33,15 +33,27 @@ extern "C" {
     // skipped PyObject_INIT_VAR
 
     #[cfg_attr(PyPy, link_name = "_PyPyObject_New")]
-    pub fn _PyObject_New(arg1: *mut PyTypeObject) -> *mut PyObject;
+    fn _PyObject_New(typeobj: *mut PyTypeObject) -> *mut PyObject;
     #[cfg_attr(PyPy, link_name = "_PyPyObject_NewVar")]
-    pub fn _PyObject_NewVar(arg1: *mut PyTypeObject, arg2: Py_ssize_t) -> *mut PyVarObject;
+    fn _PyObject_NewVar(typeobj: *mut PyTypeObject, n: Py_ssize_t) -> *mut PyVarObject;
+}
+
+#[inline]
+pub unsafe fn PyObject_New<T>(typeobj: *mut PyTypeObject) -> *mut T {
+    _PyObject_New(typeobj).cast()
+}
+
+// skipped PyObject_NEW
+
+#[inline]
+pub unsafe fn PyObject_NewVar<T>(typeobj: *mut PyTypeObject, n: Py_ssize_t) -> *mut T {
+    _PyObject_NewVar(typeobj, n).cast()
+}
 
-    // skipped PyObject_New
-    // skipped PyObject_NEW
-    // skipped PyObject_NewVar
-    // skipped PyObject_NEW_VAR
+// skipped PyObject_NEW_VAR
 
+extern "C" {
+    #[cfg_attr(PyPy, link_name = "PyPyGC_Collect")]
     pub fn PyGC_Collect() -> Py_ssize_t;
 
     #[cfg(Py_3_10)]
@@ -55,8 +67,6 @@ extern "C" {
     #[cfg(Py_3_10)]
     #[cfg_attr(PyPy, link_name = "PyPyGC_IsEnabled")]
     pub fn PyGC_IsEnabled() -> c_int;
-
-    // skipped PyUnstable_GC_VisitObjects
 }
 
 #[inline]
@@ -65,24 +75,41 @@ pub unsafe fn PyType_IS_GC(t: *mut PyTypeObject) -> c_int {
 }
 
 extern "C" {
-    pub fn _PyObject_GC_Resize(arg1: *mut PyVarObject, arg2: Py_ssize_t) -> *mut PyVarObject;
+    fn _PyObject_GC_Resize(op: *mut PyVarObject, n: Py_ssize_t) -> *mut PyVarObject;
+}
 
-    // skipped PyObject_GC_Resize
+#[inline]
+pub unsafe fn PyObject_GC_Resize<T>(op: *mut PyObject, n: Py_ssize_t) -> *mut T {
+    _PyObject_GC_Resize(op.cast(), n).cast()
+}
 
+extern "C" {
     #[cfg_attr(PyPy, link_name = "_PyPyObject_GC_New")]
-    pub fn _PyObject_GC_New(arg1: *mut PyTypeObject) -> *mut PyObject;
+    fn _PyObject_GC_New(typeobj: *mut PyTypeObject) -> *mut PyObject;
     #[cfg_attr(PyPy, link_name = "_PyPyObject_GC_NewVar")]
-    pub fn _PyObject_GC_NewVar(arg1: *mut PyTypeObject, arg2: Py_ssize_t) -> *mut PyVarObject;
+    fn _PyObject_GC_NewVar(typeobj: *mut PyTypeObject, n: Py_ssize_t) -> *mut PyVarObject;
+
     #[cfg(not(PyPy))]
     pub fn PyObject_GC_Track(arg1: *mut c_void);
+
     #[cfg(not(PyPy))]
     pub fn PyObject_GC_UnTrack(arg1: *mut c_void);
+
     #[cfg_attr(PyPy, link_name = "PyPyObject_GC_Del")]
     pub fn PyObject_GC_Del(arg1: *mut c_void);
+}
 
-    // skipped PyObject_GC_New
-    // skipped PyObject_GC_NewVar
+#[inline]
+pub unsafe fn PyObject_GC_New<T>(typeobj: *mut PyTypeObject) -> *mut T {
+    _PyObject_GC_New(typeobj).cast()
+}
+
+#[inline]
+pub unsafe fn PyObject_GC_NewVar<T>(typeobj: *mut PyTypeObject, n: Py_ssize_t) -> *mut T {
+    _PyObject_GC_NewVar(typeobj, n).cast()
+}
 
+extern "C" {
     #[cfg(any(all(Py_3_9, not(PyPy)), Py_3_10))] // added in 3.9, or 3.10 on PyPy
     #[cfg_attr(PyPy, link_name = "PyPyObject_GC_IsTracked")]
     pub fn PyObject_GC_IsTracked(arg1: *mut PyObject) -> c_int;