Add Py_IncRef, Py_DecRef, Py_XNewRef (#8726)

crates/capi/src/refcount.rs

@@ -2,12 +2,26 @@ use crate::{PyObject, pystate::with_vm};
 use core::ptr::NonNull;
 use rustpython_vm::PyObjectRef;
 
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn Py_DecRef(op: *mut PyObject) {
+    if !op.is_null() {
+        unsafe { _Py_DecRef(op) }
+    }
+}
+
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn _Py_DecRef(op: *mut PyObject) {
     // By dropping PyObjectRef, we will decrement the reference count.
     unsafe { drop(PyObjectRef::from_raw(NonNull::new_unchecked(op))) };
 }
 
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn Py_IncRef(op: *mut PyObject) {
+    if !op.is_null() {
+        unsafe { _Py_IncRef(op) }
+    }
+}
+
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn _Py_IncRef(op: *mut PyObject) {
     // Don't drop the owned value, as we just want to increment the refcount.
@@ -19,6 +33,15 @@ pub unsafe extern "C" fn Py_NewRef(op: *mut PyObject) -> *mut PyObject {
     with_vm(|_vm| unsafe { (*op).to_owned() })
 }
 
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn Py_XNewRef(op: *mut PyObject) -> *mut PyObject {
+    if op.is_null() {
+        core::ptr::null_mut()
+    } else {
+        unsafe { Py_NewRef(op) }
+    }
+}
+
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn Py_REFCNT(op: *mut PyObject) -> isize {
     with_vm(|_vm| unsafe { &*op }.strong_count())
@@ -45,4 +68,12 @@ mod tests {
             assert_eq!(ffi::Py_REFCNT(obj.as_ptr()), ref_count);
         });
     }
+
+    #[test]
+    fn incdec_null_is_noop() {
+        unsafe {
+            ffi::Py_IncRef(core::ptr::null_mut());
+            ffi::Py_DecRef(core::ptr::null_mut());
+        }
+    }
 }