Merge pull request #994 from scalexm/ptr

`LazyStaticType::get_or_init` returns an `*mut` instead of a `&` ref

guide/src/class.md

@@ -927,7 +927,7 @@ unsafe impl pyo3::PyTypeInfo for MyClass {
     const FLAGS: usize = 0;
 
     #[inline]
-    fn type_object_raw(py: pyo3::Python) -> &'static pyo3::ffi::PyTypeObject {
+    fn type_object_raw(py: pyo3::Python) -> *mut pyo3::ffi::PyTypeObject {
         use pyo3::type_object::LazyStaticType;
         static TYPE_OBJECT: LazyStaticType = LazyStaticType::new();
         TYPE_OBJECT.get_or_init::<Self>(py)

pyo3-derive-backend/src/pyclass.rs

@@ -401,7 +401,7 @@ fn impl_class(
             const FLAGS: usize = #(#flags)|* | #extended;
 
             #[inline]
-            fn type_object_raw(py: pyo3::Python) -> &'static pyo3::ffi::PyTypeObject {
+            fn type_object_raw(py: pyo3::Python) -> *mut pyo3::ffi::PyTypeObject {
                 use pyo3::type_object::LazyStaticType;
                 static TYPE_OBJECT: LazyStaticType = LazyStaticType::new();
                 TYPE_OBJECT.get_or_init::<Self>(py)

src/freelist.rs

@@ -72,9 +72,8 @@ where
     T: PyTypeInfo + PyClassWithFreeList,
 {
     unsafe fn new(py: Python, subtype: *mut ffi::PyTypeObject) -> *mut Self::Layout {
-        let type_obj = Self::type_object_raw(py) as *const _ as _;
         // if subtype is not equal to this type, we cannot use the freelist
-        if subtype == type_obj {
+        if subtype == Self::type_object_raw(py) {
             if let Some(obj) = <Self as PyClassWithFreeList>::get_free_list().pop() {
                 ffi::PyObject_Init(obj, subtype);
                 return obj as _;

src/pyclass.rs

@@ -18,7 +18,7 @@ pub(crate) unsafe fn default_new<T: PyTypeInfo>(
     // if the class derives native types(e.g., PyDict), call special new
     if T::FLAGS & type_flags::EXTENDED != 0 && T::BaseLayout::IS_NATIVE_TYPE {
         let base_tp = T::BaseType::type_object_raw(py);
-        if let Some(base_new) = base_tp.tp_new {
+        if let Some(base_new) = (*base_tp).tp_new {
             return base_new(subtype, ptr::null_mut(), ptr::null_mut());
         }
     }
@@ -122,7 +122,7 @@ where
         s => CString::new(s)?.into_raw(),
     };
 
-    type_object.tp_base = T::BaseType::type_object_raw(py) as *const _ as _;
+    type_object.tp_base = T::BaseType::type_object_raw(py);
 
     type_object.tp_name = match module_name {
         Some(module_name) => CString::new(format!("{}.{}", module_name, T::NAME))?.into_raw(),

src/pyclass_init.rs

@@ -122,7 +122,7 @@ impl<T: PyClass> PyClassInitializer<T> {
         T: PyClass,
         T::BaseLayout: PyBorrowFlagLayout<T::BaseType>,
     {
-        unsafe { self.create_cell_from_subtype(py, T::type_object_raw(py) as *const _ as _) }
+        unsafe { self.create_cell_from_subtype(py, T::type_object_raw(py)) }
     }
 
     /// Create a new PyCell and initialize it given a typeobject `subtype`.

src/type_object.rs

@@ -101,21 +101,16 @@ pub unsafe trait PyTypeInfo: Sized {
     type AsRefTarget: crate::PyNativeType;
 
     /// PyTypeObject instance for this type.
-    fn type_object_raw(py: Python) -> &'static ffi::PyTypeObject;
+    fn type_object_raw(py: Python) -> *mut ffi::PyTypeObject;
 
     /// Check if `*mut ffi::PyObject` is instance of this type
     fn is_instance(object: &PyAny) -> bool {
-        unsafe {
-            ffi::PyObject_TypeCheck(
-                object.as_ptr(),
-                Self::type_object(object.py()) as *const _ as _,
-            ) != 0
-        }
+        unsafe { ffi::PyObject_TypeCheck(object.as_ptr(), Self::type_object_raw(object.py())) != 0 }
     }
 
     /// Check if `*mut ffi::PyObject` is exact instance of this type
     fn is_exact_instance(object: &PyAny) -> bool {
-        unsafe { (*object.as_ptr()).ob_type == Self::type_object(object.py()) as *const _ as _ }
+        unsafe { (*object.as_ptr()).ob_type == Self::type_object_raw(object.py()) }
     }
 }
 
@@ -135,7 +130,7 @@ where
     T: PyTypeInfo,
 {
     fn type_object(py: Python) -> &PyType {
-        unsafe { py.from_borrowed_ptr(Self::type_object_raw(py) as *const _ as _) }
+        unsafe { py.from_borrowed_ptr(Self::type_object_raw(py) as _) }
     }
 }
 
@@ -143,7 +138,7 @@ where
 #[doc(hidden)]
 pub struct LazyStaticType {
     // Boxed because Python expects the type object to have a stable address.
-    value: GILOnceCell<Box<ffi::PyTypeObject>>,
+    value: GILOnceCell<*mut ffi::PyTypeObject>,
     // Threads which have begun initialization. Used for reentrant initialization detection.
     initializing_threads: Mutex<Vec<ThreadId>>,
 }
@@ -156,42 +151,38 @@ impl LazyStaticType {
         }
     }
 
-    pub fn get_or_init<T: PyClass>(&self, py: Python) -> &ffi::PyTypeObject {
-        self.value
-            .get_or_init(py, || {
-                {
-                    // Code evaluated at class init time, such as class attributes, might lead to
-                    // recursive initalization of the type object if the class attribute is the same
-                    // type as the class.
-                    //
-                    // That could lead to all sorts of unsafety such as using incomplete type objects
-                    // to initialize class instances, so recursive initialization is prevented.
-                    let thread_id = thread::current().id();
-                    let mut threads = self.initializing_threads.lock();
-                    if threads.contains(&thread_id) {
-                        panic!("Recursive initialization of type_object for {}", T::NAME);
-                    } else {
-                        threads.push(thread_id)
-                    }
+    pub fn get_or_init<T: PyClass>(&self, py: Python) -> *mut ffi::PyTypeObject {
+        *self.value.get_or_init(py, || {
+            {
+                // Code evaluated at class init time, such as class attributes, might lead to
+                // recursive initalization of the type object if the class attribute is the same
+                // type as the class.
+                //
+                // That could lead to all sorts of unsafety such as using incomplete type objects
+                // to initialize class instances, so recursive initialization is prevented.
+                let thread_id = thread::current().id();
+                let mut threads = self.initializing_threads.lock();
+                if threads.contains(&thread_id) {
+                    panic!("Recursive initialization of type_object for {}", T::NAME);
+                } else {
+                    threads.push(thread_id)
                 }
+            }
 
-                // Okay, not recursive initialization - can proceed safely.
-                let mut type_object = Box::new(ffi::PyTypeObject_INIT);
+            // Okay, not recursive initialization - can proceed safely.
+            let mut type_object = Box::new(ffi::PyTypeObject_INIT);
 
-                initialize_type_object::<T>(py, T::MODULE, type_object.as_mut()).unwrap_or_else(
-                    |e| {
-                        e.print(py);
-                        panic!("An error occurred while initializing class {}", T::NAME)
-                    },
-                );
+            initialize_type_object::<T>(py, T::MODULE, type_object.as_mut()).unwrap_or_else(|e| {
+                e.print(py);
+                panic!("An error occurred while initializing class {}", T::NAME)
+            });
 
-                // Initialization successfully complete, can clear the thread list.
-                // (No futher calls to get_or_init() will try to init, on any thread.)
-                *self.initializing_threads.lock() = Vec::new();
+            // Initialization successfully complete, can clear the thread list.
+            // (No futher calls to get_or_init() will try to init, on any thread.)
+            *self.initializing_threads.lock() = Vec::new();
 
-                type_object
-            })
-            .as_ref()
+            Box::into_raw(type_object)
+        })
     }
 }
 

src/types/mod.rs

@@ -143,8 +143,11 @@ macro_rules! pyobject_native_type_convert(
             const MODULE: Option<&'static str> = $module;
 
             #[inline]
-            fn type_object_raw(_py: Python) -> &'static $crate::ffi::PyTypeObject {
-                unsafe{ &$typeobject }
+            fn type_object_raw(_py: Python) -> *mut $crate::ffi::PyTypeObject {
+                // Create a very short lived mutable reference and directly
+                // cast it to a pointer: no mutable references can be aliasing
+                // because we hold the GIL.
+                unsafe { &mut $typeobject }
             }
 
             #[allow(unused_unsafe)]