Opaque PyObject ABI support

Cargo.toml

@@ -116,7 +116,8 @@ abi3-py310 = ["abi3-py311", "pyo3-build-config/abi3-py310", "pyo3-ffi/abi3-py310
 abi3-py311 = ["abi3-py312", "pyo3-build-config/abi3-py311", "pyo3-ffi/abi3-py311"]
 abi3-py312 = ["abi3-py313", "pyo3-build-config/abi3-py312", "pyo3-ffi/abi3-py312"]
 abi3-py313 = ["abi3-py314", "pyo3-build-config/abi3-py313", "pyo3-ffi/abi3-py313"]
-abi3-py314 = ["abi3", "pyo3-build-config/abi3-py314", "pyo3-ffi/abi3-py314"]
+abi3-py314 = ["abi3-py315", "pyo3-build-config/abi3-py314", "pyo3-ffi/abi3-py314"]
+abi3-py315 = ["abi3", "pyo3-build-config/abi3-py315", "pyo3-ffi/abi3-py315"]
 
 # Automatically generates `python3.dll` import libraries for Windows targets.
 generate-import-lib = ["pyo3-ffi/generate-import-lib"]

guide/src/python-from-rust/calling-existing-code.md

@@ -154,6 +154,7 @@ mod foo {
     }
 }
 
+# #[cfg(not(_Py_OPAQUE_PYOBJECT))]
 fn main() -> PyResult<()> {
     pyo3::append_to_inittab!(foo);
     Python::attach(|py| Python::run(py, c"import foo; foo.add_one(6)", None, None))

newsfragments/5753.changed.md

@@ -0,0 +1 @@
+Module initialization uses the PyModExport and PyABIInfo APIs on python 3.15 and newer.

noxfile.py

@@ -82,10 +82,7 @@ def _supported_interpreter_versions(
 
 
 PY_VERSIONS = _supported_interpreter_versions("cpython")
-# We don't yet support abi3-py315 but do support cp315 and cp315t
-# version-specific builds
 ABI3_PY_VERSIONS = [p for p in PY_VERSIONS if not p.endswith("t")]
-ABI3_PY_VERSIONS.remove("3.15")
 PYPY_VERSIONS = _supported_interpreter_versions("pypy")
 
 
@@ -124,7 +121,12 @@ def test_rust(session: nox.Session):
         # We need to pass the feature set to the test command
         # so that it can be used in the test code
         # (e.g. for `#[cfg(feature = "abi3-py37")]`)
-        if feature_set and "abi3" in feature_set and FREE_THREADED_BUILD:
+        if (
+            feature_set
+            and "abi3" in feature_set
+            and FREE_THREADED_BUILD
+            and sys.version_info < (3, 15)
+        ):
             # free-threaded builds don't support abi3 yet
             continue
 

pyo3-build-config/Cargo.toml

@@ -41,7 +41,8 @@ abi3-py310 = ["abi3-py311"]
 abi3-py311 = ["abi3-py312"]
 abi3-py312 = ["abi3-py313"]
 abi3-py313 = ["abi3-py314"]
-abi3-py314 = ["abi3"]
+abi3-py314 = ["abi3-py315"]
+abi3-py315 = ["abi3"]
 
 [package.metadata.docs.rs]
 features = ["resolve-config"]

pyo3-build-config/src/impl_.rs

@@ -40,7 +40,7 @@ const MINIMUM_SUPPORTED_VERSION_GRAALPY: PythonVersion = PythonVersion {
 };
 
 /// Maximum Python version that can be used as minimum required Python version with abi3.
-pub(crate) const ABI3_MAX_MINOR: u8 = 14;
+pub(crate) const ABI3_MAX_MINOR: u8 = 15;
 
 #[cfg(test)]
 thread_local! {
@@ -190,8 +190,11 @@ impl InterpreterConfig {
         }
 
         // If Py_GIL_DISABLED is set, do not build with limited API support
-        if self.abi3 && !self.is_free_threaded() {
+        if self.abi3 && !(self.is_free_threaded()) {
             out.push("cargo:rustc-cfg=Py_LIMITED_API".to_owned());
+            if self.version.minor >= 15 {
+                out.push("cargo:rustc-cfg=_Py_OPAQUE_PYOBJECT".to_owned());
+            }
         }
 
         for flag in &self.build_flags.0 {
@@ -3203,6 +3206,31 @@ mod tests {
                 "cargo:rustc-cfg=Py_LIMITED_API".to_owned(),
             ]
         );
+
+        let interpreter_config = InterpreterConfig {
+            implementation: PythonImplementation::CPython,
+            version: PythonVersion {
+                major: 3,
+                minor: 15,
+            },
+            ..interpreter_config
+        };
+        assert_eq!(
+            interpreter_config.build_script_outputs(),
+            [
+                "cargo:rustc-cfg=Py_3_7".to_owned(),
+                "cargo:rustc-cfg=Py_3_8".to_owned(),
+                "cargo:rustc-cfg=Py_3_9".to_owned(),
+                "cargo:rustc-cfg=Py_3_10".to_owned(),
+                "cargo:rustc-cfg=Py_3_11".to_owned(),
+                "cargo:rustc-cfg=Py_3_12".to_owned(),
+                "cargo:rustc-cfg=Py_3_13".to_owned(),
+                "cargo:rustc-cfg=Py_3_14".to_owned(),
+                "cargo:rustc-cfg=Py_3_15".to_owned(),
+                "cargo:rustc-cfg=Py_LIMITED_API".to_owned(),
+                "cargo:rustc-cfg=_Py_OPAQUE_PYOBJECT".to_owned(),
+            ]
+        );
     }
 
     #[test]

pyo3-build-config/src/lib.rs

@@ -35,6 +35,7 @@ use target_lexicon::OperatingSystem;
 /// | ---- | ----------- |
 /// | `#[cfg(Py_3_7)]`, `#[cfg(Py_3_8)]`, `#[cfg(Py_3_9)]`, `#[cfg(Py_3_10)]` | These attributes mark code only for a given Python version and up. For example, `#[cfg(Py_3_7)]` marks code which can run on Python 3.7 **and newer**. |
 /// | `#[cfg(Py_LIMITED_API)]` | This marks code which is run when compiling with PyO3's `abi3` feature enabled. |
+/// | `#[cfg(Py_GIL_DISABLED)]` | This marks code which is run on the free-threaded interpreter. |
 /// | `#[cfg(PyPy)]` | This marks code which is run when compiling for PyPy. |
 /// | `#[cfg(GraalPy)]` | This marks code which is run when compiling for GraalPy. |
 ///
@@ -253,6 +254,7 @@ pub fn print_expected_cfgs() {
 
     println!("cargo:rustc-check-cfg=cfg(Py_LIMITED_API)");
     println!("cargo:rustc-check-cfg=cfg(Py_GIL_DISABLED)");
+    println!("cargo:rustc-check-cfg=cfg(_Py_OPAQUE_PYOBJECT)");
     println!("cargo:rustc-check-cfg=cfg(PyPy)");
     println!("cargo:rustc-check-cfg=cfg(GraalPy)");
     println!("cargo:rustc-check-cfg=cfg(py_sys_config, values(\"Py_DEBUG\", \"Py_REF_DEBUG\", \"Py_TRACE_REFS\", \"COUNT_ALLOCS\"))");

pyo3-ffi/Cargo.toml

@@ -33,7 +33,8 @@ abi3-py310 = ["abi3-py311", "pyo3-build-config/abi3-py310"]
 abi3-py311 = ["abi3-py312", "pyo3-build-config/abi3-py311"]
 abi3-py312 = ["abi3-py313", "pyo3-build-config/abi3-py312"]
 abi3-py313 = ["abi3-py314", "pyo3-build-config/abi3-py313"]
-abi3-py314 = ["abi3", "pyo3-build-config/abi3-py314"]
+abi3-py314 = ["abi3-py315", "pyo3-build-config/abi3-py314"]
+abi3-py315 = ["abi3", "pyo3-build-config/abi3-py315"]
 
 # Automatically generates `python3.dll` import libraries for Windows targets.
 generate-import-lib = ["pyo3-build-config/generate-import-lib"]

pyo3-ffi/src/moduleobject.rs

@@ -61,6 +61,7 @@ pub struct PyModuleDef_Base {
     pub m_copy: *mut PyObject,
 }
 
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[allow(
     clippy::declare_interior_mutable_const,
     reason = "contains atomic refcount on free-threaded builds"

pyo3-ffi/src/object.rs

@@ -1,11 +1,13 @@
 use crate::pyport::{Py_hash_t, Py_ssize_t};
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[cfg(Py_GIL_DISABLED)]
 use crate::refcount;
 #[cfg(Py_GIL_DISABLED)]
 use crate::PyMutex;
 use std::ffi::{c_char, c_int, c_uint, c_ulong, c_void};
 use std::mem;
 use std::ptr;
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[cfg(Py_GIL_DISABLED)]
 use std::sync::atomic::{AtomicIsize, AtomicU32};
 
@@ -92,6 +94,7 @@ const _PyObject_MIN_ALIGNMENT: usize = 4;
 // not currently possible to use constant variables with repr(align()), see
 // https://github.com/rust-lang/rust/issues/52840
 
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[cfg_attr(not(all(Py_3_15, Py_GIL_DISABLED)), repr(C))]
 #[cfg_attr(all(Py_3_15, Py_GIL_DISABLED), repr(C, align(4)))]
 #[derive(Debug)]
@@ -121,8 +124,10 @@ pub struct PyObject {
     pub ob_type: *mut PyTypeObject,
 }
 
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 const _: () = assert!(std::mem::align_of::<PyObject>() >= _PyObject_MIN_ALIGNMENT);
 
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[allow(
     clippy::declare_interior_mutable_const,
     reason = "contains atomic refcount on free-threaded builds"
@@ -157,10 +162,14 @@ pub const PyObject_HEAD_INIT: PyObject = PyObject {
     ob_type: std::ptr::null_mut(),
 };
 
+#[cfg(_Py_OPAQUE_PYOBJECT)]
+opaque_struct!(pub PyObject);
+
 // skipped _Py_UNOWNED_TID
 
 // skipped _PyObject_CAST
 
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[repr(C)]
 #[derive(Debug)]
 pub struct PyVarObject {
@@ -172,6 +181,9 @@ pub struct PyVarObject {
     pub _ob_size_graalpy: Py_ssize_t,
 }
 
+#[cfg(_Py_OPAQUE_PYOBJECT)]
+opaque_struct!(pub PyVarObject);
+
 // skipped private _PyVarObject_CAST
 
 #[inline]
@@ -219,6 +231,16 @@ extern "C" {
     pub fn Py_TYPE(ob: *mut PyObject) -> *mut PyTypeObject;
 }
 
+#[cfg_attr(windows, link(name = "pythonXY"))]
+#[cfg(all(Py_LIMITED_API, Py_3_15))]
+extern "C" {
+    #[cfg_attr(PyPy, link_name = "PyPy_SIZE")]
+    pub fn Py_SIZE(ob: *mut PyObject) -> Py_ssize_t;
+    #[cfg_attr(PyPy, link_name = "PyPy_IS_TYPE")]
+    pub fn Py_IS_TYPE(ob: *mut PyObject, tp: *mut PyTypeObject) -> c_int;
+    // skipped Py_SET_SIZE
+}
+
 // skip _Py_TYPE compat shim
 
 #[cfg_attr(windows, link(name = "pythonXY"))]
@@ -229,6 +251,7 @@ extern "C" {
     pub static mut PyBool_Type: PyTypeObject;
 }
 
+#[cfg(not(all(Py_LIMITED_API, Py_3_15)))]
 #[inline]
 pub unsafe fn Py_SIZE(ob: *mut PyObject) -> Py_ssize_t {
     #[cfg(not(GraalPy))]
@@ -241,6 +264,7 @@ pub unsafe fn Py_SIZE(ob: *mut PyObject) -> Py_ssize_t {
     _Py_SIZE(ob)
 }
 
+#[cfg(not(all(Py_LIMITED_API, Py_3_15)))]
 #[inline]
 pub unsafe fn Py_IS_TYPE(ob: *mut PyObject, tp: *mut PyTypeObject) -> c_int {
     (Py_TYPE(ob) == tp) as c_int

pyo3-ffi/src/refcount.rs

@@ -1,6 +1,6 @@
 use crate::pyport::Py_ssize_t;
 use crate::PyObject;
-#[cfg(py_sys_config = "Py_REF_DEBUG")]
+#[cfg(all(not(Py_LIMITED_API), py_sys_config = "Py_REF_DEBUG"))]
 use std::ffi::c_char;
 #[cfg(Py_3_12)]
 use std::ffi::c_int;
@@ -11,7 +11,7 @@ use std::ffi::c_uint;
 #[cfg(all(Py_3_14, not(Py_GIL_DISABLED)))]
 use std::ffi::c_ulong;
 use std::ptr;
-#[cfg(Py_GIL_DISABLED)]
+#[cfg(all(Py_GIL_DISABLED, not(Py_LIMITED_API)))]
 use std::sync::atomic::Ordering::Relaxed;
 
 #[cfg(all(Py_3_14, not(Py_3_15)))]
@@ -116,6 +116,7 @@ pub unsafe fn Py_REFCNT(ob: *mut PyObject) -> Py_ssize_t {
     }
 }
 
+#[cfg(not(_Py_OPAQUE_PYOBJECT))]
 #[cfg(Py_3_12)]
 #[inline(always)]
 unsafe fn _Py_IsImmortal(op: *mut PyObject) -> c_int {

pyo3-macros-backend/src/module.rs

@@ -511,6 +511,7 @@ fn module_initialization(
 ) -> TokenStream {
     let Ctx { pyo3_path, .. } = ctx;
     let pyinit_symbol = format!("PyInit_{name}");
+    let pymodexport_symbol = format!("PyModExport_{name}");
     let pyo3_name = LitCStr::new(&CString::new(full_name).unwrap(), Span::call_site());
 
     let mut result = quote! {
@@ -531,24 +532,39 @@ fn module_initialization(
                 #pyo3_path::impl_::trampoline::module_exec(module, #module_exec)
             }
 
-            static SLOTS: impl_::PyModuleSlots<4> = impl_::PyModuleSlotsBuilder::new()
+            // The full slots, used for the PyModExport initializaiton
+            static SLOTS: impl_::PyModuleSlots = impl_::PyModuleSlotsBuilder::new()
                 .with_mod_exec(__pyo3_module_exec)
                 .with_gil_used(#gil_used)
+                .with_name(__PYO3_NAME)
+                .with_doc(#doc)
                 .build();
 
+            // Since the macros need to be written agnostic to the Python version
+            // we need to explicitly pass the name and docstring for PyModuleDef
+            // initializaiton.
             impl_::ModuleDef::new(__PYO3_NAME, #doc, &SLOTS)
         };
     };
     if !is_submodule {
         result.extend(quote! {
             /// This autogenerated function is called by the python interpreter when importing
-            /// the module.
+            /// the module on Python 3.14 and older.
             #[doc(hidden)]
             #[export_name = #pyinit_symbol]
             pub unsafe extern "C" fn __pyo3_init() -> *mut #pyo3_path::ffi::PyObject {
                 _PYO3_DEF.init_multi_phase()
             }
         });
+        result.extend(quote! {
+            /// This autogenerated function is called by the python interpreter when importing
+            /// the module on Python 3.15 and newer.
+            #[doc(hidden)]
+            #[export_name = #pymodexport_symbol]
+            pub unsafe extern "C" fn __pyo3_export() -> *mut #pyo3_path::ffi::PyModuleDef_Slot {
+                _PYO3_DEF.get_slots()
+            }
+        });
     }
     result
 }

src/impl_/pyclass.rs

@@ -1484,7 +1484,7 @@ mod tests {
                     (offset_of!(ExpectedLayout, contents) + offset_of!(FrozenClass, value))
                         as ffi::Py_ssize_t
                 );
-                assert_eq!(member.flags, ffi::Py_READONLY);
+                assert_eq!(member.flags & ffi::Py_READONLY, ffi::Py_READONLY);
             }
             _ => panic!("Expected a StructMember"),
         }
@@ -1593,17 +1593,17 @@ mod tests {
         // SAFETY: def.doc originated from a CStr
         assert_eq!(unsafe { CStr::from_ptr(def.doc) }, c"My field doc");
         assert_eq!(def.type_code, ffi::Py_T_OBJECT_EX);
-        #[allow(irrefutable_let_patterns)]
-        let PyObjectOffset::Absolute(contents_offset) =
-            <MyClass as PyClassImpl>::Layout::CONTENTS_OFFSET
-        else {
-            panic!()
+        #[allow(clippy::infallible_destructuring_match)]
+        let contents_offset = match <MyClass as PyClassImpl>::Layout::CONTENTS_OFFSET {
+            PyObjectOffset::Absolute(contents_offset) => contents_offset,
+            #[cfg(Py_3_12)]
+            PyObjectOffset::Relative(contents_offset) => contents_offset,
         };
         assert_eq!(
             def.offset,
             contents_offset + FIELD_OFFSET as ffi::Py_ssize_t
         );
-        assert_eq!(def.flags, ffi::Py_READONLY);
+        assert_eq!(def.flags & ffi::Py_READONLY, ffi::Py_READONLY);
     }
 
     #[test]