ci: Add 3.15 in CI

.github/workflows/ci.yml

@@ -234,6 +234,8 @@ jobs:
             "3.13t",
             "3.14",
             "3.14t",
+            "3.15-dev",
+            "3.15t-dev",
             "pypy3.11",
             "graalpy25.0",
           ]

newsfragments/5518-packaging.md

@@ -0,0 +1 @@
+Add 3.15 to CI for preliminary testing

noxfile.py

@@ -82,6 +82,10 @@ 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")
 
 
@@ -959,14 +963,16 @@ def test_version_limits(session: nox.Session):
         config_file.set("CPython", "3.6")
         _run_cargo(session, "check", env=env, expect_error=True)
 
-        assert "3.15" not in PY_VERSIONS
-        config_file.set("CPython", "3.15")
+        assert "3.16" not in PY_VERSIONS
+        config_file.set("CPython", "3.16")
         _run_cargo(session, "check", env=env, expect_error=True)
 
-        # 3.15 CPython should build if abi3 is explicitly requested
+        # 3.16 CPython should build if abi3 is explicitly requested
         _run_cargo(session, "check", "--features=pyo3/abi3", env=env)
 
         # 3.15 CPython should build with forward compatibility
+        # TODO: check on 3.16 when adding abi3-py315 support
+        config_file.set("CPython", "3.15")
         env["PYO3_USE_ABI3_FORWARD_COMPATIBILITY"] = "1"
         _run_cargo(session, "check", env=env)
 
@@ -976,7 +982,7 @@ def test_version_limits(session: nox.Session):
 
     # attempt to build with latest version and check that abi3 version
     # configured matches the feature
-    max_minor_version = max(int(v.split(".")[1]) for v in PY_VERSIONS if "t" not in v)
+    max_minor_version = max(int(v.split(".")[1]) for v in ABI3_PY_VERSIONS)
     with tempfile.TemporaryFile() as stderr:
         env = os.environ.copy()
         env["PYO3_PRINT_CONFIG"] = "1"  # get diagnostics from the build
@@ -1010,7 +1016,7 @@ def check_feature_powerset(session: nox.Session):
 
     # free-threaded builds do not support ABI3 (yet)
     EXPECTED_ABI3_FEATURES = {
-        f"abi3-py3{ver.split('.')[1]}" for ver in PY_VERSIONS if not ver.endswith("t")
+        f"abi3-py3{ver.split('.')[1]}" for ver in ABI3_PY_VERSIONS
     }
 
     EXCLUDED_FROM_FULL = {

pyo3-ffi/Cargo.toml

@@ -49,7 +49,7 @@ workspace = true
 
 [package.metadata.cpython]
 min-version = "3.7"
-max-version = "3.14" # inclusive
+max-version = "3.15" # inclusive
 
 [package.metadata.pypy]
 min-version = "3.11"

pyo3-ffi/build.rs

@@ -18,7 +18,7 @@ const SUPPORTED_VERSIONS_CPYTHON: SupportedVersions = SupportedVersions {
     min: PythonVersion { major: 3, minor: 7 },
     max: PythonVersion {
         major: 3,
-        minor: 14,
+        minor: 15,
     },
 };
 

pyo3-ffi/src/bytearrayobject.rs

@@ -14,6 +14,8 @@ pub struct PyByteArrayObject {
     pub ob_exports: Py_ssize_t,
     #[cfg(not(Py_3_9))]
     pub ob_exports: c_int,
+    #[cfg(Py_3_15)]
+    pub ob_bytes_object: *mut PyObject,
 }
 
 #[cfg(any(PyPy, GraalPy, Py_LIMITED_API))]

pyo3-ffi/src/object.rs

@@ -49,6 +49,13 @@ pub struct PyObjectObFlagsAndRefcnt {
     pub ob_flags: u16,
 }
 
+// 4-byte alignment comes from value of _PyObject_MIN_ALIGNMENT
+
+#[cfg(all(not(Py_GIL_DISABLED), Py_3_15))]
+#[repr(C, align(4))]
+#[derive(Copy, Clone)]
+struct Aligner(c_char);
+
 #[repr(C)]
 #[derive(Copy, Clone)]
 #[cfg(all(Py_3_12, not(Py_GIL_DISABLED)))]
@@ -62,6 +69,8 @@ pub union PyObjectObRefcnt {
     pub ob_refcnt: Py_ssize_t,
     #[cfg(all(target_pointer_width = "64", not(Py_3_14)))]
     pub ob_refcnt_split: [crate::PY_UINT32_T; 2],
+    #[cfg(all(not(Py_GIL_DISABLED), Py_3_15))]
+    _aligner: Aligner,
 }
 
 #[cfg(all(Py_3_12, not(Py_GIL_DISABLED)))]
@@ -74,10 +83,17 @@ impl std::fmt::Debug for PyObjectObRefcnt {
 #[cfg(all(not(Py_3_12), not(Py_GIL_DISABLED)))]
 pub type PyObjectObRefcnt = Py_ssize_t;
 
+const _PyObject_MIN_ALIGNMENT: usize = 4;
+
 // PyObject_HEAD_INIT comes before the PyObject definition in object.h
 // but we put it after PyObject because HEAD_INIT uses PyObject
 
-#[repr(C)]
+// repr(align(4)) corresponds to the use of _Py_ALIGNED_DEF in object.h. It is
+// not currently possible to use constant variables with repr(align()), see
+// https://github.com/rust-lang/rust/issues/52840
+
+#[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)]
 pub struct PyObject {
     #[cfg(py_sys_config = "Py_TRACE_REFS")]
@@ -105,6 +121,8 @@ pub struct PyObject {
     pub ob_type: *mut PyTypeObject,
 }
 
+const _: () = assert!(std::mem::align_of::<PyObject>() >= _PyObject_MIN_ALIGNMENT);
+
 #[allow(
     clippy::declare_interior_mutable_const,
     reason = "contains atomic refcount on free-threaded builds"
@@ -116,7 +134,9 @@ pub const PyObject_HEAD_INIT: PyObject = PyObject {
     _ob_prev: std::ptr::null_mut(),
     #[cfg(Py_GIL_DISABLED)]
     ob_tid: 0,
-    #[cfg(all(Py_GIL_DISABLED, Py_3_14))]
+    #[cfg(all(Py_GIL_DISABLED, Py_3_15))]
+    ob_flags: refcount::_Py_STATICALLY_ALLOCATED_FLAG as u16,
+    #[cfg(all(Py_GIL_DISABLED, all(Py_3_14, not(Py_3_15))))]
     ob_flags: 0,
     #[cfg(all(Py_GIL_DISABLED, not(Py_3_14)))]
     _padding: 0,

pyo3-ffi/src/refcount.rs

@@ -14,8 +14,10 @@ use std::ptr;
 #[cfg(Py_GIL_DISABLED)]
 use std::sync::atomic::Ordering::Relaxed;
 
-#[cfg(Py_3_14)]
+#[cfg(all(Py_3_14, not(Py_3_15)))]
 const _Py_STATICALLY_ALLOCATED_FLAG: c_int = 1 << 7;
+#[cfg(Py_3_15)]
+pub(crate) const _Py_STATICALLY_ALLOCATED_FLAG: c_int = 1 << 2;
 
 #[cfg(all(Py_3_12, not(Py_3_14)))]
 const _Py_IMMORTAL_REFCNT: Py_ssize_t = {