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return existing module on Python 3.9 and up

This commit is contained in:
David Hewitt 2023-09-14 14:40:43 +02:00
parent 1338020511
commit f17e703167
5 changed files with 67 additions and 38 deletions
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2
guide/src/building_and_distribution.md
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@ -276,7 +276,7 @@ If you encounter these or other complications when linking the interpreter stati
### Import your module when embedding the Python interpreter
When you run your Rust binary with an embedded interpreter, any `#[pymodule]` created modules won't be accessible to import unless added to a table called `PyImport_Inittab` before the embedded interpreter is initialized. This will cause Python statements in your embedded interpreter such as `import your_new_module` to fail. You can call the macro [`append_to_inittab`]({{#PYO3_DOCS_URL}}/pyo3/macro.append_to_inittab.html) with your module before initializing the Python interpreter to add the module function into that table. (The Python interpreter will be initialized by calling `prepare_freethreaded_python`, `with_embedded_interpreter`, or `Python::with_gil` with the [`auto-initialize`](features.md#auto-initialize) feature enabled.)
When you run your Rust binary with an embedded interpreter, any `#[pymodule]` created modules won't be accessible to import unless added to a table called `PyImport_Inittab` before the embedded interpreter is initialized. This will cause Python statements in your embedded interpreter such as `import your_new_module` to fail. You can call the macro [`append_to_inittab`]({{#PYO3_DOCS_URL}}/pyo3/macro.append_to_inittab.html) with your module before initializing the Python interpreter to add the module function into that table. (The Python interpreter will be initialized by calling `prepare_freethreaded_python`, `with_embedded_python_interpreter`, or `Python::with_gil` with the [`auto-initialize`](features.md#auto-initialize) feature enabled.)
## Cross Compiling

2
newsfragments/3446.changed.md
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@ -1 +1 @@
Relax multiple import check to only prevent use of subinterpreters.
`#[pymodule]` will now return the same module object on repeated import by the same Python interpreter, on Python 3.9 and up.

5
pyo3-build-config/src/lib.rs
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@ -146,11 +146,6 @@ pub fn print_feature_cfgs() {
if rustc_minor_version >= 59 {
println!("cargo:rustc-cfg=thread_local_const_init");
}
// Enable use of OnceLock on Rust 1.70 and greater
if rustc_minor_version >= 70 {
println!("cargo:rustc-cfg=once_lock");
}
}
/// Private exports used in PyO3's build.rs

9
pytests/tests/test_misc.py
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@ -1,5 +1,6 @@
import importlib
import platform
import sys
import pyo3_pytests.misc
import pytest
@ -10,6 +11,10 @@ def test_issue_219():
pyo3_pytests.misc.issue_219()
@pytest.mark.xfail(
platform.python_implementation() == "CPython" and sys.version_info < (3, 9),
reason="Cannot identify subinterpreters on Python older than 3.9",
)
def test_multiple_imports_same_interpreter_ok():
spec = importlib.util.find_spec("pyo3_pytests.pyo3_pytests")
@ -17,6 +22,10 @@ def test_multiple_imports_same_interpreter_ok():
assert dir(module) == dir(pyo3_pytests.pyo3_pytests)
@pytest.mark.xfail(
platform.python_implementation() == "CPython" and sys.version_info < (3, 9),
reason="Cannot identify subinterpreters on Python older than 3.9",
)
@pytest.mark.skipif(
platform.python_implementation() == "PyPy",
reason="PyPy does not support subinterpreters",

87
src/impl_/pymodule.rs
View File

@ -1,23 +1,24 @@
//! Implementation details of `#[pymodule]` which need to be accessible from proc-macro generated code.
use std::cell::UnsafeCell;
#[cfg(once_lock)]
use std::sync::OnceLock;
#[cfg(not(once_lock))]
use parking_lot::Mutex;
#[cfg(all(not(PyPy), Py_3_9))]
use std::sync::atomic::{AtomicI64, Ordering};
use crate::{exceptions::PyImportError, ffi, types::PyModule, Py, PyResult, Python};
#[cfg(not(PyPy))]
use crate::exceptions::PyImportError;
use crate::{ffi, sync::GILOnceCell, types::PyModule, Py, PyResult, Python};
/// `Sync` wrapper of `ffi::PyModuleDef`.
pub struct ModuleDef {
// wrapped in UnsafeCell so that Rust compiler treats this as interior mutability
ffi_def: UnsafeCell<ffi::PyModuleDef>,
initializer: ModuleInitializer,
#[cfg(once_lock)]
interpreter: OnceLock<i64>,
#[cfg(not(once_lock))]
interpreter: Mutex<Option<i64>>,
/// Interpreter ID where module was initialized (not applicable on PyPy).
#[cfg(all(not(PyPy), Py_3_9))]
interpreter: AtomicI64,
/// Initialized module object, cached to avoid reinitialization.
module: GILOnceCell<Py<PyModule>>,
}
/// Wrapper to enable initializer to be used in const fns.
@ -56,10 +57,10 @@ impl ModuleDef {
ModuleDef {
ffi_def,
initializer,
#[cfg(once_lock)]
interpreter: OnceLock::new(),
#[cfg(not(once_lock))]
interpreter: Mutex::new(None),
// -1 is never expected to be a valid interpreter ID
#[cfg(all(not(PyPy), Py_3_9))]
interpreter: AtomicI64::new(-1),
module: GILOnceCell::new(),
}
}
/// Builds a module using user given initializer. Used for [`#[pymodule]`][crate::pymodule].
@ -79,29 +80,53 @@ impl ModuleDef {
))?;
}
}
let module = unsafe {
Py::<PyModule>::from_owned_ptr_or_err(py, ffi::PyModule_Create(self.ffi_def.get()))?
};
let current_interpreter =
unsafe { ffi::PyInterpreterState_GetID(ffi::PyInterpreterState_Get()) };
let initialized_interpreter = py.allow_threads(|| {
#[cfg(once_lock)]
// Check the interpreter ID has not changed, since we currently have no way to guarantee
// that static data is not reused across interpreters.
//
// PyPy does not have subinterpreters, so no need to check interpreter ID.
#[cfg(not(PyPy))]
{
#[cfg(Py_3_9)]
{
*self.interpreter.get_or_init(|| current_interpreter)
let current_interpreter =
unsafe { ffi::PyInterpreterState_GetID(ffi::PyInterpreterState_Get()) };
crate::err::error_on_minusone(py, current_interpreter)?;
if let Err(initialized_interpreter) = self.interpreter.compare_exchange(
-1,
current_interpreter,
Ordering::SeqCst,
Ordering::SeqCst,
) {
if initialized_interpreter != current_interpreter {
return Err(PyImportError::new_err(
"PyO3 modules do not yet support subinterpreters, see https://github.com/PyO3/pyo3/issues/576",
));
}
}
}
#[cfg(not(once_lock))]
#[cfg(not(Py_3_9))]
{
*self.interpreter.lock().get_or_insert(current_interpreter)
// CPython before 3.9 does not have APIs to check the interpreter ID, so best that can be
// done to guard against subinterpreters is fail if the module is initialized twice
if self.module.get(py).is_some() {
return Err(PyImportError::new_err(
"PyO3 modules compiled for CPython 3.8 or older may only be initialized once per interpreter process"
));
}
}
});
if current_interpreter != initialized_interpreter {
return Err(PyImportError::new_err(
"PyO3 modules do not yet support subinterpreters, see https://github.com/PyO3/pyo3/issues/576",
));
}
(self.initializer.0)(py, module.as_ref(py))?;
Ok(module)
self.module
.get_or_try_init(py, || {
let module = unsafe {
Py::<PyModule>::from_owned_ptr_or_err(
py,
ffi::PyModule_Create(self.ffi_def.get()),
)?
};
(self.initializer.0)(py, module.as_ref(py))?;
Ok(module)
})
.map(|py_module| py_module.clone_ref(py))
}
}