This is strictly about moving the "obmalloc" runtime state from
`_PyRuntimeState` to `PyInterpreterState`. Doing so improves isolation
between interpreters, specifically most of the memory (incl. objects)
allocated for each interpreter's use. This is important for a
per-interpreter GIL, but such isolation is valuable even without it.
FWIW, a per-interpreter obmalloc is the proverbial
canary-in-the-coalmine when it comes to the isolation of objects between
interpreters. Any object that leaks (unintentionally) to another
interpreter is highly likely to cause a crash (on debug builds at
least). That's a useful thing to know, relative to interpreter
isolation.
The function is like Py_AtExit() but for a single interpreter. This is a companion to the atexit module's register() function, taking a C callback instead of a Python one.
We also update the _xxinterpchannels module to use _Py_AtExit(), which is the motivating case. (This is inspired by pain points felt while working on gh-101660.)
Prior to this change, errors in _Py_NewInterpreterFromConfig() were always fatal. Instead, callers should be able to handle such errors and keep going. That's what this change supports. (This was an oversight in the original implementation of _Py_NewInterpreterFromConfig().) Note that the existing [fatal] behavior of the public Py_NewInterpreter() is preserved.
https://github.com/python/cpython/issues/98608
Enforcing (optionally) the restriction set by PEP 489 makes sense. Furthermore, this sets the stage for a potential restriction related to a per-interpreter GIL.
This change includes the following:
* add tests for extension module subinterpreter compatibility
* add _PyInterpreterConfig.check_multi_interp_extensions
* add Py_RTFLAGS_MULTI_INTERP_EXTENSIONS
* add _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
* fail iff the module does not implement multi-phase init and the current interpreter is configured to check
https://github.com/python/cpython/issues/98627
* Make sure that the current exception is always normalized.
* Remove redundant type and traceback fields for the current exception.
* Add new API functions: PyErr_GetRaisedException, PyErr_SetRaisedException
* Add new API functions: PyException_GetArgs, PyException_SetArgs
Not comprehensive, best effort warning. There are cases when threads exist on some platforms that this code cannot detect. macOS when API permissions allow and Linux with a readable /proc procfs present are the currently supported cases where a warning should show up reliably.
Starting with a DeprecationWarning for now, it is less disruptive than something like RuntimeWarning and most likely to only be seen in people's CI tests - a good place to start with this messaging.
The Py_CLEAR(), Py_SETREF() and Py_XSETREF() macros now only evaluate
their arguments once. If an argument has side effects, these side
effects are no longer duplicated.
Use temporary variables to avoid duplicating side effects of macro
arguments. If available, use _Py_TYPEOF() to avoid type punning.
Otherwise, use memcpy() for the assignment to prevent a
miscompilation with strict aliasing caused by type punning.
Add _Py_TYPEOF() macro: __typeof__() on GCC and clang.
Add test_py_clear() and test_py_setref() unit tests to _testcapi.
The ``structmember.h`` header is deprecated, though it continues to be available
and there are no plans to remove it. There are no deprecation warnings. Old code
can stay unchanged (unless the extra include and non-namespaced macros bother
you greatly). Specifically, no uses in CPython are updated -- that would just be
unnecessary churn.
The ``structmember.h`` header is deprecated, though it continues to be
available and there are no plans to remove it.
Its contents are now available just by including ``Python.h``,
with a ``Py`` prefix added if it was missing:
- `PyMemberDef`, `PyMember_GetOne` and`PyMember_SetOne`
- Type macros like `Py_T_INT`, `Py_T_DOUBLE`, etc.
(previously ``T_INT``, ``T_DOUBLE``, etc.)
- The flags `Py_READONLY` (previously ``READONLY``) and
`Py_AUDIT_READ` (previously all uppercase)
Several items are not exposed from ``Python.h``:
- `T_OBJECT` (use `Py_T_OBJECT_EX`)
- `T_NONE` (previously undocumented, and pretty quirky)
- The macro ``WRITE_RESTRICTED`` which does nothing.
- The macros ``RESTRICTED`` and ``READ_RESTRICTED``, equivalents of
`Py_AUDIT_READ`.
- In some configurations, ``<stddef.h>`` is not included from ``Python.h``.
It should be included manually when using ``offsetof()``.
The deprecated header continues to provide its original
contents under the original names.
Your old code can stay unchanged, unless the extra include and non-namespaced
macros bother you greatly.
There is discussion on the issue to rename `T_PYSSIZET` to `PY_T_SSIZE` or
similar. I chose not to do that -- users will probably copy/paste that with any
spelling, and not renaming it makes migration docs simpler.
Co-Authored-By: Alexander Belopolsky <abalkin@users.noreply.github.com>
Co-Authored-By: Matthias Braun <MatzeB@users.noreply.github.com>
The Py_CLEAR(), Py_SETREF() and Py_XSETREF() macros now only evaluate
their argument once. If an argument has side effects, these side
effects are no longer duplicated.
Add test_py_clear() and test_py_setref() unit tests to _testcapi.
Add PyFrame_GetVar() and PyFrame_GetVarString() functions to get a
frame variable by its name.
Move PyFrameObject C API tests from test_capi to test_frame.
Previously, the optional restrictions on subinterpreters were: disallow fork, subprocess, and threads. By default, we were disallowing all three for "isolated" interpreters. We always allowed all three for the main interpreter and those created through the legacy `Py_NewInterpreter()` API.
Those settings were a bit conservative, so here we've adjusted the optional restrictions to: fork, exec, threads, and daemon threads. The default for "isolated" interpreters disables fork, exec, and daemon threads. Regular threads are allowed by default. We continue always allowing everything For the main interpreter and the legacy API.
In the code, we add `_PyInterpreterConfig.allow_exec` and `_PyInterpreterConfig.allow_daemon_threads`. We also add `Py_RTFLAGS_DAEMON_THREADS` and `Py_RTFLAGS_EXEC`.
(see https://github.com/python/cpython/issues/98608)
This change does the following:
1. change the argument to a new `_PyInterpreterConfig` struct
2. rename the function to `_Py_NewInterpreterFromConfig()`, inspired by `Py_InitializeFromConfig()` (takes a `_PyInterpreterConfig` instead of `isolated_subinterpreter`)
3. split up the boolean `isolated_subinterpreter` into the corresponding multiple granular settings
* allow_fork
* allow_subprocess
* allow_threads
4. add `PyInterpreterState.feature_flags` to store those settings
5. add a function for checking if a feature is enabled on an opaque `PyInterpreterState *`
6. drop `PyConfig._isolated_interpreter`
The existing default (see `Py_NewInterpeter()` and `Py_Initialize*()`) allows fork, subprocess, and threads and the optional "isolated" interpreter (see the `_xxsubinterpreters` module) disables all three. None of that changes here; the defaults are preserved.
Note that the given `_PyInterpreterConfig` will not be used outside `_Py_NewInterpreterFromConfig()`, nor preserved. This contrasts with how `PyConfig` is currently preserved, used, and even modified outside `Py_InitializeFromConfig()`. I'd rather just avoid that mess from the start for `_PyInterpreterConfig`. We can preserve it later if we find an actual need.
This change allows us to follow up with a number of improvements (e.g. stop disallowing subprocess and support disallowing exec instead).
(Note that this PR adds "private" symbols. We'll probably make them public, and add docs, in a separate change.)
Eric Snow
Brett Simmers
Artem Mukhin
Jacob Bower
Petr Viktorin
Irit Katriel
Erlend E. Aasland
Mark Shannon
Nikita Sobolev
Matthieu Dartiailh
ram vikram singh
Kumar Aditya
Gregory P. Smith
Bill Fisher
Victor Stinner
Carl Meyer
Michael Droettboom