[Python-checkins] GH-104668: Don't call PyOS_* hooks in subinterpreters (GH-104674)
brandtbucher
webhook-mailer at python.org
Mon May 22 15:34:42 EDT 2023
https://github.com/python/cpython/commit/357bed0bcd3c5d7c4a8caad451754a9a172aca3e
commit: 357bed0bcd3c5d7c4a8caad451754a9a172aca3e
branch: main
author: Brandt Bucher <brandtbucher at microsoft.com>
committer: brandtbucher <brandtbucher at gmail.com>
date: 2023-05-22T19:34:34Z
summary:
GH-104668: Don't call PyOS_* hooks in subinterpreters (GH-104674)
files:
A Misc/NEWS.d/next/C API/2023-05-19-10-22-34.gh-issue-104668.MLX1g9.rst
M Doc/c-api/veryhigh.rst
M Doc/whatsnew/3.12.rst
M Parser/myreadline.c
diff --git a/Doc/c-api/veryhigh.rst b/Doc/c-api/veryhigh.rst
index 513856d8a48d..000a2d3d8790 100644
--- a/Doc/c-api/veryhigh.rst
+++ b/Doc/c-api/veryhigh.rst
@@ -167,6 +167,10 @@ the same library that the Python runtime is using.
event loops, as done in the :file:`Modules/_tkinter.c` in the
Python source code.
+ .. versionchanged:: 3.12
+ This function is only called from the
+ :ref:`main interpreter <sub-interpreter-support>`.
+
.. c:var:: char* (*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, const char *)
@@ -187,6 +191,10 @@ the same library that the Python runtime is using.
:c:func:`PyMem_RawRealloc`, instead of being allocated by
:c:func:`PyMem_Malloc` or :c:func:`PyMem_Realloc`.
+ .. versionchanged:: 3.12
+ This function is only called from the
+ :ref:`main interpreter <sub-interpreter-support>`.
+
.. c:function:: PyObject* PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
This is a simplified interface to :c:func:`PyRun_StringFlags` below, leaving
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index efbd2ca3de12..4ff90664bb79 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -1476,6 +1476,15 @@ Porting to Python 3.12
Note that :c:func:`PyType_FromMetaclass` (added in Python 3.12)
already disallows creating classes whose metaclass overrides ``tp_new``.
+* :c:var:`PyOS_InputHook` and :c:var:`PyOS_ReadlineFunctionPointer` are no
+ longer called in :ref:`subinterpreters <sub-interpreter-support>`. This is
+ because clients generally rely on process-wide global state (since these
+ callbacks have no way of recovering extension module state).
+
+ This also avoids situations where extensions may find themselves running in a
+ subinterpreter that they don't support (or haven't yet been loaded in). See
+ :gh:`104668` for more info.
+
Deprecated
----------
diff --git a/Misc/NEWS.d/next/C API/2023-05-19-10-22-34.gh-issue-104668.MLX1g9.rst b/Misc/NEWS.d/next/C API/2023-05-19-10-22-34.gh-issue-104668.MLX1g9.rst
new file mode 100644
index 000000000000..7b882afd7f81
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2023-05-19-10-22-34.gh-issue-104668.MLX1g9.rst
@@ -0,0 +1,5 @@
+Don't call :c:var:`PyOS_InputHook` or :c:var:`PyOS_ReadlineFunctionPointer`
+in subinterpreters, since it's generally difficult to avoid using global
+state in their registered callbacks. This also avoids situations where
+extensions may find themselves running in a subinterpreter they don't
+support (or haven't yet been loaded in).
diff --git a/Parser/myreadline.c b/Parser/myreadline.c
index 3f0e29f051a4..7074aba74b72 100644
--- a/Parser/myreadline.c
+++ b/Parser/myreadline.c
@@ -45,7 +45,10 @@ my_fgets(PyThreadState* tstate, char *buf, int len, FILE *fp)
#endif
while (1) {
- if (PyOS_InputHook != NULL) {
+ if (PyOS_InputHook != NULL &&
+ // GH-104668: See PyOS_ReadlineFunctionPointer's comment below...
+ _Py_IsMainInterpreter(tstate->interp))
+ {
(void)(PyOS_InputHook)();
}
@@ -131,7 +134,10 @@ _PyOS_WindowsConsoleReadline(PyThreadState *tstate, HANDLE hStdIn)
wbuf = wbuf_local;
wbuflen = sizeof(wbuf_local) / sizeof(wbuf_local[0]) - 1;
while (1) {
- if (PyOS_InputHook != NULL) {
+ if (PyOS_InputHook != NULL &&
+ // GH-104668: See PyOS_ReadlineFunctionPointer's comment below...
+ _Py_IsMainInterpreter(tstate->interp))
+ {
(void)(PyOS_InputHook)();
}
if (!ReadConsoleW(hStdIn, &wbuf[total_read], wbuflen - total_read, &n_read, NULL)) {
@@ -389,11 +395,23 @@ PyOS_Readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
* a tty. This can happen, for example if python is run like
* this: python -i < test1.py
*/
- if (!isatty (fileno (sys_stdin)) || !isatty (fileno (sys_stdout)))
- rv = PyOS_StdioReadline (sys_stdin, sys_stdout, prompt);
- else
- rv = (*PyOS_ReadlineFunctionPointer)(sys_stdin, sys_stdout,
- prompt);
+ if (!isatty(fileno(sys_stdin)) || !isatty(fileno(sys_stdout)) ||
+ // GH-104668: Don't call global callbacks like PyOS_InputHook or
+ // PyOS_ReadlineFunctionPointer from subinterpreters, since it seems
+ // like there's no good way for users (like readline and tkinter) to
+ // avoid using global state to manage them. Plus, we generally don't
+ // want to cause trouble for libraries that don't know/care about
+ // subinterpreter support. If libraries really need better APIs that
+ // work per-interpreter and have ways to access module state, we can
+ // certainly add them later (but for now we'll cross our fingers and
+ // hope that nobody actually cares):
+ !_Py_IsMainInterpreter(tstate->interp))
+ {
+ rv = PyOS_StdioReadline(sys_stdin, sys_stdout, prompt);
+ }
+ else {
+ rv = (*PyOS_ReadlineFunctionPointer)(sys_stdin, sys_stdout, prompt);
+ }
Py_END_ALLOW_THREADS
PyThread_release_lock(_PyOS_ReadlineLock);
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