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pythongh-105716: Fix _PyInterpreterState_IsRunningMain() For Embedders (
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pythongh-117140)

When I added _PyInterpreterState_IsRunningMain() and friends last year, I tried to accommodate applications that embed Python but don't call _PyInterpreterState_SetRunningMain() (not that they're expected to).  That mostly worked fine until my recent changes in pythongh-117049, where the subtleties with the fallback code led to failures; the change ended up breaking test_tools.test_freeze, which exercises a basic embedding situation.

The simplest fix is to drop the fallback code I originally added to _PyInterpreterState_IsRunningMain() (and later to _PyThreadState_IsRunningMain()).  I've kept the fallback in the _xxsubinterpreters module though.  I've also updated Py_FrozenMain() to call _PyInterpreterState_SetRunningMain().
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ericsnowcurrently authored Mar 22, 2024
1 parent c4bf58a commit b3d25df
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Showing 3 changed files with 39 additions and 22 deletions.
22 changes: 20 additions & 2 deletions Modules/_xxsubinterpretersmodule.c
Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,24 @@ _get_current_module(void)
}


static int
is_running_main(PyInterpreterState *interp)
{
if (_PyInterpreterState_IsRunningMain(interp)) {
return 1;
}
// Unlike with the general C-API, we can be confident that someone
// using this module for the main interpreter is doing so through
// the main program. Thus we can make this extra check. This benefits
// applications that embed Python but haven't been updated yet
// to call_PyInterpreterState_SetRunningMain().
if (_Py_IsMainInterpreter(interp)) {
return 1;
}
return 0;
}


/* Cross-interpreter Buffer Views *******************************************/

// XXX Release when the original interpreter is destroyed.
Expand Down Expand Up @@ -509,7 +527,7 @@ interp_destroy(PyObject *self, PyObject *args, PyObject *kwds)
// Ensure the interpreter isn't running.
/* XXX We *could* support destroying a running interpreter but
aren't going to worry about it for now. */
if (_PyInterpreterState_IsRunningMain(interp)) {
if (is_running_main(interp)) {
PyErr_Format(PyExc_RuntimeError, "interpreter running");
return NULL;
}
Expand Down Expand Up @@ -977,7 +995,7 @@ interp_is_running(PyObject *self, PyObject *args, PyObject *kwds)
if (interp == NULL) {
return NULL;
}
if (_PyInterpreterState_IsRunningMain(interp)) {
if (is_running_main(interp)) {
Py_RETURN_TRUE;
}
Py_RETURN_FALSE;
Expand Down
9 changes: 9 additions & 0 deletions Python/frozenmain.c
Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,12 @@ Py_FrozenMain(int argc, char **argv)
Py_ExitStatusException(status);
}

PyInterpreterState *interp = PyInterpreterState_Get();
if (_PyInterpreterState_SetRunningMain(interp) < 0) {
PyErr_Print();
exit(1);
}

#ifdef MS_WINDOWS
PyWinFreeze_ExeInit();
#endif
Expand Down Expand Up @@ -83,6 +89,9 @@ Py_FrozenMain(int argc, char **argv)
#ifdef MS_WINDOWS
PyWinFreeze_ExeTerm();
#endif

_PyInterpreterState_SetNotRunningMain(interp);

if (Py_FinalizeEx() < 0) {
sts = 120;
}
Expand Down
30 changes: 10 additions & 20 deletions Python/pystate.c
Original file line number Diff line number Diff line change
Expand Up @@ -1042,34 +1042,24 @@ _PyInterpreterState_IsRunningMain(PyInterpreterState *interp)
if (interp->threads.main != NULL) {
return 1;
}
// For now, we assume the main interpreter is always running.
if (_Py_IsMainInterpreter(interp)) {
return 1;
}
// Embedders might not know to call _PyInterpreterState_SetRunningMain(),
// so their main thread wouldn't show it is running the main interpreter's
// program. (Py_Main() doesn't have this problem.) For now this isn't
// critical. If it were, we would need to infer "running main" from other
// information, like if it's the main interpreter. We used to do that
// but the naive approach led to some inconsistencies that caused problems.
return 0;
}

#ifndef NDEBUG
static int
is_running_main(PyThreadState *tstate)
{
if (tstate->interp->threads.main != NULL) {
return tstate == tstate->interp->threads.main;
}
return 0;
}
#endif

int
_PyThreadState_IsRunningMain(PyThreadState *tstate)
{
PyInterpreterState *interp = tstate->interp;
if (interp->threads.main != NULL) {
return tstate == interp->threads.main;
}
if (_Py_IsMainInterpreter(interp)) {
return tstate->thread_id == interp->runtime->main_thread;
}
// See the note in _PyInterpreterState_IsRunningMain() about
// possible false negatives here for embedders.
return 0;
}

Expand Down Expand Up @@ -1571,7 +1561,7 @@ PyThreadState_Clear(PyThreadState *tstate)
{
assert(tstate->_status.initialized && !tstate->_status.cleared);
assert(current_fast_get()->interp == tstate->interp);
assert(!is_running_main(tstate));
assert(!_PyThreadState_IsRunningMain(tstate));
// XXX assert(!tstate->_status.bound || tstate->_status.unbound);
tstate->_status.finalizing = 1; // just in case

Expand Down Expand Up @@ -1670,7 +1660,7 @@ tstate_delete_common(PyThreadState *tstate)
assert(tstate->_status.cleared && !tstate->_status.finalized);
assert(tstate->state != _Py_THREAD_ATTACHED);
tstate_verify_not_active(tstate);
assert(!is_running_main(tstate));
assert(!_PyThreadState_IsRunningMain(tstate));

PyInterpreterState *interp = tstate->interp;
if (interp == NULL) {
Expand Down

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