gh-76785: Handle Legacy Interpreters Properly (gh-117490)

This is similar to the situation with threading._DummyThread.  The methods (incl. __del__()) of interpreters.Interpreter objects must be careful with interpreters not created by interpreters.create().  The simplest thing to start with is to disable any method that modifies or runs in the interpreter.  As part of this, the runtime keeps track of where an interpreter was created.  We also handle interpreter "refcounts" properly.

2 files changed, 30 insertions, 14 deletions

diff --git a/Python/crossinterp.c b/Python/crossinterp.c
index fb0dae0..367e29d 100644
--- a/Python/crossinterp.c
+++ b/Python/crossinterp.c
@@ -1822,7 +1822,7 @@ _PyXI_FiniTypes(PyInterpreterState *interp)
 /*************/
 
 PyInterpreterState *
-_PyXI_NewInterpreter(PyInterpreterConfig *config,
+_PyXI_NewInterpreter(PyInterpreterConfig *config, long *maybe_whence,
                      PyThreadState **p_tstate, PyThreadState **p_save_tstate)
 {
     PyThreadState *save_tstate = PyThreadState_Swap(NULL);
@@ -1845,7 +1845,11 @@ _PyXI_NewInterpreter(PyInterpreterConfig *config,
     assert(tstate != NULL);
     PyInterpreterState *interp = PyThreadState_GetInterpreter(tstate);
 
-    _PyInterpreterState_SetWhence(interp, _PyInterpreterState_WHENCE_XI);
+    long whence = _PyInterpreterState_WHENCE_XI;
+    if (maybe_whence != NULL) {
+        whence = *maybe_whence;
+    }
+    _PyInterpreterState_SetWhence(interp, whence);
 
     if (p_tstate != NULL) {
         // We leave the new thread state as the current one.
@@ -1868,6 +1872,22 @@ void
 _PyXI_EndInterpreter(PyInterpreterState *interp,
                      PyThreadState *tstate, PyThreadState **p_save_tstate)
 {
+#ifndef NDEBUG
+    long whence = _PyInterpreterState_GetWhence(interp);
+#endif
+    assert(whence != _PyInterpreterState_WHENCE_RUNTIME);
+
+    if (!_PyInterpreterState_IsReady(interp)) {
+        assert(whence == _PyInterpreterState_WHENCE_UNKNOWN);
+        // PyInterpreterState_Clear() requires the GIL,
+        // which a not-ready does not have, so we don't clear it.
+        // That means there may be leaks here until clearing the
+        // interpreter is fixed.
+        PyInterpreterState_Delete(interp);
+        return;
+    }
+    assert(whence != _PyInterpreterState_WHENCE_UNKNOWN);
+
     PyThreadState *save_tstate = NULL;
     PyThreadState *cur_tstate = PyThreadState_GET();
     if (tstate == NULL) {
@@ -1889,18 +1909,7 @@ _PyXI_EndInterpreter(PyInterpreterState *interp,
         }
     }
 
-    long whence = _PyInterpreterState_GetWhence(interp);
-    assert(whence != _PyInterpreterState_WHENCE_RUNTIME);
-    if (whence == _PyInterpreterState_WHENCE_UNKNOWN) {
-        assert(!interp->_ready);
-        PyThreadState *tstate = PyThreadState_New(interp);
-        save_tstate = PyThreadState_Swap(tstate);
-        _PyInterpreterState_Clear(tstate);
-        PyInterpreterState_Delete(interp);
-    }
-    else {
-        Py_EndInterpreter(tstate);
-    }
+    Py_EndInterpreter(tstate);
 
     if (p_save_tstate != NULL) {
         save_tstate = *p_save_tstate;
diff --git a/Python/pystate.c b/Python/pystate.c
index b0fb210..acec905 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1111,6 +1111,13 @@ _PyInterpreterState_ReinitRunningMain(PyThreadState *tstate)
 // accessors
 //----------
 
+int
+_PyInterpreterState_IsReady(PyInterpreterState *interp)
+{
+    return interp->_ready;
+}
+
+
 static inline int
 check_interpreter_whence(long whence)
 {