Do not backport the API/ABI changes.

Author: ericsnowcurrently

Include/internal/pycore_pystate.h

@@ -84,7 +84,7 @@ PyAPI_FUNC(PyObject *) _PyInterpreterState_GetIDObject(PyInterpreterState *);
 PyAPI_FUNC(int) _PyInterpreterState_SetRunningMain(PyInterpreterState *);
 PyAPI_FUNC(void) _PyInterpreterState_SetNotRunningMain(PyInterpreterState *);
 PyAPI_FUNC(int) _PyInterpreterState_IsRunningMain(PyInterpreterState *);
-PyAPI_FUNC(void) _PyErr_SetInterpreterAlreadyRunning(void);
+PyAPI_FUNC(int) _PyInterpreterState_FailIfRunningMain(PyInterpreterState *);
 
 extern int _PyThreadState_IsRunningMain(PyThreadState *);
 extern void _PyInterpreterState_ReinitRunningMain(PyThreadState *);

Python/crossinterp.c

@@ -985,7 +985,8 @@ _PyXI_ApplyErrorCode(_PyXI_errcode code, PyInterpreterState *interp)
         break;
     case _PyXI_ERR_ALREADY_RUNNING:
         assert(interp != NULL);
-        _PyErr_SetInterpreterAlreadyRunning();
+        // In 3.14+ we use _PyErr_SetInterpreterAlreadyRunning().
+        PyErr_SetString(PyExc_InterpreterError, "interpreter already running");
         break;
     case _PyXI_ERR_MAIN_NS_FAILURE:
         PyErr_SetString(PyExc_InterpreterError,

Python/pystate.c

@@ -1050,17 +1050,12 @@ get_main_thread(PyInterpreterState *interp)
     return _Py_atomic_load_ptr_relaxed(&interp->threads.main);
 }
 
-void
-_PyErr_SetInterpreterAlreadyRunning(void)
-{
-    PyErr_SetString(PyExc_InterpreterError, "interpreter already running");
-}
-
 int
 _PyInterpreterState_SetRunningMain(PyInterpreterState *interp)
 {
     if (get_main_thread(interp) != NULL) {
-        _PyErr_SetInterpreterAlreadyRunning();
+        // In 3.14+ we use _PyErr_SetInterpreterAlreadyRunning().
+        PyErr_SetString(PyExc_InterpreterError, "interpreter already running");
         return -1;
     }
     PyThreadState *tstate = current_fast_get();
@@ -1106,6 +1101,18 @@ _PyThreadState_IsRunningMain(PyThreadState *tstate)
     return get_main_thread(interp) == tstate;
 }
 
+// This has been removed in 3.14.
+int
+_PyInterpreterState_FailIfRunningMain(PyInterpreterState *interp)
+{
+    if (get_main_thread(interp) != NULL) {
+        PyErr_SetString(PyExc_InterpreterError,
+                        "interpreter already running");
+        return -1;
+    }
+    return 0;
+}
+
 void
 _PyInterpreterState_ReinitRunningMain(PyThreadState *tstate)
 {