Add _PyThreadState_UncheckedGet()

Issue #26154: Add a new private _PyThreadState_UncheckedGet() function which
gets the current thread state, but don't call Py_FatalError() if it is NULL.

Python 3.5.1 removed the _PyThreadState_Current symbol from the Python C API to
no more expose complex and private atomic types. Atomic types depends on the
compiler or can even depend on compiler options. The new function
_PyThreadState_UncheckedGet() allows to get the variable value without having
to care of the exact implementation of atomic types.

Changes:

* Replace direct usage of the _PyThreadState_Current variable with a call to
  _PyThreadState_UncheckedGet().
* In pystate.c, replace direct usage of the _PyThreadState_Current variable
  with the PyThreadState_GET() macro for readability.
* Document also PyThreadState_Get() in pystate.h

1 files changed, 1 insertions, 7 deletions

diff --git a/Python/errors.c b/Python/errors.c
index 7b67566727..5ff1e4c81a 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -152,13 +152,7 @@ PyErr_SetString(PyObject *exception, const char *string)
 PyObject *
 PyErr_Occurred(void)
 {
-    /* If there is no thread state, PyThreadState_GET calls
-       Py_FatalError, which calls PyErr_Occurred.  To avoid the
-       resulting infinite loop, we inline PyThreadState_GET here and
-       treat no thread as no error. */
-    PyThreadState *tstate =
-        ((PyThreadState*)_Py_atomic_load_relaxed(&_PyThreadState_Current));
-
+    PyThreadState *tstate = _PyThreadState_UncheckedGet();
     return tstate == NULL ? NULL : tstate->curexc_type;
 }