From d12d0e7c0fe2b49c40ac4d66365147c619d6c475 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 7 Nov 2019 12:42:07 +0100
Subject: [PATCH] bpo-38733: PyErr_Occurred() caller must hold the GIL
 (GH-17080)

bpo-3605, bpo-38733: Optimize _PyErr_Occurred(): remove "tstate ==
NULL" test.

Py_FatalError() no longer calls PyErr_Occurred() if called without
holding the GIL. So PyErr_Occurred() no longer has to support
tstate==NULL case.

_Py_CheckFunctionResult(): use directly _PyErr_Occurred() to avoid
explicit "!= NULL" test.
---
 Doc/c-api/exceptions.rst           | 2 ++
 Include/internal/pycore_pyerrors.h | 3 ++-
 Objects/call.c                     | 6 ++----
 Objects/obmalloc.c                 | 5 +++--
 Python/errors.c                    | 3 +++
 5 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index a042c6eee0a..cd6df00aeb5 100644
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -374,6 +374,8 @@ Querying the error indicator
    own a reference to the return value, so you do not need to :c:func:`Py_DECREF`
    it.
 
+   The caller must hold the GIL.
+
    .. note::
 
       Do not compare the return value to a specific exception; use
diff --git a/Include/internal/pycore_pyerrors.h b/Include/internal/pycore_pyerrors.h
index edbfdfa597e..f3aa3e8b98a 100644
--- a/Include/internal/pycore_pyerrors.h
+++ b/Include/internal/pycore_pyerrors.h
@@ -10,7 +10,8 @@ extern "C" {
 
 static inline PyObject* _PyErr_Occurred(PyThreadState *tstate)
 {
-    return tstate == NULL ? NULL : tstate->curexc_type;
+    assert(tstate != NULL);
+    return tstate->curexc_type;
 }
 
 
diff --git a/Objects/call.c b/Objects/call.c
index 0d5c41295c2..a1d0b332cef 100644
--- a/Objects/call.c
+++ b/Objects/call.c
@@ -30,12 +30,10 @@ PyObject*
 _Py_CheckFunctionResult(PyThreadState *tstate, PyObject *callable,
                         PyObject *result, const char *where)
 {
-    int err_occurred = (_PyErr_Occurred(tstate) != NULL);
-
     assert((callable != NULL) ^ (where != NULL));
 
     if (result == NULL) {
-        if (!err_occurred) {
+        if (!_PyErr_Occurred(tstate)) {
             if (callable)
                 _PyErr_Format(tstate, PyExc_SystemError,
                               "%R returned NULL without setting an error",
@@ -52,7 +50,7 @@ _Py_CheckFunctionResult(PyThreadState *tstate, PyObject *callable,
         }
     }
     else {
-        if (err_occurred) {
+        if (_PyErr_Occurred(tstate)) {
             Py_DECREF(result);
 
             if (callable) {
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 50701dbd384..722e91e3db4 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -2313,12 +2313,13 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
     return data;
 }
 
-static void
+static inline void
 _PyMem_DebugCheckGIL(void)
 {
-    if (!PyGILState_Check())
+    if (!PyGILState_Check()) {
         Py_FatalError("Python memory allocator called "
                       "without holding the GIL");
+    }
 }
 
 static void *
diff --git a/Python/errors.c b/Python/errors.c
index 9658afeb9f7..1783084c336 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -218,6 +218,9 @@ PyErr_SetString(PyObject *exception, const char *string)
 PyObject* _Py_HOT_FUNCTION
 PyErr_Occurred(void)
 {
+    /* The caller must hold the GIL. */
+    assert(PyGILState_Check());
+
     PyThreadState *tstate = _PyThreadState_GET();
     return _PyErr_Occurred(tstate);
 }