gh-111375: Use NULL rather than None in the exception stack to indicate that an exception was handled (#113302)

pR0Ps · web-flow · commit a2dd0e7038ad · 2023-12-21T01:46:41.000Z
diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-12-19-22-03-43.gh-issue-111375.M9vuA6.rst b/Misc/NEWS.d/next/Core and Builtins/2023-12-19-22-03-43.gh-issue-111375.M9vuA6.rst
@@ -0,0 +1,2 @@
+Only use ``NULL`` in the exception stack to indicate an exception was
+handled. Patch by Carey Metcalfe.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
@@ -811,7 +811,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno, void *Py_UNUSED(ignore
             PyObject *exc = _PyFrame_StackPop(f->f_frame);
             assert(PyExceptionInstance_Check(exc) || exc == Py_None);
             PyThreadState *tstate = _PyThreadState_GET();
-            Py_XSETREF(tstate->exc_info->exc_value, exc);
+            Py_XSETREF(tstate->exc_info->exc_value, exc == Py_None ? NULL : exc);
         }
         else {
             PyObject *v = _PyFrame_StackPop(f->f_frame);
diff --git a/Python/bytecodes.c b/Python/bytecodes.c
@@ -1100,7 +1100,7 @@ dummy_func(
 
         inst(POP_EXCEPT, (exc_value -- )) {
             _PyErr_StackItem *exc_info = tstate->exc_info;
-            Py_XSETREF(exc_info->exc_value, exc_value);
+            Py_XSETREF(exc_info->exc_value, exc_value == Py_None ? NULL : exc_value);
         }
 
         inst(RERAISE, (values[oparg], exc -- values[oparg])) {
diff --git a/Python/errors.c b/Python/errors.c
@@ -121,11 +121,11 @@ _PyErr_GetTopmostException(PyThreadState *tstate)
     _PyErr_StackItem *exc_info = tstate->exc_info;
     assert(exc_info);
 
-    while ((exc_info->exc_value == NULL || exc_info->exc_value == Py_None) &&
-           exc_info->previous_item != NULL)
+    while (exc_info->exc_value == NULL && exc_info->previous_item != NULL)
     {
         exc_info = exc_info->previous_item;
     }
+    assert(!Py_IsNone(exc_info->exc_value));
     return exc_info;
 }
 
@@ -592,7 +592,7 @@ PyErr_GetHandledException(void)
 void
 _PyErr_SetHandledException(PyThreadState *tstate, PyObject *exc)
 {
-    Py_XSETREF(tstate->exc_info->exc_value, Py_XNewRef(exc));
+    Py_XSETREF(tstate->exc_info->exc_value, Py_XNewRef(exc == Py_None ? NULL : exc));
 }
 
 void
diff --git a/Python/executor_cases.c.h b/Python/executor_cases.c.h
diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Only use ``NULL`` in the exception stack to indicate an exception was
	`2`	`+handled. Patch by Carey Metcalfe.`
Original file line number	Diff line number	Diff line change
`@@ -811,7 +811,7 @@ frame_setlineno(PyFrameObject f, PyObject p_new_lineno, void *Py_UNUSED(ignore`
`811`	`811`	`PyObject *exc = _PyFrame_StackPop(f->f_frame);`
`812`	`812`	`assert(PyExceptionInstance_Check(exc) \|\| exc == Py_None);`
`813`	`813`	`PyThreadState *tstate = _PyThreadState_GET();`
`814`		`- Py_XSETREF(tstate->exc_info->exc_value, exc);`
	`814`	`+ Py_XSETREF(tstate->exc_info->exc_value, exc == Py_None ? NULL : exc);`
`815`	`815`	`}`
`816`	`816`	`else {`
`817`	`817`	`PyObject *v = _PyFrame_StackPop(f->f_frame);`
Original file line number	Diff line number	Diff line change
`@@ -1100,7 +1100,7 @@ dummy_func(`
`1100`	`1100`
`1101`	`1101`	`inst(POP_EXCEPT, (exc_value -- )) {`
`1102`	`1102`	`_PyErr_StackItem *exc_info = tstate->exc_info;`
`1103`		`- Py_XSETREF(exc_info->exc_value, exc_value);`
	`1103`	`+ Py_XSETREF(exc_info->exc_value, exc_value == Py_None ? NULL : exc_value);`
`1104`	`1104`	`}`
`1105`	`1105`
`1106`	`1106`	`inst(RERAISE, (values[oparg], exc -- values[oparg])) {`
Original file line number	Diff line number	Diff line change
`@@ -121,11 +121,11 @@ _PyErr_GetTopmostException(PyThreadState *tstate)`
`121`	`121`	`_PyErr_StackItem *exc_info = tstate->exc_info;`
`122`	`122`	`assert(exc_info);`
`123`	`123`
`124`		`- while ((exc_info->exc_value == NULL \|\| exc_info->exc_value == Py_None) &&`
`125`		`- exc_info->previous_item != NULL)`
	`124`	`+ while (exc_info->exc_value == NULL && exc_info->previous_item != NULL)`
`126`	`125`	`{`
`127`	`126`	`exc_info = exc_info->previous_item;`
`128`	`127`	`}`
	`128`	`+ assert(!Py_IsNone(exc_info->exc_value));`
`129`	`129`	`return exc_info;`
`130`	`130`	`}`
`131`	`131`
`@@ -592,7 +592,7 @@ PyErr_GetHandledException(void)`
`592`	`592`	`void`
`593`	`593`	`_PyErr_SetHandledException(PyThreadState tstate, PyObject exc)`
`594`	`594`	`{`
`595`		`- Py_XSETREF(tstate->exc_info->exc_value, Py_XNewRef(exc));`
	`595`	`+ Py_XSETREF(tstate->exc_info->exc_value, Py_XNewRef(exc == Py_None ? NULL : exc));`
`596`	`596`	`}`
`597`	`597`
`598`	`598`	`void`