bpo-45711: Change exc_info related APIs to derive type and traceback from the exception instance (GH-29780)

1 files changed, 48 insertions, 26 deletions

diff --git a/Python/errors.c b/Python/errors.c
index 6e74d19..0a8b5a2 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -470,6 +470,33 @@ PyErr_Clear(void)
     _PyErr_Clear(tstate);
 }
 
+static PyObject*
+get_exc_type(PyObject *exc_value)  /* returns a borrowed ref */
+{
+    if (exc_value == NULL || exc_value == Py_None) {
+        return Py_None;
+    }
+    else {
+        assert(PyExceptionInstance_Check(exc_value));
+        PyObject *type = PyExceptionInstance_Class(exc_value);
+        assert(type != NULL);
+        return type;
+    }
+}
+
+static PyObject*
+get_exc_traceback(PyObject *exc_value)  /* returns a borrowed ref */
+{
+    if (exc_value == NULL || exc_value == Py_None) {
+        return Py_None;
+    }
+    else {
+        assert(PyExceptionInstance_Check(exc_value));
+        PyObject *tb = PyException_GetTraceback(exc_value);
+        Py_XDECREF(tb);
+        return tb ? tb : Py_None;
+    }
+}
 
 void
 _PyErr_GetExcInfo(PyThreadState *tstate,
@@ -477,18 +504,9 @@ _PyErr_GetExcInfo(PyThreadState *tstate,
 {
     _PyErr_StackItem *exc_info = _PyErr_GetTopmostException(tstate);
 
+    *p_type = get_exc_type(exc_info->exc_value);
     *p_value = exc_info->exc_value;
-    *p_traceback = exc_info->exc_traceback;
-
-    if (*p_value == NULL || *p_value == Py_None) {
-        assert(exc_info->exc_type == NULL || exc_info->exc_type == Py_None);
-        *p_type = Py_None;
-    }
-    else {
-        assert(PyExceptionInstance_Check(*p_value));
-        assert(exc_info->exc_type == PyExceptionInstance_Class(*p_value));
-        *p_type = PyExceptionInstance_Class(*p_value);
-    }
+    *p_traceback = get_exc_traceback(exc_info->exc_value);
 
     Py_XINCREF(*p_type);
     Py_XINCREF(*p_value);
@@ -504,7 +522,7 @@ PyErr_GetExcInfo(PyObject **p_type, PyObject **p_value, PyObject **p_traceback)
 }
 
 void
-PyErr_SetExcInfo(PyObject *p_type, PyObject *p_value, PyObject *p_traceback)
+PyErr_SetExcInfo(PyObject *type, PyObject *value, PyObject *traceback)
 {
     PyObject *oldtype, *oldvalue, *oldtraceback;
     PyThreadState *tstate = _PyThreadState_GET();
@@ -513,9 +531,16 @@ PyErr_SetExcInfo(PyObject *p_type, PyObject *p_value, PyObject *p_traceback)
     oldvalue = tstate->exc_info->exc_value;
     oldtraceback = tstate->exc_info->exc_traceback;
 
-    tstate->exc_info->exc_type = p_type;
-    tstate->exc_info->exc_value = p_value;
-    tstate->exc_info->exc_traceback = p_traceback;
+
+    tstate->exc_info->exc_type = get_exc_type(value);
+    Py_XINCREF(tstate->exc_info->exc_type);
+    tstate->exc_info->exc_value = value;
+    tstate->exc_info->exc_traceback = get_exc_traceback(value);
+    Py_XINCREF(tstate->exc_info->exc_traceback);
+
+    /* These args are no longer used, but we still need to steal a ref */
+    Py_XDECREF(type);
+    Py_XDECREF(traceback);
 
     Py_XDECREF(oldtype);
     Py_XDECREF(oldvalue);
@@ -527,22 +552,19 @@ PyObject*
 _PyErr_StackItemToExcInfoTuple(_PyErr_StackItem *err_info)
 {
     PyObject *exc_value = err_info->exc_value;
-    if (exc_value == NULL) {
-        exc_value = Py_None;
-    }
 
-    assert(exc_value == Py_None || PyExceptionInstance_Check(exc_value));
+    assert(exc_value == NULL ||
+           exc_value == Py_None ||
+           PyExceptionInstance_Check(exc_value));
 
-    PyObject *exc_type = PyExceptionInstance_Check(exc_value) ?
-               PyExceptionInstance_Class(exc_value) :
-               Py_None;
+    PyObject *exc_type = get_exc_type(exc_value);
+    PyObject *exc_traceback = get_exc_traceback(exc_value);
 
     return Py_BuildValue(
         "(OOO)",
-        exc_type,
-        exc_value,
-        err_info->exc_traceback != NULL ?
-            err_info->exc_traceback : Py_None);
+        exc_type ? exc_type : Py_None,
+        exc_value ? exc_value : Py_None,
+        exc_traceback ? exc_traceback : Py_None);
 }