Issue #18408: PyEval_EvalFrameEx() and PyEval_CallObjectWithKeywords() now fail

with an assertion error if they are called with an exception set
(PyErr_Occurred()).

If these functions are called with an exception set, the exception may be
cleared and so the caller looses its exception.

Add also assertions to PyEval_CallObjectWithKeywords() and call_function() to
check if the function succeed with no exception set, or the function failed
with an exception set.

1 files changed, 11 insertions, 0 deletions

diff --git a/Python/errors.c b/Python/errors.c
index c693b78cac..b0f8b18939 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -71,6 +71,11 @@ PyErr_SetObject(PyObject *exception, PyObject *value)
         if (value == NULL || !PyExceptionInstance_Check(value)) {
             /* We must normalize the value right now */
             PyObject *args, *fixed_value;
+#ifdef Py_DEBUG
+            /* in debug mode, PyEval_EvalFrameEx() fails with an assertion
+               error if an exception is set when it is called */
+            PyErr_Clear();
+#endif
             if (value == NULL || value == Py_None)
                 args = PyTuple_New(0);
             else if (PyTuple_Check(value)) {
@@ -707,6 +712,12 @@ PyErr_Format(PyObject *exception, const char *format, ...)
     va_start(vargs);
 #endif
 
+#ifdef Py_DEBUG
+    /* in debug mode, PyEval_EvalFrameEx() fails with an assertion error
+       if an exception is set when it is called */
+    PyErr_Clear();
+#endif
+
     string = PyUnicode_FromFormatV(format, vargs);
     PyErr_SetObject(exception, string);
     Py_XDECREF(string);