Issue #18501, #18408: Fix expat handlers in pyexpat, don't call Python

functions if a Python exception was raised

Modules/pyexpat.c

@@ -402,6 +402,10 @@ static void
 my_CharacterDataHandler(void *userData, const XML_Char *data, int len)
 {
     xmlparseobject *self = (xmlparseobject *) userData;
+
+    if (PyErr_Occurred())
+        return;
+
     if (self->buffer == NULL)
         call_character_handler(self, data, len);
     else {
@@ -436,6 +440,9 @@ my_StartElementHandler(void *userData,
         PyObject *container, *rv, *args;
         int i, max;
 
+        if (PyErr_Occurred())
+            return;
+
         if (flush_character_buffer(self) < 0)
             return;
         /* Set max to the number of slots filled in atts[]; max/2 is
@@ -519,6 +526,8 @@ my_##NAME##Handler PARAMS {\
     INIT \
 \
     if (have_handler(self, NAME)) { \
+        if (PyErr_Occurred()) \
+            return RETURN; \
         if (flush_character_buffer(self) < 0) \
             return RETURN; \
         args = Py_BuildValue PARAM_FORMAT ;\
@@ -633,6 +642,9 @@ my_ElementDeclHandler(void *userData,
         PyObject *rv = NULL;
         PyObject *modelobj, *nameobj;
 
+        if (PyErr_Occurred())
+            return;
+
         if (flush_character_buffer(self) < 0)
             goto finally;
         modelobj = conv_content_model(model, (conv_string_to_unicode));
@@ -1125,6 +1137,9 @@ PyUnknownEncodingHandler(void *encodingHandlerData,
     void *data;
     unsigned int kind;
 
+    if (PyErr_Occurred())
+        return XML_STATUS_ERROR;
+
     if (template_buffer[1] == 0) {
         for (i = 0; i < 256; i++)
             template_buffer[i] = i;