Deal with controller failures in the init path

It is very difficult to tell in the chain from
as_async through the other thread, the tp_new
call and all the intermediate CPython APIs
when failure occurred and who cleans up the
mess.  This finally gets everything right
by making the boxed_call doing the init free
the connection unless tp_new succeeds.

Author: rogerbinns

src/async.c

@@ -31,6 +31,7 @@ typedef struct BoxedCall
       PyObject *connection;
       PyObject *args;
       PyObject *kwargs;
+      int call_success;
     } ConnectionInit;
 
     /* note this must be the largest member of the union because
@@ -81,6 +82,13 @@ BoxedCall_clear(PyObject *self_)
     Py_DECREF(self->ConnectionInit.connection);
     Py_DECREF(self->ConnectionInit.args);
     Py_XDECREF(self->ConnectionInit.kwargs);
+    if (!self->ConnectionInit.call_success)
+    {
+      /* this causes close on init failure so threads don't get leaked
+         because our original code in as_async can't know about
+         downstream failures  */
+      Py_DECREF(self->ConnectionInit.connection);
+    }
     break;
 
   case FastCallWithKeywords: {
@@ -135,8 +143,11 @@ BoxedCall_internal_call(BoxedCall *self)
       if (0
           == Py_TYPE(self->ConnectionInit.connection)
                  ->tp_init(self->ConnectionInit.connection, self->ConnectionInit.args, self->ConnectionInit.kwargs))
+      {
         result = Py_NewRef(self->ConnectionInit.connection);
-      break;
+        self->ConnectionInit.call_success = 1;
+      }
+        break;
     case FastCallWithKeywords:
       result = self->FastCallWithKeywords.function(
           self->FastCallWithKeywords.object, self->FastCallWithKeywords.fast_args + 1,
@@ -165,10 +176,6 @@ BoxedCall_internal_call(BoxedCall *self)
   if (!result && PyErr_Occurred() && !PyErr_ExceptionMatches(PyExc_StopAsyncIteration)
       && !PyErr_ExceptionMatches(PyExc_StopIteration))
   {
-    if (self->call_type == ConnectionInit)
-      /* this causes close on init failure so threads don't get leaked */
-      Py_DECREF(self->ConnectionInit.connection);
-
     AddTraceBackHere(__FILE__, __LINE__, "apsw.aio.BoxedCall.__call__", "{s:i}", "call_type", (int)self->call_type);
   }
 

src/connection.c

@@ -808,6 +808,7 @@ Connection_as_async(PyObject *klass_, PyObject *args, PyObject *kwargs)
   boxed_call->ConnectionInit.connection = Py_NewRef((PyObject *)connection);
   boxed_call->ConnectionInit.args = Py_NewRef(args);
   boxed_call->ConnectionInit.kwargs = Py_XNewRef(kwargs);
+  boxed_call->ConnectionInit.call_success = 0;
   connection->async_controller = NULL;
 
   if(!PyContextVar_Get(async_controller_context_var, NULL, &connection->async_controller))
@@ -827,17 +828,15 @@ Connection_as_async(PyObject *klass_, PyObject *args, PyObject *kwargs)
   if (!connection->async_controller)
     goto error;
 
-  PyObject *result = async_send_boxed_call((PyObject *)connection, (PyObject*)boxed_call);
+  PyObject *result = async_send_boxed_call((PyObject *)connection, (PyObject *)boxed_call);
   /* send_boxed took the reference */
   boxed_call = NULL;
-  connection = NULL;
 
   if (result)
     return result;
 
 error:
   assert(PyErr_Occurred());
-  Py_XDECREF((PyObject *)connection);
   Py_XDECREF(boxed_call);
 
   return NULL;