#2212: callback: fix problem with Args/Params conflict incorrect mess…

…age type
DARMA-tasking · Nov 29, 2023 · ae4bae5 · ae4bae5
1 parent 05bb801
commit ae4bae5
Showing 1 changed file with 26 additions and 5 deletions.
diff --git a/src/vt/pipe/callback/cb_union/cb_raw_base.h b/src/vt/pipe/callback/cb_union/cb_raw_base.h
@@ -232,7 +232,8 @@ struct CallbackTyped : CallbackRawBaseSingle {
 
   template <typename... Params>
   void sendTuple(std::tuple<Params...> tup) {
-    using MsgT = messaging::ParamMsg<std::tuple<std::decay_t<Params>...>>;
+    using Trait = CBTraits<Args...>;
+    using MsgT = messaging::ParamMsg<typename Trait::TupleType>;
     auto msg = vt::makeMessage<MsgT>();
     msg->setParams(std::move(tup));
     CallbackRawBaseSingle::sendMsg<MsgT>(msg);
@@ -242,10 +243,30 @@ struct CallbackTyped : CallbackRawBaseSingle {
   void send(Params&&... params) {
     using Trait = CBTraits<Args...>;
     if constexpr (std::is_same_v<typename Trait::MsgT, NoMsg>) {
-      using MsgT = messaging::ParamMsg<std::tuple<std::decay_t<Params>...>>;
-      auto msg = vt::makeMessage<MsgT>();
-      msg->setParams(std::forward<Params>(params)...);
-      CallbackRawBaseSingle::sendMsg<MsgT>(msg);
+      // We have to go through some tricky code to make the MsgProps case work
+      // If we use the type for Params to send, it's possible that we have a
+      // type mismatch in the actual handler type. A possible edge case is when
+      // a char const* is sent, but the handler is a std::string. In this case,
+      // the ParamMsg will be cast incorrectly during the virual dispatch to a
+      // collection because callbacks don't have the collection type. Thus, the
+      // wrong ParamMsg will be cast to which requires serialization, leading to
+      // a failure.
+      if constexpr (sizeof...(Params) == sizeof...(Args) + 1) {
+        using MsgT = messaging::ParamMsg<
+          std::tuple<
+            std::decay_t<std::tuple_element_t<0, std::tuple<Params...>>>,
+            std::decay_t<Args>...
+          >
+        >;
+        auto msg = vt::makeMessage<MsgT>();
+        msg->setParams(std::forward<Params>(params)...);
+        CallbackRawBaseSingle::sendMsg<MsgT>(msg);
+      } else {
+        using MsgT = messaging::ParamMsg<typename Trait::TupleType>;
+        auto msg = vt::makeMessage<MsgT>();
+        msg->setParams(std::forward<Params>(params)...);
+        CallbackRawBaseSingle::sendMsg<MsgT>(msg);
+      }
     } else {
       using MsgT = typename Trait::MsgT;
       auto msg = makeMessage<MsgT>(std::forward<Params>(params)...);