back11: undefined behaviour (reported by llvm 18)

[matthijs]

Hi,

Compiler: clang++-18
Boost: version 1.86.0

I have the following statemachine:

#include <iostream>

#include <boost/msm/back11/state_machine.hpp>
#include <boost/msm/front/puml/puml.hpp>
#include <boost/msm/front/state_machine_def.hpp>

namespace msm = boost::msm;
using namespace msm::front;
using namespace msm::front::puml;

namespace boost::msm::front::puml {

// Actions
template <> struct Action<by_name("a_connected")> {
  template <typename Event, typename FSM, typename SourceState,
            typename TargetState>
  void operator()(const Event &, FSM &, SourceState &, TargetState &) {
    std::cout << "server connected" << std::endl;
  }
};
} // namespace boost::msm::front::puml

struct server_ : public msm::front::state_machine_def<server_> {
  int chain_id{0};
  int job_id{0};
  BOOST_MSM_PUML_DECLARE_TABLE(R"(
@startuml server
state Server {
[*]       --> Initial
Initial   --> Connected : connected / a_connected
}
@enduml
)")
};
using server = msm::back11::state_machine<server_>;
using connected = Event<by_name("connected")>;

int main(int, char **) {

  // server
  server sm;
  sm.process_event(connected{});

  return 0;
}

When compiling and executing:

$ /usr/bin/clang++-18 -isystem /home/matthijs/src/boost/boost_1_86_0 -fno-omit-frame-pointer -O1 -fsanitize=address,undefined,pointer-compare,pointer-subtract,leak -fsanitize-address-use-after-scope -Wall -Wextra -g -std=gnu++20 ../main.cpp -o main
$ ./main
/home/matthijs/src/boost/boost_1_86_0/boost/msm/back11/state_machine.hpp:2171:21: runtime error: call to function boost::msm::back11::state_machine<server_, void, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_>::a_row_<boost::msm::front::Row<boost::msm::front::puml::State<2389040076u, boost::fusion::vector<>, boost::fusion::vector<>, boost::fusion::vector<>>, boost::msm::front::puml::Event<3846760266u>, boost::msm::front::puml::State<1740203497u, boost::fusion::vector<>, boost::fusion::vector<>, boost::fusion::vector<>>, boost::msm::front::puml::Action<2978207285u>, boost::msm::front::none>>::execute(boost::msm::back11::state_machine<server_, void, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_>&, int, int, boost::msm::front::puml::Event<3846760266u> const&) through pointer to incorrect function type 'boost::msm::back::HandledEnum (*)(boost::msm::back11::state_machine<server_> &, int, int, boost::msm::front::puml::Event<3846760266> &)'
/home/matthijs/src/boost/boost_1_86_0/boost/msm/back11/state_machine.hpp:590: note: boost::msm::back11::state_machine<server_, void, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_>::a_row_<boost::msm::front::Row<boost::msm::front::puml::State<2389040076u, boost::fusion::vector<>, boost::fusion::vector<>, boost::fusion::vector<>>, boost::msm::front::puml::Event<3846760266u>, boost::msm::front::puml::State<1740203497u, boost::fusion::vector<>, boost::fusion::vector<>, boost::fusion::vector<>>, boost::msm::front::puml::Action<2978207285u>, boost::msm::front::none>>::execute(boost::msm::back11::state_machine<server_, void, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_, boost::parameter::void_>&, int, int, boost::msm::front::puml::Event<3846760266u> const&) defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/matthijs/src/boost/boost_1_86_0/boost/msm/back11/state_machine.hpp:2171:21
server connected

I am not sure if this is a serious problem. If you need more information let me know.

Regards, Matthijs

[PiotrNycz]

I have the same problem with "back" -- not "back11" - with clang UB-sanitizer starting from version 1.86 - I do not know when it started - my previous version of boost was 1.78 (it worked there):

runtime error: call to function boost::msm::back::dispatch_table<boost::msm::back::state_machine<.>>::execute(.) through pointer to incorrect function type.*

AFAICS - the incorrectness of function --> function pointers is due the fact that pointer to function expects "const Event&" while this execute function expects "Event&" (not const). But I am not 100% I did not mistake in this. I just add it to suppression list and "forgot"