~EntityManager() depends on having a valid EventManager

[iamPHEN]

I ran into a slight usage issue issue with the following App:

struct App {
   App() : em(ev) {}

    EventManager ev;
    EntityManager em;
 }

 int main() {
    App a;
    a.em.create();
    return 0;
 }

What happens here is:

~App() is called ~EventManager() gets called, all signal handlers get destructed. ~EntityManager() calls EntityManager::reset(), which emits EntityDestroyedEvent

This caused a SEGFAULT in a weird spot during EntityManager::emit<entityx::EntityDestroyedEvent, entityx::Entity>(entityx::Entity&&).

Possible solution (not sure whats best) :

• Have EntityManager hold a share_ptr to EventManager.
• Add a destroy_no_events(..) or silent_destroy() for use cases of destroying a entity without a valid EventManager.
• Have users rewrite App such that ~EventManager() comes after ~EntityManager().

[iamPHEN]

As another note: The app is valid when complied on windows with MSVC15 and doesn't segfault on exit.

I'm curious as to why that is, but that's a bit off topic :).

[alecthomas]

According to this post, members should be constructed in the order they appear, and destructed in reverse order. If that is not the case, it seems that this is a compiler bug.

[iamPHEN]

Ah. I was trying to dig for that. Awesome. I'm fine with closing this issue then since the standard recognizes it that way.

Sounds like a MSVC bug then, or me just being lucky that the Signal was still valid after deconstruction of the event manager.

Closing issue.