I don't know how to export a static variable that is inside a template to my executable.
I'm using entityx library that has a template for components:
Entity.h :
struct BaseComponent {
public:
typedef size_t Family;
protected:
static Family family_counter_; //THIS!!
};
template <typename Derived>
struct Component : public BaseComponent {
public:
typedef ComponentHandle<Derived> Handle;
typedef ComponentHandle<const Derived, const EntityManager> ConstHandle;
private:
friend class EntityManager;
/// Used internally for registration.
static Family family();
};
Entity.cpp:
BaseComponent::Family BaseComponent::family_counter_ = 0;
Now I have my library that links to entityx and uses that: World.hpp:
#include <entityx/entityx.h>
namespace edv {
class Transform : public entityx::Component<Transform> {
public:
Transform();
};
class World {
public:
World();
entityx::Entity createEntity();
private:
entityx::EventManager m_events;
entityx::EntityManager m_entities;
};
}
World.cpp:
#include <Endavant/game/World.h>
#include <iostream>
namespace edv {
Transform::Transform() {
}
World::World(): m_entities(m_events){
}
void World::update() {
}
entityx::Entity World::createEntity() {
auto e = m_entities.create();
e.assign<Transform>();
auto c = e.component<Transform>();
if (c.valid()) {
std::cout<<"createEntity componenthdnlr OK!!"<<e.id()<<std::endl;
} else {
std::cout<<"createEntity componenthdnlr INVALID!!"<<e.id()<<std::endl;
}
return e;
}
}
Now I build an executable "myprogram.exe" that links to my library EDV and to entityx:
#include <Endavant/Root.h>
#include <Endavant/game/World.h>
void test() {
auto entity = edv::Root::get().getWorld().createEntity();
auto comp = entity.component<edv::Transform>();
if (comp.valid()) {
std::cout<<"test componenthndlr VALID!!"<<entity.id()<<std::endl;
} else {
std::cout<<"test componenthndlr INVALID!!"<<entity.id()<<std::endl;
}
}
int main() {
try {
edv::Root::get().init();
test();
edv::Root::get().run();
} catch (std::exception & e) {
std::cout<<e.what()<<std::endl;
}
return 0;
}
When I execute "myprogram.exe" it outputs:
createEntity componenthdnlr OK!!
test componenthndlr INVALID!!
I debugged the application and it seems that there are two instances of "family_counter_" static variable one for my dll, and another for the executable "myprogram.exe".
When I compile the same in Linux, it works as expected:
createEntity componenthdnlr OK!!
test componenthndlr OK!!
So I think it should be something about Windows DLL visibility in GCC. I'm new to this Windows DLL world and I don't know exactly where and what I have to export, to make this work.
I'm using MSYS2 with GCC 5.2.0 to compile this. Thank you
