Draup

This is Draup, a compile-time plugin registration system in C++17. Draup is simple to use, and since everything is computed at compile time, Draup should add no runtime overhead to your program.

Usage

You just need to include draup.hpp from all files where you use Draup. Then, you can register classes in the header files in which you declare them (or anywhere else, really). You can later get a list of all registered classes and perform some action on them (instatiate an object, call a static method, …)

Consider this plugin.hpp file that declares, defines and registers two very simple plugin classes:

class MyPlugin {
public:
	static const char * get_name() {
		return "MyPlugin";
	}
};

DRAUP_REGISTER(MyPlugin);

class MyOtherPlugin {
public:
	static const char * get_name() {
		return "MyOtherPlugin";
	}
};

DRAUP_REGISTER(MyOtherPlugin);

Note that the calls to DRAUP_REGISTER must be in the outermost namespace scope.

Now, after including plugin.hpp somewhere, you can do this:

DRAUP_FOR_EACH([&](auto type_container) {
	using plugin = typename decltype(type_container)::type;
	std::cout << "Plugin registered: " << plugin::get_name() << std::endl;
});

This should output:

Plugin registered: MyPlugin
Plugin registered: MyOtherPlugin

Everything is built at compile time, there are no pointers being juggled, no objects being created, nothing.

Requirements

Draup uses C++17 plus the __COUNTER__ macro. Thus, you will need a fairly recent compiler (GCC 7.0 or clang 5.0 should do).