Initialise C-structs in C++

Question

I am creating a bunch of C structs so i can encapsulate data to be passed over a dll c interface. The structs have many members, and I want them to have defaults, so that they can be created with only a few members specified.

As I understand it, the structs need to remain c-style, so can't contain constructors. Whats the best way to create them? I was thinking a factory?

Answer 1

struct Foo {
    static Foo make_default ();
};

A factory is overkill. You use it when you want to create instances of a given interface, but the runtime type of the implementation isn't statically known at the site of creation.

Answer 2

The C-Structs can still have member functions. Problems will, however, arise if you start using virtual functions as this necessitates a virtual table somewhere in the struct's memory. Normal member functions (such as a constructor) don't actually add any size to the struct. You can then pass the struct to the DLL with no problems.