Is there a way in C++ to preinitialize structure or class without a constructors?

Question

I mean: I've a bunch of various structures/classes and all this a splendor shall be initialized with known in advance values. Those structures/classes will never be used other way except the preinitialized one, so there is no any need for constructor -- it's just a waste of extra memory, extra CPU cycles in program, and extra space in source code.

Answer 1

If you have access to a C++11 compiler, you can mark your constructors as constexpr to have them run at compile time. The benefit of this is that way down the road you can still construct your objects at runtime. e.g.

struct Point2D {
    constexpr Point2D(int x, int y) : x_{x}, y_{y} {}
    int x_, y_;
};

And now you can use Point2D's constructor to initialize it at compile time, instead of runtime:

Point2D p{3, 4}; // no runtime overhead.

Answer 2

Structures and classes can be initialized, in limited circumstances.

struct splendor {
    int i, j;
    char *name;
};

splendor iforus = { 1, 2, "Extra!" };

Additionally, if you never need the name of the type of the structure:

struct {
    int k;
    float q;
} anon_e_mouse = { 1, 2.3 };