How to initialize static members of a class?

Question

I have written this code. It is giving no compile time errors but a runtime error. Can you please tell me what is wrong with this code?

It is giving this runtime error -> strap info: vpid 1: terminated with signal 11

    #include <iostream>

    class Color
    {
    public:
        static Color White, Black, Red, Green, Blue;

        unsigned char red, green, blue;

        static void static_Color();

        Color(unsigned char _red
        , unsigned char _green
        , unsigned char _blue)
        : red(_red), green(_green), blue(_blue)
        {
            static_Color();
        }
        
        Color()
        {
            static_Color();
        }
    };
    
    Color Color::White, Color::Black
    , Color::Red, Color::Green, Color::Blue;
    
    void Color::static_Color()
    {
        static bool called_before = false;

        if(called_before)
            return;

        Color::White = Color(255, 255, 255);
        Color::Black = Color(0, 0, 0);
        Color::Red = Color(255, 0, 0);
        Color::Green = Color(0, 255, 0);
        Color::Blue = Color(0, 0, 255);

        called_before = true;
    }
    
    int main()
    {
        std::cout << (int) Color::Red.red;
    }

A needed feature static constructor.

Answer 1

You don't need a static_Color() function. Just initialize them with the proper values where the static colors are defined:

class Color {
public:
    static Color White, Black, Red, Green, Blue;

    unsigned char red = 0, green = 0, blue = 0;

    Color(unsigned char _red, unsigned char _green, unsigned char _blue)
        : red(_red), green(_green), blue(_blue) {}

    Color() = default;
};

// Here:
Color Color::White = Color(255, 255, 255);
Color Color::Black = Color(0, 0, 0);
Color Color::Red = Color(255, 0, 0);
Color Color::Green = Color(0, 255, 0);
Color Color::Blue = Color(0, 0, 255);

Right now, your the call to static_Color() in your constructor causes infinite recursion since every construction of a Color will cause a call to static_Color() that will again construct more Colors.

---

An alternative to having static member variables is to make some constants in your namespace. I've called the namespace Color too. You figure out a better one:

namespace Color {
class Color {
public:
    unsigned char red = 0, green = 0, blue = 0;

    constexpr Color(unsigned char _red, unsigned char _green, unsigned char _blue)
        : red(_red), green(_green), blue(_blue) {}

    Color() = default;
};

inline constexpr Color White = Color(255, 255, 255);
inline constexpr Color Black = Color(0, 0, 0);
inline constexpr Color Red = Color(255, 0, 0);
inline constexpr Color Green = Color(0, 255, 0);
inline constexpr Color Blue = Color(0, 0, 255);
}  // namespace Color