Question

#include <iostream>
struct D{};
struct B{};

struct C
{
    C();
};

struct A
{
    A();
    B * b;
    C * c;
    D * d;

    static A& pInstance()
    {
        static A a;
        return a;
    }
};


A::A()
{
    b = new B;
    c = new C;
    d = new D;
}

C::C()
{
    A::pInstance().b;
}

int main()
{
    A::pInstance();

    std::cin.ignore();

} 

Is there potentially any problems with the above case, as the C constructor call A field while A class not yet construted entirely.

I have this code in production. The application seems to crash randomly at starting, I am wondering if this can be due to this “poor” design.

Answer 1

It’s explicitly stated as Undefined Behavior: (§ 6.7/4) “If control re-enters the declaration recursively while the variable is being initialized, the behavior is undefined.”