Null coalescense in C++ a bit like in C#, but admittedly not as good.

NullCoalescense.cpp

#include <iostream>
using namespace std;

#define Q(a, b) ([&](){ auto val = (a); if (val) (val->b); }());
#define QQ(a, b) ([&](){ auto val = (a); return ((val) == NULL ? (b) : (val)); }()) 

class A {
    public: void sayHello() { cout << "Hello World\n"; }
};

int main()
{
    A* nullPtr = NULL;
    A* goodPtr = new A();
    
    Q( goodPtr,sayHello() );
    Q( nullPtr,sayHello() );
    
    QQ( nullPtr, goodPtr )->sayHello();
    QQ( goodPtr, nullPtr )->sayHello();
    QQ( nullPtr, QQ( nullPtr, QQ( nullPtr, goodPtr ) ) )->sayHello();
}

Q is like the C# 'maybeNullObj.?member'
QQ is like the C# 'maybeNull ?? backup'
NOTE: Q does not return anything, so cannot stack.