Dereference a pointer only if it is not null

ifnotnull.hpp

#pragma once

// Dereference a pointer only if it is not null
#define ifnotnull(p) for (auto* p__ = p; p__ != nullptr; p__ = nullptr) (*p__)

usage_example.cpp

// Try Online: http://coliru.stacked-crooked.com/a/df2a5066990e150f

#include <iostream>

// Dereference a pointer only if it is not null
#define ifnotnull(p) for (auto* p__ = p; p__ != nullptr; p__ = nullptr) (*p__)

struct Foo
{
    void bar() const { std::cout << "hello\n"; }
};

int main() 
{
    Foo foo;
    
    ifnotnull(&foo).bar();                        // Prints "hello"
    ifnotnull(static_cast<Foo*>(nullptr)).bar();  // Doesn't do anything
}