#include <iostream>
 
    struct A {};
 
    A a, b, c;
 
    A* ptr = &a;
 
    void report(A* p) {
        std::cout << (void*) &a << ", " << (void*) &b << ", " << (void*) &c
                  << ": " << (void*) p << "\n";
    }
 
    int f() {
        std::cout << "f() ";
        report(ptr);
    }
 
    int main() {
        report(ptr);
        if (ptr != nullptr) {
            A* ptr = &b;
            report(ptr);
            if (ptr != nullptr) {
                A* ptr = &c;
                report(ptr);
            }
            report(ptr);
        }
        report(ptr);
    }

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