JuniorTheoryCommon

What does the program print?

C++

#include <iostream>
#include <memory>

int main() {
    auto a = std::make_shared<int>(5);
    auto b = a;
    {
        auto c = b;
        std::cout << a.use_count() << ' ';
    }
    std::cout << a.use_count() << '\n';
}

3 2

Expecting 3 3: c is destroyed at the end of its block, and every destroyed owner lowers the count by one.
Expecting 2 2: c copies b, which shares the same int with a, so use_count() counts all three owners.

At which line of this program is the int created by std::make_shared deleted?
How would a std::weak_ptr made from a change the numbers this program prints?

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JuniorTheoryCommon

What does the program print?

C++

#include <iostream>
#include <memory>

int main() {
    auto a = std::make_shared<int>(5);
    auto b = a;
    {
        auto c = b;
        std::cout << a.use_count() << ' ';
    }
    std::cout << a.use_count() << '\n';
}

3 2

Expecting 3 3: c is destroyed at the end of its block, and every destroyed owner lowers the count by one.
Expecting 2 2: c copies b, which shares the same int with a, so use_count() counts all three owners.

At which line of this program is the int created by std::make_shared deleted?
How would a std::weak_ptr made from a change the numbers this program prints?

Back to questions Open topic in roadmap →Answer it yourself — Quiz