cppNull / UndefinedMedium

Use after move on std::unique_ptr

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BugFind the bug and fix the code

What it should do

Transfer resource ownership and return resource value. Example: transferUniqueOwnership(50) -> 50

What happens instead

Segmentation fault: dereferencing null pointer after std::move

#include <iostream>
#include <memory>

int transferUniqueOwnership(int val) {
    auto p1 = std::make_unique<int>(val);
    auto p2 = std::move(p1);
    // p1 has been moved from and now holds nullptr
    return *p1;
}

int main() {
    std::cout << transferUniqueOwnership(50) << std::endl;
    return 0;
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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This bug belongs to the null and undefined errors pattern

Cannot read properties of undefined, NoneType has no attribute, NaN appearing from nowhere.

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#include <iostream> #include <memory> int transferUniqueOwnership(int val) { auto p1 = std::make_unique<int>(val); auto p2 = std::move(p1); // p1 has been moved from and now holds nullptr return *p1; } int main() { std::cout << transferUniqueOwnership(50) << std::endl; return 0; }

Use after move on std::unique_ptr

What it should do

What happens instead

More null and undefined errors to practise

Use after move on std::unique_ptr

What it should do

What happens instead

More null and undefined errors to practise