cppScope errorMedium

Resource Leak Detected in Derived Class Destruction

Time: 0:00

BugFind the bug and fix the code

What it should do

Process a list of shapes and print their areas. Example: processShapes(shapes) -> prints areas of shapes

What happens instead

Valgrind reports invalid free() or memory leak when processing shapes.

#include <iostream>\n#include <vector>\nusing namespace std;\n\nclass Shape {\npublic:\n    virtual double getArea() const { return 0.0; }\n};\n\nclass Circle : public Shape {\nprivate:\n    double radius;\npublic:\n    Circle(double r) : radius(r) {}\n    double getArea() const override { return 3.14159 * radius * radius; }\n};\n\nvoid processShapes(const vector<Shape*>& shapes) {\n    for (const auto& shape : shapes) {\n        cout << "Area: " << shape->getArea() << "\n";\n    }\n}\n\nint main() {\n    vector<Shape*> shapes;\n    shapes.push_back(new Circle(5.0));\n    processShapes(shapes);\n    for (auto shape : shapes) {\n        delete shape;\n    }\n    return 0;\n}

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

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Hints

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Hint 3

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This bug belongs to the scope and closure bugs pattern

Every callback reports the last value, a counter never increments, UnboundLocalError on a variable you can see.

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#include <iostream>\n#include <vector>\nusing namespace std;\n\nclass Shape {\npublic:\n virtual double getArea() const { return 0.0; }\n};\n\nclass Circle : public Shape {\nprivate:\n double radius;\npublic:\n Circle(double r) : radius(r) {}\n double getArea() const override { return 3.14159 * radius * radius; }\n};\n\nvoid processShapes(const vector<Shape*>& shapes) {\n for (const auto& shape : shapes) {\n cout << "Area: " << shape->getArea() << "\n";\n }\n}\n\nint main() {\n vector<Shape*> shapes;\n shapes.push_back(new Circle(5.0));\n processShapes(shapes);\n for (auto shape : shapes) {\n delete shape;\n }\n return 0;\n}

Resource Leak Detected in Derived Class Destruction

What it should do

What happens instead

More scope and closure bugs to practise

Resource Leak Detected in Derived Class Destruction

What it should do

What happens instead

More scope and closure bugs to practise