Question

What happens if you compile and execute this code?

class A {};

void Destroy(A *&ptr) {
    delete ptr;
    ptr = 0;
}

int main() {
    A *a = new A();
    Destroy(a);
    Destroy(a);
}

Cosmo · Accepted Answer

In Destroy(), a reference to the pointer is passed, then after the first call of this function, the pointer a will become zero. During the second call of Destroy(), a null pointer will be passed to delete. By standard, the delete operator must correctly process the null pointer, so the program will exit successfully. Also, according to the standard, the main function may not accept arguments and may not contain a return statement.

Cosmo · Accepted Answer

The code will be successfully compiled and executed.

Cosmo · Answer

Code will not compile

Cosmo · Answer

Runtime exception will occur

Cosmo · Answer

The code will throw an exception

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