Accidentally breaks C++ Access Rights while computing The Answer to the Ultimate Question of Life, the Universe, and Everything.

Murphy42.cpp

#include <iostream>

// File x.h
// This class was named X to be consistent with http://www.gotw.ca/gotw/076.htm
//
// Its primary purpose is to hold a private value which no one should be able
// to accidentally modify.
class X
{
public:
  X() : private_(1) { /*...*/ }
  int Value() { return private_; }
private:
  int private_;
};



// File Murphy42.cpp

const int NOT_READY_YET = -1;

class BigAnswer : public X
{
public:
    BigAnswer() : answer_to_life_universe_and_everything(NOT_READY_YET) {}
    int answer_to_life_universe_and_everything;
};

class BigQuestion : public BigAnswer
{
public:
    BigQuestion() : question_to_life_universe_and_everything(NOT_READY_YET) {}
    int question_to_life_universe_and_everything;
};


// Uses an enormous supercomputer to find The Answer to the Ultimate Question of
// Life, the Universe, and Everything.
int compute_answer() {
    return 42;
}

// A c-style function to compute the answer_to_life_universe_and_everything and
// to check that it is correct. Output is written to @answers.
// We check for errors by computing @num_answers times and testing whether they
// all come out the same.
// Returns 0 when there are no errors.
int compute_answer_and_check_for_errors(BigAnswer* answers, int num_answers) {
    for (int i=0; i<num_answers; ++i) {
        answers[i].answer_to_life_universe_and_everything = compute_answer();
    }

    // Check for errors (consistency)
    int num_errors = 0;
    for (int i=1; i<num_answers; ++i) {
        if (
            answers[i].answer_to_life_universe_and_everything !=
            answers[0].answer_to_life_universe_and_everything
        ) {
            ++num_errors;
        }
    }
    return num_errors;
}


int main() {
    // We intend to compute the question_to_life_universe_and_everything with
    // these in the near future.
    const int num_error_checks = 10;
    BigQuestion earths[num_error_checks];

    // Before computing the question_to_life_universe_and_everything,
    // let's first check that we can compute the answer correctly.
    int error = compute_answer_and_check_for_errors(earths, num_error_checks);
    if (error) {
        std::cout << "oh no! " << error << std::endl;
        return error;
    }
    std::cout << "Answer computed and checked successfully!" << std::endl;

    // Print out the result of one. We should be able to choose any earth
    // since compute_answer_and_check_for_errors has verified that all the
    // outputs are the same.
    std::cout << "And the answer is: ";
    std::cout << earths[1].Value();  // WAIT, WHAT?!? This is 42. But how?
    std::cout << std::endl;

    return 0;
}