What's wrong with this code?

[bearophile]

Sean Eskapp:

> I had some code that was segfaulting, so I rewrote the basic idea as a
> fibonacci function, and lo and behold, it still segfaults. Why, and how to fix?

Two versions:

struct Fib {
    private const Fib* left, right;

    this(in Fib* left=null, in Fib* right=null) {
        this.left = left;
        this.right = right;
    }

    const int evaluate() {
        if (left is null)
            return 1;
        else
            return left.evaluate() + right.evaluate();
    }
}

Fib* bar(int n) {
    if (n == 0 || n == 1)
        return new Fib();
    else
        return new Fib(bar(n - 1), bar(n - 2));
}

void main() {
    auto x = bar(5);
    assert(x.evaluate() == 8);
}

--------------------

struct Fib {
    private const Fib* left, right;

    this(in Fib* left=null, in Fib* right=null) {
        this.left = left;
        this.right = right;
    }

    const int evaluate() {
        if (left is null)
            return 1;
        else
            return left.evaluate() + right.evaluate();
    }
}

Fib* bar(int n) {
    if (n == 0 || n == 1)
        return new Fib();
    else
        return new Fib(bar(n - 1), bar(n - 2));
}

void main() {
    auto x = bar(5);
    assert(x.evaluate() == 8);
}

Bye,
bearophile