Question

The following code raises a runtime error:

#include <iostream>
#include <iterator>
#include <ext/slist>

class IntList :  public __gnu_cxx::slist<int> {
public:
    IntList() { tail_ = begin(); } // seems that there is a problem here
    void append(const int node) { tail_ = insert_after(tail_, node); }

private:
    iterator tail_;
};

int main() {
    IntList list;

    list.append(1);
    list.append(2);
    list.append(3);

    for (IntList::iterator i = list.begin(); i != list.end(); ++i) {
        std::cout << *i << " ";
    }

    return 0;
}

Seems that the problem is in the constructor IntList(). Is it because it calls the member function begin()?

Answer 1

Looks like You are inserting after end();

In the body of the constructor

IntList() { tail_ = begin(); }

the base class is constructed and it’s members can be called, but for an empty list, it should return end();