Error/crash when running the simple example.

[tonyvsuk]

Thanks for this, it might turn out to be really useful.

I'm using MS Visual Studio, and when I try and run the simple example, it crashes with the error "vector iterators incompatible".

This happens in the iterator structure.

Any ideas what could be wrong?

All the best,

Tony.

[mottosso]

I also stumbled upon this, and narrowed it down to an iterator accessing elements outside of the valid range. This should patch things up.

utils.hpp

• drag/include/drag/detail/utils.hpp

  Line 15 in a7fc1ff

  template<typename T>

template<typename T>
struct chain_range {
    const T& first;
    const T& second;

    chain_range(const T& first, const T& second) : first(first), second(second) {}

    struct iterator {
        using It = typename T::const_iterator;
        It curr;
        It first_end;
        It second_begin;
        It second_end;
        bool in_first;

        iterator(It first_begin, It first_end, It second_begin, It second_end)
            : first_end(first_end), second_begin(second_begin), second_end(second_end)
        {
            // If the first range is non-empty, start there; otherwise start in second.
            if (first_begin != first_end) {
                curr = first_begin;
                in_first = true;
            } else {
                curr = second_begin;
                in_first = false;
            }
        }

        auto operator*() const -> typename T::value_type {
            // This assert will fire if you try to dereference an iterator at end.
            assert((in_first ? curr != first_end : curr != second_end) &&
                   "Dereferencing end iterator in chain_range");
            return *curr;
        }

        iterator& operator++() {
            if (in_first) {
                ++curr;
                if (curr == first_end) {
                    in_first = false;
                    curr = second_begin;
                }
            } else {
                ++curr;
            }
            return *this;
        }

        friend bool operator==(const iterator& lhs, const iterator& rhs) {
            return lhs.in_first == rhs.in_first && lhs.curr == rhs.curr;
        }

        friend bool operator!=(const iterator& lhs, const iterator& rhs) {
            return !(lhs == rhs);
        }
    };

    iterator begin() const {
         return iterator(first.begin(), first.end(), second.begin(), second.end());
    }

    iterator end() const {
         return iterator(first.end(), first.end(), second.end(), second.end());
    }
};