Heap corruption. Need some eyes on this (C++)

typedef class screen_info {
public:
    int index;
    canvas_t icon;
    label_t value;
    canvas_t bar;
    graph_buffer_t graph;
    screen_packet_t packet;
    screen_info* next;
    char value_sz[64];
    char old_format[16];
    float old_value_max;
    screen_info();
    screen_info(const screen_info& rhs);
    screen_info& operator=(const screen_info& rhs);
    virtual ~screen_info();
} screen_info_t;
...

screen_t main_screen;
screen_info_t* first_segment = nullptr;
screen_info_t* tail_segment = nullptr;

screen_info::screen_info() : index(-1),icon(main_screen),value(main_screen),bar(main_screen), graph(), packet(), next(nullptr) {

}
screen_info::screen_info(const screen_info& rhs) : index(rhs.index), icon(rhs.icon), value(rhs.value), bar(rhs.bar), graph(rhs.graph), packet(rhs.packet), next(rhs.next) {

}
screen_info& screen_info::operator=(const screen_info& rhs) {
    index = rhs.index;
    icon = rhs.icon;
    value = rhs.value;
    bar = rhs.bar;
    graph = rhs.graph;
    packet = rhs.packet;
    next = rhs.next;
    return *this;
}
screen_info::~screen_info() {
    icon.on_paint(nullptr);
    bar.on_paint(nullptr);
    graph.clear();
}

screen_info_t* segment_add() {
    auto result = new screen_info_t();
    if(first_segment==nullptr) {
        first_segment = result;
        tail_segment = result;
        return result;
    }
    if(result==nullptr) { return result; }
    tail_segment->next = result;
    tail_segment = result;
    return result;
}
size_t segment_count() {
    screen_info_t* seg=first_segment;
    size_t result = 0;
    while(seg!=nullptr) {
        seg=seg->next;
        ++result;
    }
    return result;
}
void segment_clear_all() {
    screen_info_t* seg=first_segment;
    while(seg!=nullptr) {
        screen_info_t* n = seg->next;
        delete seg;
        seg=n;
    }
    first_segment = nullptr;
    tail_segment = nullptr;
}