#include <wchar.h>

struct stringtree
{
    struct child
    {
        enum child_kind {
            ck_cstr,
            ck_string,
            ck_stringtree,
        } kind;
        
        union {
            const wchar_t* cstr;
            
            struct string* string;
            
            struct stringtree* stringtree;
        };
        
        struct child *prev, *next;
    } *head, *tail;
    
    unsigned refcount;
};