Compilare: user.cpp: In function ‘int64_t check_prefize(int64_t, int64_t, const string&)’: user.cpp:10:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int idx = prefixsize; idx < B.size(); ++idx) ^ user.cpp: In function ‘int main()’: user.cpp:89:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (auto numbits = 1; numbits < B.size() && !done; ++numbits) ^