Compilare: main.cpp: In member function 'int Struct::get_val(int)': main.cpp:48:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (dh >= v.size()) { ~~~^~~~~~~~~~~ main.cpp: In function 'void join(Struct&, Struct&)': main.cpp:68:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < to.v.size(); ++i) { ~~^~~~~~~~~~~~~ main.cpp:79:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < from.v.size(); ++i) { ~~^~~~~~~~~~~~~~~ main.cpp: In constructor 'InputReader::InputReader(const char*)': main.cpp:15:35: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buffer, 1, SIZE, in); ^ main.cpp: In member function 'void InputReader::advance()': main.cpp:38:39: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buffer, 1, SIZE, in); ^