Compilare: user.cpp: In function ‘int main()’: user.cpp:64:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "qmatrix.out", "w", stdout ); ^ user.cpp: In member function ‘void input_reader::advance()’: user.cpp:22:49: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^ user.cpp: In constructor ‘input_reader::input_reader(const char*, const char*)’: user.cpp:30:45: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^