Compilare: user.cpp: In function ‘int main()’: user.cpp:49:11: warning: unused variable ‘j’ [-Wunused-variable] int i,j; ^ user.cpp: In member function ‘void instream::advance()’: user.cpp:40:48: 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 ‘instream::instream(const char*)’: user.cpp:14:44: 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); ^