cifru1.cpp: In constructor 'instream::instream(const char*)': cifru1.cpp:15: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result cifru1.cpp: In constructor 'instream::instream(const char*)': cifru1.cpp:15: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result cifru1.cpp: In constructor 'instream::instream(const char*)': cifru1.cpp:15: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result cifru1.cpp: In member function 'void instream::advance()': cifru1.cpp:37: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result