cifre.cpp: In function 'void read()': cifre.cpp:25: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result cifre.cpp:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result cifre.cpp:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result cifre.cpp: In function 'void build_next()': cifre.cpp:39: warning: unused variable 'in' cifre.cpp: In function 'void write()': cifre.cpp:83: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result