Compilare: user.cpp: In function ‘void read()’: user.cpp:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:29: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘int cb1(int, int)’: user.cpp:56: warning: comparison between signed and unsigned integer expressions user.cpp:58: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int cb2(int, int)’: user.cpp:68: warning: comparison between signed and unsigned integer expressions user.cpp:70: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:115: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:116: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result In file included from /usr/include/stdio.h:910, from user.cpp:1: In function ‘char* fgets(char*, int, FILE*)’, inlined from ‘void read()’ at user.cpp:29: /usr/include/bits/stdio2.h:253: warning: call to ‘__fgets_chk_warn’ declared with attribute warning: fgets called with bigger size than length of destination buffer