Compilare: user.cpp: In function ‘void prefix(std::string)’: user.cpp:16: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:59: warning: comparison between signed and unsigned integer expressions user.cpp:28: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:33: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result user.cpp:34: warning: ignoring return value of ‘char* fgets(char*, int, 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 ‘int main()’ at user.cpp:33: /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 In function ‘char* fgets(char*, int, FILE*)’, inlined from ‘int main()’ at user.cpp:34: /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