Compilare: main.cpp: In function 'int main()': main.cpp:54:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen(iname,"r",stdin); ^ main.cpp:55:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen(oname,"w",stdout); ^ main.cpp:56:33: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fgets(s2+1,sizeof(s2),stdin); ^ In file included from /usr/include/stdio.h:936:0, from /usr/include/c++/6/cstdio:42, from main.cpp:1: In function 'char* fgets(char*, int, FILE*)', inlined from 'int main()' at main.cpp:56:33: /usr/include/x86_64-linux-gnu/bits/stdio2.h:261:58: warning: call to '__fgets_chk_warn' declared with attribute warning: fgets called with bigger size than length of destination buffer return __fgets_chk_warn (__s, __bos (__s), __n, __stream); ^