Compilare: user.cpp: In function ‘int main()’: user.cpp:20:25: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] a[strlen(a)]=NULL; ^ user.cpp:22:25: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] b[strlen(b)]=NULL; ^ user.cpp:10:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("password.in","r",stdin); ^ user.cpp:11:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("password.out","w",stdout); ^ user.cpp:12:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); n=strlen(s); m=n; ^ /tmp/ccFUfr2N.o: In function `main': user.cpp:(.text.startup+0x63): warning: the `gets' function is dangerous and should not be used.