Compilare: user.cpp: In function ‘int main()’: user.cpp:24:11: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s[n+1]=NULL; ^ user.cpp:15:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("expresie2.in","r",stdin); ^ user.cpp:16:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("expresie2.out","w",stdout); ^ user.cpp:21:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccfd4K0I.o: In function `main': user.cpp:(.text.startup+0x5e): warning: the `gets' function is dangerous and should not be used.