Compilare: user.cpp: In function ‘int main()’: user.cpp:30:28: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s2[ns2]=NULL; ^ user.cpp:46:54: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] i--; c[nr].car[p]=NULL; ^ user.cpp:15:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dir.in", "r", stdin); ^ user.cpp:16:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dir.out", "w", stdout); ^ user.cpp:17:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccTSY7rh.o: In function `main': user.cpp:(.text.startup+0x56): warning: the `gets' function is dangerous and should not be used.