Compilare: user.cpp: In function ‘int main()’: user.cpp:28:16: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] char chr = NULL; ^ user.cpp:28:10: warning: unused variable ‘chr’ [-Wunused-variable] char chr = NULL; ^ user.cpp:23:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("abc2.in" ,"r", stdin); ^ user.cpp:24:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("abc2.out" ,"w", stdout); ^ user.cpp:29:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s + 1); ^ user.cpp:31:18: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir + 1); ^ user.cpp:43:26: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir + 1); ^ user.cpp:63:22: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir + 1); ^ /tmp/cc1cmZnj.o: In function `main': user.cpp:(.text.startup+0xe1): warning: the `gets' function is dangerous and should not be used.