Compilare: user.cpp: In function ‘bool rewrite()’: user.cpp:54:10: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s[j] = NULL; ^ user.cpp:55:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:131:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("bool.in", "r", stdin); ^ user.cpp:132:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("bool.out", "w", stdout); ^ user.cpp:134:14: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (s1); ^ user.cpp:136:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d ", &n); ^ user.cpp:140:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%c", &x); ^ /tmp/ccLZF3gm.o: In function `main': user.cpp:(.text.startup+0x59): warning: the `gets' function is dangerous and should not be used.