Compilare: user.cpp: In function ‘long int apel(char*)’: user.cpp:142:16: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] *s = NULL; ^ user.cpp: In function ‘int main()’: user.cpp:23:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apel.in","r",stdin); ^ user.cpp:24:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apel.out","w",stdout); ^ user.cpp: In function ‘void build()’: user.cpp:40:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(S); ^ /tmp/cc5X84IH.o: In function `build()': user.cpp:(.text+0x2d): warning: the `gets' function is dangerous and should not be used.