Compilare: user.cpp: In function ‘int uc(int)’: user.cpp:9:15: warning: statement has no effect [-Wunused-value] if(e==0) e==4; ~^~~ user.cpp: In function ‘int main()’: user.cpp:28:9: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(s); ^~~~ In file included from /usr/include/c++/6/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^~~~ user.cpp:28:15: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(s); ^ In file included from /usr/include/c++/6/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^~~~ user.cpp:18:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cifra.in","r",stdin); ^ user.cpp:19:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cifra.out","w",stdout); ^ user.cpp:22:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&t); ^ user.cpp:28:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccgSGpeB.o: In function `main': user.cpp:(.text.startup+0x142): warning: the `gets' function is dangerous and should not be used.