/in/foo.c: In function 'main':
/in/foo.c:6:4: warning: 'gets' is deprecated [-Wdeprecated-declarations]
    char s1[N]; gets(s1);
    ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:7:4: warning: 'gets' is deprecated [-Wdeprecated-declarations]
    char s2[N]; gets(s2);
    ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:8:4: warning: 'gets' is deprecated [-Wdeprecated-declarations]
    char s3[N]; gets(s3);
    ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/tmp/ccHCPhjp.o: In function `main':
foo.c:(.text.startup+0x26): warning: the `gets' function is dangerous and should not be used.