/in/foo.c: In function 'Diff':
/in/foo.c:6:3: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   gets(s);
   ^~~~
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:7:3: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
   for(i=0;i<strlen(s);i++)
   ^~~
/in/foo.c:12:4: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
    return b-a;
    ^~~~~~
/in/foo.c: In function 'main':
/in/foo.c:17:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  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:18:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  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__;
              ^~~~
/tmp/ccExkrmb.o: In function `Diff':
foo.c:(.text+0x5): warning: the `gets' function is dangerous and should not be used.