/in/foo.c: In function 'main':
/in/foo.c:10:2: 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:10:7: warning: passing argument 1 of 'gets' from incompatible pointer type [-Wincompatible-pointer-types]
  gets(s1);
       ^~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: expected 'char *' but argument is of type 'int *'
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:11:2: 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__;
              ^~~~
/in/foo.c:11:7: warning: passing argument 1 of 'gets' from incompatible pointer type [-Wincompatible-pointer-types]
  gets(s2);
       ^~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: expected 'char *' but argument is of type 'int *'
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:13:11: warning: passing argument 1 of 'length' from incompatible pointer type [-Wincompatible-pointer-types]
  x=length(s1);
           ^~
/in/foo.c:3:5: note: expected 'char *' but argument is of type 'int *'
 int length(char s[]);
     ^~~~~~
/in/foo.c:14:11: warning: passing argument 1 of 'length' from incompatible pointer type [-Wincompatible-pointer-types]
  y=length(s2);
           ^~
/in/foo.c:3:5: note: expected 'char *' but argument is of type 'int *'
 int length(char s[]);
     ^~~~~~
/in/foo.c: In function 'length':
/in/foo.c:24:6: warning: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
  sum=strlen(s);
      ^~~~~~
/in/foo.c:24:6: warning: incompatible implicit declaration of built-in function 'strlen'
/in/foo.c:24:6: note: include '<string.h>' or provide a declaration of 'strlen'
/tmp/ccjjE6hC.o: In function `main':
foo.c:(.text.startup+0x18): warning: the `gets' function is dangerous and should not be used.