/in/foo.c:36:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:39:12: warning: passing argument 1 of 'encrypt' makes pointer from integer without a cast [-Wint-conversion]
    encrypt((char) a[30],(char) b[30]);
            ^
/in/foo.c:22:6: note: expected 'char *' but argument is of type 'char'
 void encrypt(char a[],char b[])
      ^~~~~~~
/in/foo.c:39:25: warning: passing argument 2 of 'encrypt' makes pointer from integer without a cast [-Wint-conversion]
    encrypt((char) a[30],(char) b[30]);
                         ^
/in/foo.c:22:6: note: expected 'char *' but argument is of type 'char'
 void encrypt(char a[],char b[])
      ^~~~~~~
/in/foo.c:39:12: warning: array subscript is above array bounds [-Warray-bounds]
    encrypt((char) a[30],(char) b[30]);
            ^~~~~~~~~~~~