>K&R C no longer compiles.

    foo@virt-ubuntu:~/c$ gcc --version
    gcc (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406
    Copyright (C) 2016 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    
    foo@virt-ubuntu:~/c$ cat 'k&r.c' 
    #include<stdio.h>
    
    int main(argc, argv)
        int argc;
        char *argv[];
    {
        puts("hello, world!");
        return 0;
    }
    
    foo@virt-ubuntu:~/c$ gcc 'k&r.c' 
    foo@virt-ubuntu:~/c$ ./a.out
    hello, world!