Bug in Control-d handling?

[Ken Brown <kbrown@cornell.edu>]

Consider the following program, which reads from standard input a line at a time 
and then echoes the input back to the terminal:

$ cat cat_line.c
#include <stdio.h>

int main ()
{
   char buf[BUFSIZ];

   while (fgets (buf, BUFSIZ, stdin))
     fputs (buf, stdout);
}

Run the program, type one or more characters (without hitting Enter), and type 
Ctrl-d until the program exits.  What I expect is that nothing visible happens 
on the first Ctrl-d [but the input is sent to the internal stdin buffer], and 
that the input is echoed and the program exits after the second Ctrl-d [the 
program sees EOF].  This is what happens on Linux.  On Cygwin, however, the 
program keeps running after the second Ctrl-d and doesn't exit until Ctrl-d is 
pressed a third time.

I observed this problem because of a failing Emacs test, in which the program 
"rev" was not seeing EOF after being sent Ctrl-d; "rev" does something like the 
test case above, but using fgetws instead of fgets.

Ken