Cygwin unlinked /proc/self/fd/* is ENOENT

test.c

#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <alloca.h>

int main() {
	char path[] = "tmp";
	int r;

	int fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_TRUNC, 0600);
	printf("open(\"%s\", ...) = %d\n", path, fd);
	r = unlink(path);
	printf("unlink(\"%s\") = %d\n", path, r);

	char *buf = alloca(20);
	sprintf(buf, "/proc/self/fd/%d", fd);
	r = open(buf, O_RDONLY);
	printf("open(\"%s\", ...) = %d\n", buf, r);

	return 0;
}

test.log

Linux$ gcc -Wall test.c -o x && ./test
open("tmp", ...) = 3
unlink("tmp") = 0
open("/proc/self/fd/3", ...) = 4

Cygwin$ gcc -Wall test.c -o x && ./test
open("tmp", ...) = 3
unlink("tmp") = 0
open("/proc/self/fd/3", ...) = -1