Bug when reading from a non-blocking pipe file descriptor, whilethe opposite end (the writing pipe file descriptor) is closed.

Sun Jan 21 09:04:00 GMT 2001

The following is the C program to regenerate this bug.
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
void test_func(int n1, int n2) {
 int input_from_child[2];
 pipe(input_from_child);
 if (fork()) {
 char buf[20];
 close(input_from_child[1]);
 fcntl(input_from_child[0], F_SETFL, O_NONBLOCK);
 sleep(n1);
 printf("%d\n", read(input_from_child[0], buf, sizeof(buf)));
 } else {
 close(input_from_child[0]);
 dup2(input_from_child[1], 1);
 close(input_from_child[1]);
 sleep(n2);
 exit(0);
 };
};
int main() {
 test_func(1, 0);
 test_func(1, 2);
 return 0;
};
When compile and run on linux, the output of running this program should
be as follow.
0
-1
But when compile and run using cygwin, the output will be as follow.
-1
-1
The latter case is a bug on cygwin. Because when calling 
read(input_from_child[0], buf, sizeof(buf)) from test_func(1, 0), the
file descriptor input_from_child[0] should be in the end of file status
that should cause the read(...) to return 0.
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