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Date: Wed, 21 Dec 2022 06:15:27 -0500
To: cygwin AT cygwin DOT com
Subject: open /dev/null O_NOFOLLOW fails with ELOOP
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open /dev/null O_NOFOLLOW fails with ELOOP

Windows 10, 64-bit cygwin

Failed with my existing install, then I ran setup.exe, updated to
latest, and my tests still failed.

a.c
---

#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>

int main (void)
{
    int fd = open("/dev/null", O_RDWR | O_NOFOLLOW, 0);
    if (fd < 0)
        perror("open(/dev/null)");
    return fd;
}


$ gcc a.c ; ./a.exe
open(/dev/null): Too many levels of symbolic links

While troubleshooting this, there were times where it succeeded and then
times where it failed, though it failed most of the time.  It did not
fail (or succeed) randomly, but seemingly in streaks.

Trying to start lighttpd seems to run into this bug reliably,
  $ /usr/sbin/lighttpd -D -f /etc/lighttpd/lighttpd.conf
In the next release of lighttpd, I may end up omitting O_NOFOLLOW
if __CYGWIN__ is defined.

Cheers, Glenn

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