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Postings from March 2000
At 19:16 +0200 2000-03-29, Mark Kettenis wrote:
>On the Hurd, pipes are implemented in the same way as in BSD 4.4.
>They're bidirectional and implemented using sockets. S_ISFIFO() will
>probably return false on the ends, since it only checks for FIFO-ness
>and not for the ends being sockets (S_ISSOCK() will return true). So
>there is indeed a problem with POSIX-compliance.
On MachTen, the file type is zero for pipe ends -- they are not even
being marked as being sockets. If they were, S_ISFIFO would succeed
because of the rather tacky contents of sys/stat.h:
* @(#)stat.h 8.6 (Berkeley) 3/8/94
...
#define S_IFIFO 0010000 /* named pipe (fifo) */
...
#define S_IFSOCK 0140000 /* socket */
...
#define S_ISFIFO(m) ((m & 0170000) == 0010000 || \
(m & 0170000) == 0140000) /* fifo or socket */
...
#ifndef _POSIX_SOURCE
...
#define S_ISSOCK(m) ((m & 0170000) == 0010000 || \
(m & 0170000) == 0140000) /* fifo or socket */
#endif
The fact that MachTen appears to be trying to kludge around the
issue, yet still fails, leads me conclude that it's buggy. I hope
the Hurd does better. Can you tell me what octal filetype my test
program reports, and what sys/stat.h maps that number to?
>However, I disagree that this is something that Perl should not work
>around. There is a long history of pipes being implemented using
>sockets in BSD, and they're bidirectional since at least BSD 4.4. So
>there will be quite a few systems out there that implement pipes that
>way. We'll probably fix the Hurd to follow POSIX (and Linux) a bit
>more closely, but that might not happen to other systems.
I wouldn't mind seeing a work-around on systems which, for historical
reasons, identify pipe-ends as sockets; but I'm reluctant to put in a
hack to accommodate systems which don't bother to identify pipe-ends
at all. That said, the comment at line 459 in doio.c suggests that
MachTen's not alone in being slapdash:
IoTYPE(io) = 's'; /* some OS's return 0 on fstat()ed socket */
/* but some return 0 for streams too, sigh */
Do feel free to submit a patch: I'm fighting other stuff just now.
--
Dominic Dunlop
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