[bug #48372] read with size 0 from fifo blocks

[Kalle Olavi Niemitalo]

URL:
  <http://savannah.gnu.org/bugs/?48372>

                 Summary: read with size 0 from fifo blocks
                 Project: The GNU Hurd
            Submitted by: kon
            Submitted on: Fri Jul  1 22:00:01 2016
                Category: Hurd Servers
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Standard Compliance
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
         Reproducibility: Every Time
              Size (loc): None
         Planned Release: None
                  Effort: 0.00
Wiki-like text discussion box: 

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Details:

mkfifo da; sleep 1000 > da & rpctrace perl -e 'sysread STDIN, $_, 0' < da

hangs at:  136<--159(pid1132)->io_read (-1 0)

According to antrik, POSIX specifies that read with nbyte==0 must immediately
return 0 or return an error. This could be implemented in libc, libtrivfs,
fifo, or libpipe. It seems best to implement this in fifo or libpipe so that
fifo can still return EBADF if the fifo was not opened for reading.

I filed this as distinct from bug 48371 (for the streamio translator) because
they can be fixed and tested independently.




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