[Bug 210288] File descriptors created by pipe are both read/write

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=210288

            Bug ID: 210288
           Summary: File descriptors created by pipe are both read/write
           Product: Base System
           Version: 11.0-CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: kwilliams at qnx.com

Created attachment 171448
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=171448&action=edit
test program demonstrating the issue

pipe(2) is documented by as returning 2 file descriptors, one for reading the
other for writing. 

"Data can be written to the file descriptor fildes[1] and read from the file
descriptor fildes[0]. A read on the file descriptor fildes[0] shall access data
written to the file descriptor fildes[1] on a first-in-first-out basis."

The actual implementation ends up wiring fd[0] to fd[1] such that writes on
fd[1] provide data that can be read on fd[0] (as required). Oddly writes to
fd[0] provide data that can be read in fd[1].

This deviates from the Posix spec (or at least stomps fully into the 'grey'
area), resulting in FBSD utilities being rendered portable between unix-like
distros.

The attached test program demonstrates this behavior. On strictly compliant
distros the attached code will result in the child write and parent read
failing.

-- 
You are receiving this mail because:
You are the assignee for the bug.