misc/77493: freebsd 5.3 + bash process substitution

[Bruce Evans]

The following reply was made to PR kern/77493; it has been noted by GNATS.

From: Bruce Evans <bde at zeta.org.au>
To: Travis Morgan <travis at bigfiber.net>
Cc: freebsd-gnats-submit at freebsd.org
Subject: Re: misc/77493: freebsd 5.3 + bash process substitution
Date: Thu, 24 Mar 2005 21:06:23 +1100 (EST)

 On Wed, 23 Mar 2005, Travis Morgan wrote:
 
 > I filed this bug with the bash bugs team as well and received the following response from them. According to Chet this would appear to be a FreeBSD problem, not a bash problem.
 
 > Date: Wed, 9 Mar 2005 21:45:17 -0500
 > From: Chet Ramey <chet at caleb.ins.cwru.edu>
 > ...
 > I think this is a FreeBSD bug.  I did some testing today using
 > 5.4-PRERELEASE.
 >
 > The bash `read' builtin, unless it's reading from a pipe, uses
 > buffered reads.  When reading from stdin, upon reading a newline, it
 > must seek the input file pointer back to the offset of the newline to
 > avoid potentially stealing input from other programs.
 >
 > This seeking backward does not work when applied to named pipes on
 > FreeBSD 5.[34], though there is no indication that it fails.
 >
 > I don't know how FreeBSD implements named pipes, but they're not pipes:
 > lseek doesn't return failure when applied to them.
 > ...
 
 This (the non-failure of lseek() on named pipes) was fixed in 1996 in
 rev.1.52 of vfs_syscalls.c and associated changes, but was broken in
 2003 in rev.1.319 of vfs_syscalls.c and associated changes.  See PR
 65786 for details.  (This PR is about the affect of lseek()'s bug on
 dd.)
 
 Bruce