bash usage of fdescfs [was: Re: amd64/188699: Dev tree]

[Konstantin Belousov]

On Mon, Apr 21, 2014 at 05:23:04PM -0400, John Baldwin wrote:
> On Monday, April 21, 2014 3:51:33 pm Konstantin Belousov wrote:
> > On Mon, Apr 21, 2014 at 02:31:12PM -0400, John Baldwin wrote:
> > > On Thursday, April 17, 2014 2:50:01 pm Konstantin Belousov wrote:
> > > > The following reply was made to PR amd64/188699; it has been noted by 
> GNATS.
> > > > 
> > > > From: Konstantin Belousov <kostikbel at gmail.com>
> > > > To: John Allman <freebsd at hugme.org>
> > > > Cc: freebsd-gnats-submit at FreeBSD.org
> > > > Subject: Re: amd64/188699: Dev tree
> > > > Date: Thu, 17 Apr 2014 21:44:52 +0300
> > > > 
> > > >  On Wed, Apr 16, 2014 at 05:32:45PM +0000, John Allman wrote:
> > > >  > This is how to reproduce it:
> > > >  > 
> > > >  > Fresh install of 10 on AMD 64
> > > >  > install bash `pkg install bash`
> > > >  > Switch to bash `bash`
> > > >  > push a here document into a loop: `while true ; do echo; done< <(echo 
> "123")`
> > > >  > receive an error: "-su: /dev/fd/62: No such file or directory"
> > > >  > 
> > > >  > I'm sorry I haven't been able to research this any further. I found 
> how while working on some important matters. As I mentioned the above works 
> fine in all 
> > > previous versions of FreeBSD up until 10.
> > > >  > >How-To-Repeat:
> > > >  > Fresh install
> > > >  > pkg install bash
> > > >  > bash
> > > >  > while true; do echo foo done< <(echo "123")
> > > >  > 
> > > >  > -su: /dev/fd/62: No such file or directory
> > > >  
> > > >  So do you have fdescfs mounted on /dev/fd on the machine where the
> > > >  test fails ?  It works for me on head, and if unmounted, I get the
> > > >  same failure message as yours.  I very much doubt that it has anything
> > > >  to do with a system version.
> > > 
> > > Question I have is why is bash deciding to use /dev/fd/<n> and require
> > > fdescfs?  On older releases bash uses named pipes for this instead.
> > 
> > The aclocal.m4 contains the test which verifies the presence and usability
> > of /dev/fd/n for n>=3 on the _build_ host.  The result of the test
> > is used on the installation host afterward.
> > 
> > Such kinds of bugs are endemic in our ports, but apparently upstreams
> > are guilty too.
> 
> Yuck, yuck.  Should we fix our default package builders to not mount fdescfs?

IMO, using /dev/fd is more efficient since it avoids pipe inode creation
for the 'document here' interpretation.  The /dev/fd is also needed for
fexecve(2) to work (with the shebang scripts).  Also, I believe that
some other high-profile ports require it (OpenJDK ?).

That said, the solution is to have fdescfs mounted on /dev/fd.
This probably should be done by an installer.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 834 bytes
Desc: not available
URL: <http://lists.freebsd.org/pipermail/freebsd-ports/attachments/20140422/350aa97d/attachment.sig>