Subject: bug#8846: coreutils-8.12 on HP-UX 11.31: 3 of 365 tests failed

From: Eric Blake <[email-masked]>
Date: Mon, 13 Jun 2011 16:05:27 -0600

On 06/13/2011 03:39 PM, Stefano Lattarini wrote:
> 
>  [3] The $(SHELL), which here we assume is ksh with close-on-exec, does a
>      fork+exec to execute the test script; thus, when that script begins
>      its execution, it has the fd 9 closed (d'oh!, but expected now);

Oddly enough, it looks like it is _only_ 'exec 9>&2' that suffers from
close-on-exec semantics; using '(blah) 9>&2' leaves fd 9 inheritable.

So maybe the real fix is to do the redirection to a subshell or grouping
{} rather than via exec, at which point even ksh and HP-UX sh will allow
the original stderr to be inherited as fd 9 to the child script process:

$ printf '#!/bin/sh\nexec >&9\n' > k
$ sh k
k[2]: 9: Generated or received a file descriptor number that is not valid.
$ sh k 9>&2
$ sh -c 'exec 9>&2; /bin/sh k'
k[2]: 9: Generated or received a file descriptor number that is not valid.
$ sh -c 'sh k 9>&2'
$ sh -c '(sh k) 9>&2'
$ sh -c '{ sh k;} 9>&2'
$

but I don't know if that will require some changes in automake's
parallel-test driver setup code.

And Autoconf should probably document that the close-on-exec semantics
of some shells applies only to the exec builtin, since they do not
happen to other redirections.

-- 
Eric Blake   [email-masked]    +1-801-349-2682
Libvirt virtualization library http://libvirt.org