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

[Stefano Lattarini]

On Tuesday 14 June 2011, Eric Blake wrote:
> 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'
>
If this work, then using a bare `>&2' *at the end of TESTS_ENVIRONMENT* and
*without a following semicolon* might give a portable workaround, as if I'm
not mistaken POSIX mandates that redirections can be specified anywere on
the command line, and are to be evaluated from left to right.

UPDATE: Yes, it seems to work.  I'll add a testcase to the 'maint' branch in
case you and Jim decide to go with this solution (and you can confirm that it
really works).

> $ 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.
>  

Regards,
  Stefano