Re: Zsh 4.3.12: subshell in midnight commander: precmd: 15: bad file descriptor

[Peter Stephenson <Peter.Stephenson@csr.com>]

On Mon, 18 Jul 2011 08:52:34 -0700
Bart Schaefer <schaefer@brasslantern.com> wrote:
> Hrm.  So why does it work when starting 4.3.12 from 4.3.9?  How is 11
> getting to be <= max_zsh_fd inside 4.3.12 that case, whereas it is not
> when the outer shell is 4.3.12?

See what lsof says.  I suspect 4.3.9 is leaving open its SHTTY, since
setting FD_CLOEXEC on that is one of the changes I noted.  That would be
fd 12, so 11 is <max_zsh_fd.

> It prevents the specific error in question, but there are also going to be
> changes needed here:
> 
>    2975                         fn->fd1 = (int)getintvalue(v);
>    2976                         if (errflag)
>    2977                             bad = 1;
> *  2978                         else if (fn->fd1 > max_zsh_fd)
>    2979                             bad = 3;
>    2980                         else if (fn->fd1 >= 10 &&
>    2981                                  fdtable[fn->fd1] == FDT_INTERNAL)
>    2982                             bad = 4;

Hmm... that's saying we're closing an fd with {foo}>&- syntax that
we don't know about in the first place.  Do we just try to close it and
report an error closing an unknown fd if that fails?

> And what's going to happen when max_zsh_fd does in fact become greater
> than the "unknown" descriptor?  Any problems with fdtable[x] having
> bogus data?  Isn't closem() going to attempt to close a descriptor
> that it shouldn't?

I think that works, since we handle unknown fd's marked as unknown as
best we can.  In fact, I think you may just have tested it.

-- 
Peter Stephenson <pws@csr.com>            Software Engineer
Tel: +44 (0)1223 692070                   Cambridge Silicon Radio Limited
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