Re: [PATCH 2/3] t5615: avoid re-using descriptor 4

> On Thu, Oct 19, 2017 at 07:23:37PM -0400, Jeff King wrote:
>
>> So one trick is that we can't just set it to a higher number. We have to
>> also open and manage that descriptor. It might be enough to do:
>>
>>   if test -n "$BASH_VERSION"
>>   then
>>       exec 999>&4
>>       BASH_XTRACEFD=999
>>   fi
>> [...]
>> I think it might be workable, but I'm worried we're opening a can of
>> worms. Or continuing to dig into the can of worms from the original
>> BASH_XTRACEFD, if you prefer. :)
>
> So this is the best I came up with (on top of my other patches for
> ease of reading, though I'd re-work them if this is the route we're
> going to go):
>
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 14fac6d6f2..833ceaefd2 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -377,7 +377,12 @@ fi
>  #
>  # Note also that we don't need or want to export it. The tracing is local to
>  # this shell, and we would not want to influence any shells we exec.
> -BASH_XTRACEFD=4
> +if test -n "$BASH_VERSION"
> +then
> +       exec 999>&4
> +       BASH_XTRACEFD=999
> +       silence_trace="999>/dev/null"
> +fi
>
>  test_failure=0
>  test_count=0
> @@ -627,14 +632,16 @@ test_eval_ () {
>         #     be _inside_ the block to avoid polluting the "set -x" output
>         #
>
> -       test_eval_inner_ "$@" </dev/null >&3 2>&4
> -       {
> -               test_eval_ret_=$?
> -               if want_trace
> -               then
> -                       set +x
> -               fi
> -       } 2>/dev/null 4>&2
> +       eval '
> +               test_eval_inner_ "$@" </dev/null >&3 2>&4
> +               {
> +                       test_eval_ret_=$?
> +                       if want_trace
> +                       then
> +                               set +x
> +                       fi
> +               } 2>/dev/null '"$silence_trace"'
> +       '
>
>         if test "$test_eval_ret_" != 0 && want_trace
>         then
>
> I really hate that extra eval, since it adds an extra layer of "+" to
> the tracing output in bash.