Strange behavior of $jobstates

Strange behavior of $jobstates

[Manabu Matsui]

I found a strange behavior of $jobstates. When I pipe the output of
echo $ jobstates,
its output is empty. This has occurred for zsh 5.6.2 (x86_64-apple-darwin18.0.0)
installed on my mac with homebrew.

% sleep 30
sleep 30
^Z
zsh: suspended  sleep 30
% echo $jobstates
suspended:+:16815=suspended
% echo $jobstates | cat

% echo $jobstates
suspended:+:16815=suspended

This does not occur for zsh 5.4.2 (x86_64-ubuntu-linux-gnu) on ubuntu.

Re: Strange behavior of $jobstates

[dana]

On 12 Nov 2018, at 22:46, Manabu Matsui <manabu.matsui@gmail.com> wrote:
>I found a strange behavior of $jobstates. When I pipe the output of
>echo $ jobstates,
>its output is empty.

The difference is the result of faf0035e53 (workers/42702). I guess anything
that previously used information from the current (soon-to-be-parent) shell,
like $jobstates and $sysparams[pid], would be affected that way. Seems
consistent with how the change was described, but i'm not sure

dana

Re: Strange behavior of $jobstates

[Manabu Matsui]

On 13 Nov 2018, at 16:53, dana <dana@dana.is> wrote:
> The difference is the result of faf0035e53 (workers/42702). I guess anything
> that previously used information from the current (soon-to-be-parent) shell,
> like $jobstates and $sysparams[pid], would be affected that way. Seems
> consistent with how the change was described, but i'm not sure

Thank you for your answer.

Does this mean that the parameter expansion processing is changed from
the parent process before fork to the child process after fork?

As a result of this change, the operation of the parameter expansion
having a side effect also has changed. Is this intended?

Before this change (zsh 5.4.2 (x86_64-ubuntu-linux-gnu)):
% a=1
% echo ${a::=2}|cat
2
% echo $a
2

After this change (zsh 5.6.2 (x86_64-apple-darwin18.0.0)):
% a=1
% echo ${a::=2}|cat
2
% echo $a
1

Re: Strange behavior of $jobstates

[Peter Stephenson]

On Wed, 2018-11-14 at 10:43 +0900, Manabu Matsui wrote:
> As a result of this change, the operation of the parameter expansion
> having a side effect also has changed. Is this intended?
> 
> Before this change (zsh 5.4.2 (x86_64-ubuntu-linux-gnu)):
> % a=1
> % echo ${a::=2}|cat
> 2
> % echo $a
> 2
> 
> After this change (zsh 5.6.2 (x86_64-apple-darwin18.0.0)):
> % a=1
> % echo ${a::=2}|cat
> 2
> % echo $a
> 1

Yes, the change is correct.  Setting a parameter in the left hand side
of the pipeline shouild not affect anything outside the pipeline.

Although the standard doesn't specify which side of the pipeline is run
in a forked copy, in zsh it's always the left hand side, so the fact
that effects were escaping from there was a bug.

pws

Re: Strange behavior of $jobstates

[Manabu Matsui]

On Wed, 14 Nov 2018 09:27:15 +0000, Peter Stephenson
<p.stephenson@samsung.com> wrote:

> Yes, the change is correct.  Setting a parameter in the left hand side
> of the pipeline shouild not affect anything outside the pipeline.
>
> Although the standard doesn't specify which side of the pipeline is run
> in a forked copy, in zsh it's always the left hand side, so the fact
> that effects were escaping from there was a bug.

I

Thank you for the easy-to-understand explanation. t was difficult for
me to understand with ChangeLog description alone.