EXIT trap and the return status

EXIT trap and the return status

[Oliver Kiddle]

I was trying to work out why the _prefix completer that follows
_approximate at the end of my completers is never being run in zsh 4.1.
The trace looks like this:

+_approximate:113> return 1
+_main_complete:1> unfunction compadd
+_main_complete:156> ret=0 
+_main_complete:157> break 2

The `unfunction compadd' comes from _approximate doing
  trap 'unfunction compadd' EXIT INT
The problem is that because that trap is successful, _approximate is
returning 0 instead of 1. This possibly has something to do with the
change in 17250. It doesn't seem right to me (and is inconsistent with
ksh93). So is this a bug? If not, I'll adjust _approximate.

Oliver

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Re: EXIT trap and the return status

[Peter Stephenson]

Oliver Kiddle wrote:
> I was trying to work out why the _prefix completer that follows
> _approximate at the end of my completers is never being run in zsh 4.1.
> The trace looks like this:
> 
> +_approximate:113> return 1
> +_main_complete:1> unfunction compadd
> +_main_complete:156> ret=0 
> +_main_complete:157> break 2
> 
> The `unfunction compadd' comes from _approximate doing
>   trap 'unfunction compadd' EXIT INT
> The problem is that because that trap is successful, _approximate is
> returning 0 instead of 1. This possibly has something to do with the
> change in 17250. It doesn't seem right to me (and is inconsistent with
> ksh93). So is this a bug? If not, I'll adjust _approximate.

No, executing a trap shouldn't change the return from the function ---
except in the case (not applicable here) of a TRAPNAL function, where
the return value of that function is used to decide whether the shell
should consider the signal has been handled or should return from the
function where the signal occurred as if the signal had been received
without a trap.  Probably that shouldn't apply to TRAPEXIT anyway.

It looks like it probably is an effect of 17250: I think the problem is
that the status value (lastval) at this point is expected to store the return
value from the function we are exiting from (which we want the trap to
leave alone), but if we do something clever like provoke the enclosing
function to exit, it can store the return value for that (which we want
to propagate).  Perhaps there's an obvious answer but I can't see it at
the moment.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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