trap for EXIT doesn't catch exit?

trap for EXIT doesn't catch exit?

[Michal Vitecek]

 greetings,

 in one of my zsh programs i'm creating a number of temporary files which
 should be removed when the program execution stops or an error occurs
 and i call 'exit'.

 however after having specified 'trap CleanUp EXIT' the clean-up
 function is not called when 'exit' inside a function is executed.

 an example program (test.sh):
 ----start----
    #!/bin/zsh

    function CleanUp()
    {
	rm -f tempfile
    } 

    function WillExit()
    {
	exit
    }


    trap CleanUp EXIT
    touch tempfile
    WillExit
 ----end----

 $ chmod +x test.sh
 $ ./test.sh
 $ ls tempfile
 tempfile
 $

 in my understanding the CleanUp() function should be called, evidently
 it's not. what's wrong here?
 
	thanks for your help,
-- 
			fuf


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Re: trap for EXIT doesn't catch exit?

[Peter Stephenson]

Michal Vitecek wrote:
>  in one of my zsh programs i'm creating a number of temporary files which
>  should be removed when the program execution stops or an error occurs
>  and i call 'exit'.
> 
>  however after having specified 'trap CleanUp EXIT' the clean-up
>  function is not called when 'exit' inside a function is executed.
>
>  an example program (test.sh):
>  ----start----
>     #!/bin/zsh
> 
>     function CleanUp()
>     {
> 	  rm -f tempfile
>     } 
> 
>     function WillExit()
>     {
> 	  exit
>     }
> 
> 
>     trap CleanUp EXIT
>     touch tempfile
>     WillExit
>  ----end----
> 
>  $ chmod +x test.sh
>  $ ./test.sh
>  $ ls tempfile
>  tempfile
>  $

Yes, that certainly looks like a bug.

What's happening is this: when you enter the function WillExit, it saves
the trap for exiting the shell and resets the trap, so that if you set a
trap for EXIT it applies on to the function, not the shell.  Usually it
would restore this when the function exits.  However, when you call `exit',
it simply exits the shell without exiting the function scope.  So it never
sees the trap EXIT set for exiting the shell.

Probably the correct thing to do here is to pop all the saved EXIT's off
the stack of saved traps, executing them one by one, to simulate exiting
the scope of each function in turn.  I'll wait to see if there are comments
before I do that (further discussion should probably go to zsh-workers).

A temporary workaround is to install `trap CleanUp Exit' inside WillExit.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 392070


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