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Re: [PATCH] document shell function problems


From: Eric Blake
Subject: Re: [PATCH] document shell function problems
Date: Fri, 05 Oct 2007 13:25:18 -0600
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According to Paolo Bonzini on 10/5/2007 3:17 AM:
> Here is what I could gather from reports on address@hidden In
> particular http://www.mail-archive.com/address@hidden/msg15966.html
> suggested me the following minimal reproducer
> 
>   test -n "${ZSH_VERSION+set}" && emulate sh
>   failure1 () {
>     (exit 1)
>     echo $?
>   }

Should we add this into m4sh's _AS_DETECT_SUGGESTED_BODY, to skip zsh when
something better is present?

> +You should not use aliases, negated character classes, or other features
> +that are not found in all Bourne-compatible shells; restrict yourself
> +to the lowest common denominator.  Even @code{unset} is not supported
> +by all shells!

Is unset supported by all shells that also support functions?  That would
be a nice simplification to rely on.

> +
> +Shell functions are considered portable nowadays, though Autoconf
> +still does not use them (Autotest does).  However, inside a shell
> +function you should not be using @code{$?} to check the return code
> +of a subshell invocation; in general, since the caller of a shell
> +function might look at the function's return code, make sure that the
> +last statement of a shell function does not invoke a subshell.
> +Using subshells triggers bugs in zsh 4.x; while Autoconf tries
> +to find a shell that does not exhibit the bug, zsh might be the
> +only shell present on the user's machine.
> 

Looks good, please apply.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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