PATCH: Re: PATCH: local exports

[Peter Stephenson <pws@cambridgesiliconradio.com>]

Bart Schaefer wrote:
> The following seems to be a pretty effective test:
> 
>   unenv() {
>     local x
>     x=($(typeset +x))
>     local $x
>     unset $x
>     /usr/bin/printenv	# $path is (correctly?) nuked by unset PATH
>   }
> 
> The output on my system differs if I run this function twice.  The first
> time it is:
> 
>   TERM=xterm
>   HOME=/home/schaefer
>   _=/usr/bin/printenv
>   COLUMNS=80
>   LINES=24

Oddly, this wasn't actually my fault; it came from the import of special
parameters at startup.  The code set the variable, then tried to replace
the value in the environment with the value generated internlly, for
consistency.  Unfortunately it was trying to replace it into the old
environment, which failed.  This returned null, which was set to the env
element of the parameter struct.  Hence when the new code looked for this
to see if the value was in the environment already it failed, so never
deleted it.  (It was doing this on the `local', not the unset, since the
local parameter wasn't being exported.)  This usually didn't show up
because the values in the environment were OK anyway, as in this case, so
the fact that they didn't get replaced didn't matter.

> } This was necessary to get around the -g-with--x kludge.  Ksh 88 doesn't
> } have that and its `typeset -x' behaves more or less like `typeset +g -x'.
> 
> This is why I keep talking about ksh emulation.  I want to be able to
> keep exporting things from functions with `typeset -x' the way I have
> for the entire time I've been using zsh, but it causes problems when
> running scripts written for ksh.

OK, so it's a ksh compatibility vs. old zsh compatibility issue.  The
problem with using an option is that in this case the latter is the kludge,
but needs to be enabled by default.  There isn't a good way round that.
If somebody wants to write an option they can.  It could be called e.g.
GLOBAL_EXPORT and be on by default; at least that tells you that something's
up.

Index: Src/params.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/params.c,v
retrieving revision 1.4
diff -u -r1.4 params.c
--- Src/params.c	2000/04/13 14:22:47	1.4
+++ Src/params.c	2000/04/13 17:51:26
@@ -454,6 +454,7 @@
 {
     Param ip, pm;
     char **new_environ, **envp, **envp2, **sigptr, **t;
+    char **old_environ = environ;
     char buf[50], *str, *iname;
     int num_env, oae = opts[ALLEXPORT];
 #ifdef HAVE_UNAME
@@ -516,9 +517,12 @@
 		    pm->flags |= PM_EXPORTED;
 		    pm->env = *envp++ = ztrdup(*envp2);
 		    *envp = NULL;
-		    if (pm->flags & PM_SPECIAL)
+		    if (pm->flags & PM_SPECIAL) {
+			environ = new_environ;
 			pm->env = replenv(pm->env, getsparam(pm->nam),
 					  pm->flags);
+			environ = old_environ;
+		    }
 		}
 	    }
 	    *str = '=';

-- 
Peter Stephenson <pws@cambridgesiliconradio.com>
Cambridge Silicon Radio, Unit 300, Science Park, Milton Road,
Cambridge, CB4 0XL, UK                          Tel: +44 (0)1223 392070