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From: Bart Schaefer <schaefer@brasslantern.com>
Message-Id: <151006083446.ZM5523@torch.brasslantern.com>
Date: Tue, 6 Oct 2015 08:34:46 -0700
In-Reply-To: <20151006101549.3664bab3@pwslap01u.europe.root.pri>
Comments: In reply to Peter Stephenson <p.stephenson@samsung.com>
        "Re: syntax check of 'echo $HOME' crashes in ksh emulation mode" (Oct  6, 10:15am)
References: <1693579.IilOBOKrgc@kdudka.brq.redhat.com> 
	<20151005174219.69ae85c4@pwslap01u.europe.root.pri> 
	<151005104507.ZM19176@torch.brasslantern.com> 
	<20151006093357.0c7a5214@pwslap01u.europe.root.pri> 
	<20151006101549.3664bab3@pwslap01u.europe.root.pri>
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To: zsh-workers@zsh.org
Subject: Re: syntax check of 'echo $HOME' crashes in ksh emulation mode
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On Oct 6, 10:15am, Peter Stephenson wrote:
}
} /**/
} mod_export void
} assignstrvalue(Value v, char *val, int flags)
} {
}     if (unset(EXECOPT))
} 	return;
} 
} (i) Doesn't that leak val?

Probably, but in no_exec state the shell can't possibly run for very long
so it doesn't matter?  However, every other case in assignstrvalue() has
zsfree(val) so this one probably should too.  Except:

} (ii) It's not clear how safe the above is, as this case shows.  However,
} it's definitely not safe to skip the tests in assignstrvalue() either

Do you mean that even for no_exec we should not be bailing out this
early in assignstrvalue()?  That is, we ought to be doing the tests of
read-only, wrong type, invalid subscript, etc., and then bail just
before removing the PM_UNSET flag?  Except:

} and if we run them it's doing too much work for syntax checking and is
} likely to mess things up owing to previous non-execution.

I don't know about too much work, but yes, some of them proceed a bit
too far into semantics.

} So this is all a bit nasty.  (Just for once.)

Does POSIX say anything about the environment in no_exec state?  Maybe
we should just temporarily toggle EXECOPT off during that part of the
shell initialization -- we're already avoiding execution of contents
of environment vars for security reasons, so it should be safe to do
the imports.