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Re: Risky local variable mechanism


From: Stefan Monnier
Subject: Re: Risky local variable mechanism
Date: Wed, 08 Feb 2006 00:07:45 -0500
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux)

>> Even for the list of safe vars, there's a significant problem: future
>> Emacsen may change (typically extend) the possible values of a var and/or
>> their meaning, so that a safe var may become unsafe.
>> 
>> I think we should only use `safe-variable' symbol-properties (only expected
>> to be set by maintainers, and which can be removed/refined if necessary) and
>> then for each var, an additional list of values which are considered safe
>> (this can be set by users, or even automatically set when the user answers
>> the interactive question).

> I don't see how this would help.  As long as it is possible for a user
> to explicitly set a variable as safe, there will be some sort of risk
> of this sort.  (For example, regarding your idea, I could put on my
> "anal retentive" hat and argue that previously safe values could turn
> into unsafe ones in future Emacsen ;-)

The probability of a safe value becoming dangerous is much lower.  Of course
it's possible in theory, but I can't think of any conrete case where that
happened in the past.

> Generally, I'm dubious about introducing any sort of complexity into the
> local variables system, since, in practice, one only encounters a rather
> small set of local variables which are generally obviously safe.

Several people would like to be able to specify extra font-lock keywords,
but font-lock-keywords include parts that are passed to `eval'.

>> BTW, maybe the interactive question should allow more than 2 answers:
>> - refuse those local variable settings this time.
>> - refuse them now and every time in the future.
>> - (maybe) refuse them in this Emacs session.
>> - accept them but just this one time.
>> - accept them every time.
>> - (maybe) accept them just for this Emacs session.
>> This way, there's still only one prompt.

> I also thought of this, but couldn't find a good way to fit multiple
> choices onto a single prompt.  Is there an example of this kind of
> prompt elsewhere in Emacs?

How 'bout the query/replace prompt?


        Stefan




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