default-directory safe file local variable but no check for same if file-exists-p

default-directory safe file local variable but no check for same if file-exists-p

[MON KEY]

`default-directory' can be marked a safe file local variable if it
satisfies the stringp predicate.
Does this not allow failure in unsafe ways when (not file-exists-p) is
non-nil for same?
- what gives?

s_P

Re: default-directory safe file local variable but no check for same if file-exists-p

[Stefan Monnier]

> Does this not allow failure in unsafe ways when (not file-exists-p) is
> non-nil for same?

It shouldn't.  Even under normal circumstances, default-directory may
point to a non-existing directory (e.g. because it existed when the
buffer was created, but has been removed in the mean time).


        Stefan

Re: default-directory safe file local variable but no check for same if file-exists-p

[MON KEY]

On Fri, Jun 5, 2009 at 10:31 AM, Stefan Monnier<monnier@iro.umontreal.ca> wrote:
> It shouldn't.  Even under normal circumstances, default-directory may
> point to a non-existing directory (e.g. because it existed when the
> buffer was created, but has been removed in the mean time).

Ok. Thank you. That makes sense.

I'm sure this is all very well thought out, and I apologize if this
comes across as foolish, but out of curiosity does this account for
procedures such as `process-file', `call-process', `start-process',
`start-file-process' etc. which base their file-handlers on the
`default-directory' value?

e.g. the default-directory doesn't exist at buffer creation, a
sub-process (synchronous or otherwise) comes along, attempts to take
residence in default directory, and not finding a 'there' there,
proceeds to build himself a new home.

s_P

Re: default-directory safe file local variable but no check for same if file-exists-p

[Davis Herring]

> I'm sure this is all very well thought out, and I apologize if this
> comes across as foolish, but out of curiosity does this account for
> procedures such as `process-file', `call-process', `start-process',
> `start-file-process' etc. which base their file-handlers on the
> `default-directory' value?

My thought on this subject is that values of `default-directory' that
involve Tramp might be a problem, although I'm not sure how to exploit
being able to have someone SSH somewhere or become root on their own
machine.

Davis

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