[cxml-devel] Handling doctype declarations for system-ids?

[Marco Antoniotti]

On Mar 20, 2006, at 5:29 PM, David Lichteblau wrote:

> Quoting Marco Antoniotti (marcoxa at cs.nyu.edu):
>> Just to be nitpicking.  Merging *d-p-d* (which I assume to be
>> *DEFAULT-PATHNAME-DEFAULTS*) isn't guaranteed to work.  *d-p-d* can be
>> a relative pathname.  Wouldn't that cause the same problem?
>
> Well, ISTR that CMUCL starts with an empty *default-pathname-defaults*,
> so I recognize that CMUCL users might indeed still have this problem
> even with the patch.
>
> And since the spec is terribly vague on this issue (like most issues
> relating to pathnames), the implementation choice made by CMUCL
> maintainers is technically correct.
>
> However,
>   - the spec does say that *default-pathname-defaults* is "typically in
>     the working directory that was current when Common Lisp was 
> started up".
>   - it's the only approximation of the concept of a "working directory"
>     I am aware of in portable Common Lisp and many Lisps implement it
>     like that.
>   - if the implementation chooses not to set it to the working
>     directory, users can easily fix that by setting or binding it
>     themselves.  (Or, of course, by passing an absolute pathname to
>     cxml:parse-file in the first place...)
>
> So using it seems like a reasonable compromise to me, and improves the
> situation on some Lisps while not making it worse on the others.

I do think that it still has problems.  Think of

(let ((*default-pathname-defaults* (make-fiendshly-relative-pathname)))
    ;; run CXML code.
)

It is true that *d-p-d* is usually what you think, but since it is a 
variable that can be manipulated, it is not safe to assume any value 
for it.

I would either introduce a CXML variable, or use USER-HOMEDIR-PATHNAME, 
which is guaranteed to be "constant".

In alternative, I would use some package that masks the implementation 
vagaries and gives you the notion of "working directory".  CLOCC port 
is one of them (or, shameless plug, cl-environment)

Cheers

Marco
--
Marco Antoniotti					http://bioinformatics.nyu.edu/~marcoxa
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