Re: What's the right way to detect libxml2?

[Phillip Lord]

On Sun, October 22, 2017 2:14 pm, Clément Pit-Claudel wrote:
> Hi emacs-devel,
>
>
> In Flycheck we use ``libxml-parse-region`` if available, and fall back to
> ``xml-parse-region`` otherwise.  We recently realized that our libxml
> detection code was wrong, however.
>
> We used to write ``(if (fboundp 'libxml-parse-region)
> (libxml-parse-region …) (xml-parse-region …))``, but this isn't
> sufficient on Windows, where ``fboundp`` succeeds if Emacs was compiled
> with libxml support, even if the appropriate DLL isn't installed on the
> user's system.
>
> What's the proper way to autodetect libxml? We're thinking of doing this
> instead::
>
>
> (if (and (fboundp 'libxml-parse-region)
> (with-temp-buffer
> (insert "<xml/>")
> (libxml-parse-region (point-min) (point-max))))
> (libxml-parse-region …)
> (xml-parse-region …))
>
>
> Do we have better options?

We need a better option, as it happens. I have the same problem when
building the windows binary package. I've got no way of testing whether
libxml (or any of the other DLLs) are present or work.

Phil