Re: Gtk+ print support - request for feedback

[Michael Sweet <mike easysw com>]

Alexander Larsson wrote:
> On Fri, 2006-03-03 at 13:59 -0500, Morten Welinder wrote:
> > What's the status of thread safety?  Last I looked at cups it was
> > not thread safe due to calling setlocale, and there was little
> > understanding as to why that was a problem.
> >
> > (And recall that just about any gtk+ program is at least
> > minimally threaded.)
>
> Hmm, cups still seems to be changing the locale. Both for parsing floats
> in the ppd with "." as separator, and in cupsLangGet() (where it calls
> setlocale(LC_ALL, NULL) if the locale wasn't already set).

The "setlocale(LC_ALL, NULL)" call is safe - it returns the current
value.  The only time we set the locale is when the user calls
cupsLangDefault() and hasn't already called setlocale()...

We *do* currently save/restore the LC_CTYPE locale settings right now,
but I *think* that part can be removed now (will check) since we've
changed how the message catalogs are loaded.

> We can avoid calling anything that results in cupsLangGet(), but not the
> float parsing. 
>
> Michael, is there any chance that this will be fixed in cups? The way
> gtk+ does threadsafe locale-independent float parsing is this: 
> (I wrote this code, so if you want to use it in cups I'm ok with
> re-licensing it in a suitable way)

I'd rather avoid introducing a hack like this if we can avoid it.
Also, we use sscanf() in the PPD code to parse multiple float values,
so it will be necessary to do something a little more invasive in our
code... :(

The man page for setlocale() says nothing about thread safety, but
given how all of the other standard C calls work I'm frankly shocked
that setting the locale in one thread affects the others.  Is this
just a bug on Linux, or is it a general problem on other operating
systems?

--
______________________________________________________________________
Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Publishing Software        http://www.easysw.com