[Ardour-Users] A4.4: Critical bug using calf's lv2

Paul Davis paul at linuxaudiosystems.com
Tue Oct 27 08:56:38 PDT 2015

On Tue, Oct 27, 2015 at 11:46 AM, Damien Delpiroux <xzurukneg at free.fr>

> Le 27/10/2015 16:03, Paul Davis a écrit :
> > CALF plugins have always been deeply problematic.
> I ear.
> But personally I never had any problem after hundreds hours of use, even
> with firsts versions of A4.

The problems are not deterministic.

There are specific known problems, most notably with the use of a
non-thread safe version of libfftw. This has been fixed in CALF git, but
has not been picked up by most distributions so far. We have also attempted
to fix this by shipping a thread-safe version of libfftw with recent builds
of Ardour itself. This particular bug can cause crashes as different
instances of a CALF (or other libfftw-using) plugin run on different CPUs,
and they overwrite data used by libfftw.

There are other issues with CALF that are more obscure. The situation is
definitely improving, but as a single plugin collection they have been by
far the most problematic.

There are other examples of this sort of "deep, non-deterministic" issue
with other plugins. There is an SWH ladspa plugin for example that can
randomly overwrite data in the channels of OTHER TRACKS!

We're not telling anyone to stop using CALF. We're not telling anyone to
stop using plugins (though I'd love to be able to). But if you use them,
you need to be aware of the potential risks. Loading arbitrary 3rd party
code into a big, complex program and then just hoping it all works ...
well, yeah. Good luck with that.
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