Re: [boost] [build][wave][spirit] tools/wave link failure

From: Hartmut Kaiser (hartmut.kaiser_at_[hidden])
Date: 2008-01-31 17:36:40

Rene,

> >>> I'm not sure where the -lpthread needs to be added (I added it
> >> manually
> >>> to the link command and it succeeded), or in fact, why wave links
> to
> >>> boost_thread at all. It doesn't use threads underneath, or does it
> ?
> >> It turns out the dependency on boost_thread is dragged in by
> >> boost.spirit. (I modified the subject line to reflect this.)
> >>
> >> I'm not sure in what way boost_thread is used there, but I would
> hope
> >> that the decision to use threads (and boost_thread) could be left to
> >> the
> >> library's user. Only pay for what you really use, or so the saying
> >> goes...
> >>
> >> Is it possible to modify the config logic to have some users only
> use
> >> the subset of boost.spirit that doesn't require boost_thread ?
> >>
> >> (I'm writing a preprocessor and I do not want to use threads, so why
> >> would I have to link with boost_thread and pthread ?)
> >
> > Wave drags in threads only if it gets compiled in an environment
> requiring
> > threads (BOOST_HAS_THREADS is defined). If you build Wave such that
> > BOOST_HAS_THREADS is not defined, it won't depend on threads.
> 
> What happens when one wants to use Wave without threads in a platform
> that has threads?

Ok, I added a corresponding configuration option on the trunk. Before that
the Wave config looked just at the BOOST_HAS_THREADS macro. Here is the
corresponding new snippet from the wave_config.hpp file:

//  If BOOST_WAVE_SUPPORT_THREADING is not defined, Wave will use the global

//  Boost build settings (BOOST_HAS_THREADS), if it is defined its value
//  defines whether threading will be enabled or not (should be set to '0' 
//  or '1').

Does this help?

Should I add this to the 1.35 release branch as well? It shouldn't have any
influence on the Wave regression tests whatsoever.

> Also...
> 
> Is a thread safe Wave and Spirit (or Phoenix) that doesn't use Boost
> Threads available? I.e. are there reentrant versions available?

The Wave code itself is reentrant, but since it's using Spirit V1
underneath, which is not, the overall library isn't reentrant either.
Spirit V2 will be thread agnostic, i.e. the user decides and is responsible.

> By the way the reason Stefan and I are asking about this is that
> currently using a static version of Wave doesn't build on some
> platforms
> as Boost Threads needs extra user work to build statically.

Ok, understand.

Regards Hartmut