[pdal] Boost versioning

[Howard Butler]

On Feb 2, 2012, at 10:51 AM, Michael P. Gerlek wrote:

> Yesterday Mr. Rosen found yet another problem with Boost compatibility (1.47.x against VS2010)
> 
> This is a topic for the Sprint next week, but maybe we can jump start it here...

Near as I can tell, Boost's compatibility story is such a mess that projects simply give up and embed the version they need.  In fact there's tools to make that scenario easier.  Active projects like PCL, Mapnik, et. al seem to "use the latest release" at the developer level, and then expect that packagers take care of compilation issues

> 
> - We need to support whatever version the major linux distros are using

RHEL 6.1 is Boost 1.41, I believe.  I think Debian is about at that too.  It's too old for a lot of stuff.

> - We want to support the (relatively) latest-and-greatest release (so we get nifty stuff we can gratuitously splatter all over the codebase :-)

There's a couple of big discontinuities that affect us:

- Boost filesystem changed from 2 to 3, and the transition is painful and requires #ifdefs
- Boost random in 1.48 has some fancy stuff I'd like to use for pdal::filters::Stats
- Boost spirit, to be used for our expression parser, has had some changes in the 1.44-1.46 timeframe.

> Can we then cut this problem down to just supporting two versions?  Or are there other concerns?  (like, which boost do the Mac fanboys use?)

we quickly get to the point where it's easier to embed the things we want and not depend on getting screwed by the system boost...