Re: [Boost-build] Is there any way to prevent Boost.Build fromrecursively scanning header files for #include directives?

Subject: Re: [Boost-build] Is there any way to prevent Boost.Build fromrecursively scanning header files for #include directives?
From: Vladimir Prus (vladimir_at_[hidden])
Date: 2009-04-29 08:59:36

J. van der Wulp wrote:

> I did not have a look at any of the scanning internals. From a naive
> look at some level 3 debug logs I got the impression that a lot of
> scanning work is being done more than once.
> 
> Is it possible to improve performance by caching scan results? It seems
> as though a lot of header files are scanned repeatedly. Or is this a
> consequence differences of preprocessor contexts that are taken into
> account by the scanner?
> 
> The Big Question: do bjam/Boost Build v2 developers think that there is
> room for performance improvement in this regard? Does any substantial
> performance improvement in scanning come at the expense of correctness?

Most of the time taken by scanning is time inside Boost.Build code. So, caching
the 'raw' scanning results does not give much performance advantage. Caching
at a higher level is considerably harder. My current opinion is that we should
get Python port to a state where it can build entire Boost C++ Libraries and
see what performance is in that case. It might be good enough to make any
further tweaking not necessary.

- Volodya