Re: [boost] questions regarding dependency reports(s)

Subject: Re: [boost] questions regarding dependency reports(s)
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2014-09-26 19:10:57

On Friday 26 September 2014 15:35:54 Robert Ramey wrote:
> 
> What would it take to make a version of BCP which, given
> an arbitrary group of source files, returns a list of headers
> and *.cpp files which could be used to build the app?

The main problem with bcp and header-based dependency tracking in general is 
dealing with preprocessor tricks which affect the inclusion graph. The cases 
when a macro unfolds in the header name are not uncommon. Even more 
complicated are cases when #include directives are conditioned on some tests 
like compiler version or platform or macros defined in other headers.

You could collect dependencies that correspond to a particular environment 
(e.g. the one you're currently running) but that wouldn't be a portable 
distribution. I suppose, the more correct approach would be to build a 
superposition of all possible condition results and preprocess each header in 
every possible way, but that's beyond what a normal C++ preprocessor does and 
I doubt this would be practical.

I think the most feasible way to do it is to preprocess headers multiple times 
according to a number of pre-defined environment presets, each corresponding 
to a platform Boost supports. It will still work rather slow, and defining 
these presets would be a tough job, but at least this looks doable.