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

Subject: Re: [boost] questions regarding dependency reports(s)
From: John Maddock (boost.regex_at_[hidden])
Date: 2014-09-27 04:36:38

> 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?

bcp will do that now with the --scan option, for example:

bcp --list --scan myfile.cpp

Will list the dependent headers and source files of myfile.cpp.

However, note that:

* It finds too much - broken compiler workarounds pull in additional 
includes you may not need on *your* compiler - this is the most common 
complaint - but of course without this the subset isn't actually 
portable.  I suspect (with no data to back it up!) that this issue may 
reduce as we increasingly support only newer compilers.
* It finds too much (part 2) - if it finds a header from library X, and 
library X has some source files associated with it, then those files and 
their dependencies get included.  Of course there are some libraries 
that have "optional" source files - only required if you use some 
specific header subset.
* It finds too little - it can't follow obfuscated includes (via 
preprocessor defs) - though neither can other dependency scanning tools 
as far as I know.  There is a mechanism inside bcp to add specific 
manual dependencies when required, but as you can imagine, it's always 
out of date.

One point worth noting - bcp is not an offline installer - it can only 
scan what's on your hard drive.  I guess though it could be used to 
produce an install list for each library with each release - that would 
get us into an endless debate about what such a list should include:

1) Dependencies required to use the library.
2) What about optional dependencies / from bridging/glue headers?
3) What about dependencies required by examples/tests?

I guess that (2) and (3) could be made separate packages?

John.