Re: [Boost-build] Improving development (edit, build, debug) cycle times

From: Johan Nilsson (r.johan.nilsson_at_[hidden])
Date: 2008-02-15 05:31:31

K. Noel Belcourt wrote:
> Hi,
>
> In our projects, we find the bjam startup time (the time for the
> first build action to run) can be very lengthy (anywhere from 2-6
> minutes or more, on fast hardware with all source files located on
> local disks).  This is entirely due to the size of our projects, the
> large numbers of files involved, and we accept this.  But one of our
> more common development use cases occurs where a developer repeatedly
> edits the same small number of files, then builds and debugs their
> changes, and then repeats the cycle.  In this development model, the
> developer isn't altering any dependencies so the exact same set of
> files are compiled and linked each time, with no changes to include
> or library paths, or anything.

I've brought up the subject in this mailing list some time ago (but can't 
find the actual posts in the archive). IIRC, what I was asking for was the 
ability to limit the header scanning to e.g. the "immediate" include 
directories.

I also seem to remember some discussion about the more complex scenario of 
having a dedicated "bjam daemon" running in the background and continously 
updating the dependency information for certain projects.

>
> Because the bjam startup time can be very long and the dependencies
> are not changing, I believe it would be useful to add the ability for
> bjam to write out the build actions to a file that our developers
> could then execute (e.g. as a shell script) to dramatically shorten
> their development cycle times.

I'd prefer an additional switch to bjam if possible, e.g. 
"bjam --no-external-deps" (or perhaps "bjam --fast-and-unsafe").

>
> Would this capability be useful to the community?

Yes, definitely (especially for us test-first programmers)!

/ Johan