[build2] Generating source code in build2 projects

[Bruce Sutherland]

Thank you Boris, that's very helpful. I'll start out with ad hoc
recipes, and will reach out again if we run into trouble.

On Fri, Jul 31, 2020 at 1:42 PM Boris Kolpackov <boris at codesynthesis.com> wrote:
>
> Bruce Sutherland <bsutherland at soundhound.com> writes:
>
> > So I assume we need to configure blubc as a tool in build2, and define
> > dependencies from .blub to .cpp and .h files.
> >
> > How should we do that with build2? The documentation mentions
> > generated source code, but doesn't go into much detail. Can anyone
> > point me to an example of a project with a similar configuration?
>
> Currently there are two way to do this: you can provide a rule for
> compiling any .blub to .h/.cpp or you can provide an ad hoc recipe
> for compiling a specific foo.blub to foo.h/foo.cpp.
>
> To provide a rule, currently, you will have to write a build system
> module that implements it (see, for example, libbuild2-rust[1]). In
> the next release we are also planning to add support for ad hoc rules
> that can be written directly in buildfiles (similar to ad hoc recipes
> below).
>
> An ad hoc recipe you can write directly in the buildfile and I would
> suggest that you start with that since writing a rule/module is fairly
> involved. The release notes for 0.13.0[2] have a number of examples
> that should get you started (in particular, see the xxd example).
> There is also a NASM example[3] I posted a few days ago that shows
> how to define a custom target type (e.g., for .blub).
>
> Note also that this is still an area of active development so there
> might be rough edges, missing pieces, etc. So we are quite interested
> in usage feedback and also don't mind doing a bit of hand-holding. So
> let me know how it goes or if there are any issues. In particular, if
> you have a lot of .blub, then writing ad hoc recipes could get tedious
> and that's where support for ad hoc rules could be helpful.
>
> [1] https://github.com/build2/libbuild2-rust
> [2] https://build2.org/release/0.13.0.xhtml#adhoc-recipe
> [3] https://lists.build2.org/archives/users/2020-July/000823.html