How to express inter-directory dependencies in <bsd.*.mk> infrastructure?

[mdf at FreeBSD.org]

2011/10/30 Lev Serebryakov <lev at freebsd.org>:
> Hello, Hackers.
>
>  (SORRY FOR SENDING INCOMPLETE MESSAGE)
>
>  How to express inter-directory dependencies in <bsd.*.mk> infrastructure?
>
>  I have project, which has two subdirectories: "lib" and "bin".
>  Top-level Makefile is simple one, looks like this:
>
> ===================================
> SUBDIR= lib \
>        bin
>
> .include <bsd.subdir.mk>
> ===================================
>
>  "lib" subdirectory has Makefile with "<bsd.lib.mk>" included, and
>  "bin" -- with <bsd.prog.mk> included.
>
>  But how could I express, that PROG in bin depends on LIB from lib, to
> cause rebuilding of PROG when LIB is changed (when I call "make" on
> top level)?

Normally I'd expect the dependency to be handled by make depend; that
is, the source for the binary should be #including header files from
the library.  If the interfaces change, make depend will handle this.

I guess the problem comes if you are using static linking and just
implementation details internal to the library change.

There is a DPADD makefile variable that seems to be used; I'm not sure
though if this handles the type of dependency you're wanting.

Cheers,
matthew