[gentoo-dev] HDEPEND (host dependencies for cross-compilation) for EAPI 5?

[Zac Medico]

For those who may not know, chromium-os currently uses a
hard-host-depends ebuild as a workaround for our lack of HDEPEND support
[1]. We could easily add HDEPEND in EAPI 5 if we want, since we already
have a Portage patch attached to bug #317337 [2]. Here is a summary of
what that Portage patch will do:

In EAPI 5 or later, DEPEND has been divided into two parts:
DEPEND for build-time target dependencies, and HDEPEND for
build-time host dependencies. This division is designed
specifically to minimize difficulty in the process of
adapting ebuilds that were written for earlier EAPIs,
and therefore it also minimizes the adjustments that
ebuild developers will have to make to the thought
processes involved when writing ebuilds from scratch. In
an environment that does not involve cross-compilation,
HDEPEND behaves the same as DEPEND. When an ebuild is
converted from EAPI 4 or earlier to EAPI 5 or later,
in order to support cross-compilation environments, some
dependencies may need to be migrated to HDEPEND.

For ebuilds that have EAPI 5 or later, the emerge
--root-deps option has no effect since it is made obsolete
by division between DEPEND and HDEPEND. If EAPI 4 or
earlier ebuilds are used in combination with EAPI 5 or
later ebuilds, the --root-deps behavior will still be
applied to the EAPI 4 or earlier ebuilds (there is no
behavior change for ebuilds having older EAPIs).

[1]
http://www.chromium.org/chromium-os/how-tos-and-troubleshooting/portage-build-faq
[2] https://bugs.gentoo.org/show_bug.cgi?id=317337
-- 
Thanks,
Zac