Package: pbuilder Severity: wishlist Hi Mattia,
thanks for your work on pbuilder and your interest in making it work for cross building as well. As discussed with you, this bug is supposed to serve as an implementation plan to make pbuilder support cross building. The first part to supporting cross building is to extend the user interface in a way exposing the functionality. This implies distinguishing the "build" architecture from the "host" architecture. Currently pbuilder only knows about one architecture given via --architecture. The documentation of this option needs clarification which architecture(s) it refers to. Furthermore pbuilder needs a means to select a host architecture that differs from the build architecture. Unless the --architecture switch is to be interpreted as host architecture and the build architecture is taken from the base.tgz, a new option is required here. Defaults should be picked such that the build architecture and the host architecture coincide as native building still is predominant. Internally, pbuilder should probably start differentiating those two architectures and expose them via shell variables, so internal functions and hooks can refer to them. When doing cross-specific things, pbuilder should not carry a boolean to determine whether a cross build is in operation, but instead use an equality test on the build and host architectures. I am mentioning this here, because debomatic got this wrong initially. During a cross build, pbuilder should dpkg --add-architecture the host architecture in the chroot (unless the chroot already has that architecture added). The dependency resolver needs to make use of the host architecture. In the simplest case, the experimental apt comes to unstable and all you have to do is pass --host-architecture to "apt-get build-dep foo.dsc". When using pbuilder's internal resolvers, things look less bright. It is not clear to me, whether making those resolvers cross-aware is worth the effort. Unless apt takes care, pbuilder should install crossbuild-essential-$DEB_HOST_ARCH before satisfying Build-Depends. In a distant future, this might turn out unneeded, but for now and stretch this is how things will be done. Next, dpkg-buildpackage as invoked by pbuilder needs to be told about the host architecture. Maybe other tools (such as dpkg-checkbuilddeps) also need such awareness. I think that everything beyond the dependency resolver change can be implemented without waiting. To test the result (without a working dependency resolver), you can create a special base.tgz that already has crossbuild-essential-$somearch installed and build a package with trivial cross dependencies. Examples are: attr base-files bzip2 dash db-defaults debianutils diffutils findutils gdbm gmp gzip hostname keyutils kmod libatomic-ops libelf libpthread-stubs libseccomp libsepol libtextwrap libunistring libxau libxdmcp mawk openssl patch pcre3 tcltk-defaults ustr xz-utils I hope that this covers most things, but in the interest of getting things right, I X-Debbugs-Cced d-cross@l.d.o so those who disagree can easily follow up. Helmut
