Hi Guillem and Raphaël, thank you two for jumping into it right away.
On Wed, Jul 09, 2025 at 01:26:27PM +0200, Guillem Jover wrote: > On Wed, 2025-07-09 at 12:39:12 +0200, Raphael Hertzog wrote: > > On Wed, 09 Jul 2025, Helmut Grohne wrote: > > So this part was added as part of the discussion in this bug report: > > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=453267 > > Right, was about to post the same reference. :) Thank you. Right in message #73 and later message #93 Raphaël questions precisely the code in question. In the later conversation, and message #78 in particular, we see that gcc did not override DEB_HOST_ARCH for dpkg-shlibdeps back then. There was a bit back and forth whether gcc could be updated to convey the architecture it is interested in more sanely, but the original approach ended up being merged. The -$DEB_TARGET_ARCH-cross packages that were mentioned there are still being built (unless applying the with_deps_on_target_arch_pkgs patchset and then they become :$DEB_TARGET_ARCH). Either way, gcc precisely tells apart what packages are meant to be target ones and for each of those it now (but now back then) changes DEB_HOST_ARCH to target for the dh_shlibdeps invocation. > …and from a quick skim over that report, I think this might have been > needed to support old gcc versions that had not yet been fixed to > use the expected variables (see messages #73 and forward)? (But this > was really a quick skim, so might have read the details wrong, as the > report is quite long.) Will try to recheck later today. I concur. This fully matches my understanding (see above). > > The right thing to try to validate whether we can remove the code is > > building a cross-compiler (and not cross-building a compiler). Running rebootstrap starts out with building a stage1 cross compiler, glibc stage2 and then a stage3 gcc cross compiler. Admittedly, it limits the amount of frontends to C, C++ and Fortran leaving out most other frontends. So building a full gcc-14-cross with that patch applied is something I likely should do still. Thankfully, we now have Debusine. :) https://debusine.debian.net/debian/developers/work-request/119889/ is a dpkg workflow and a gcc one shall go later. > Yes, I don't see rebootstrap using dpkg-buildpackage --target-arch for > anything except GNU mig? That is correct. The gcc source packages refuse to support DEB_TARGET_ARCH and you have to convey the target architecture via debian/target. In the end, it internally sets DEB_TARGET_* appropriately. > Ideally, we'd test both a cross-compiler build (build == host != target) > and a canadian cross-compiler build (build != host != target). I'm not sure canadian builds are supported at all. Do note that the canadian build should be unaffected. If build != host, $multiarch is overwritten and it no longer matters whether we set it when build != target. I argue that the proposed change does not affect canadian builds. Helmut
