Sergei Trofimovich schrieb: > On Sun, 20 Jan 2013 20:11:31 +0100 > Michał Górny <mgo...@gentoo.org> wrote: > >> Hello, >> >> There is a fair interest in multilib and while still early, it would be >> a good moment to decide on how USE flags to use for it. >> >> The current attempts are mostly using USE=multilib which is not really >> expressive and poor. What I would go for is a clear variable specifying >> which targets package is built for. > > You just need to add 'ABI' and 'MULTILIB_ABIS' to > "emerge --info ${pkg}" output. > > Do you plan to keep precise depends for packages? > like glibc[abi_x32]/gcc[abi_x32] for all libraries requesting x32. > > What to do if someone builds a package only with non-default ABI? > (it means installed package does not quite work for default ABI) > > like on ABI=amd64 media-libs/glu[ABI=x32] could not be used by > any of ABI=amd64 users. > > In order to track such depends precisely you would need to add > ABI flags to each revdep recursively. It's quite invasive. Is it worth > the effort? > > Currently USE=multilib means 'build for all toolchain-supported' ABIs. > It looks clean and short. > >> This raises the following questions: >> >> 1) do we want the default ABI to be switchable? > It already is via /etc/portage/env per-package. > Or via profile globally. arch/amd64/make.defaults: > MULTILIB_ABIS="amd64 x86" > > DEFAULT_ABI="amd64" > > crossdev allows bootstrapping with any random default > ABI out there as one-liner: > crossdev -A 'x32 amd64' x86_64-unknown-linux-gnu. > >> 2) do we want irrelevant ABIs to be visible to emerge users? >> >> By 2) I mean: do we want the users to see stuff like: >> >> MULTILIB_ABIS="amd64_abi1 amd64_abi2 -amd64_abi3 (-ppc64_abi1) >> (-ppc64_abi2) (-ppc64_abi3) ..." > > Would adding irrelevant ABIs trigger rebuilds on world update? > > Do you intermingle gentoo's $ARCH and ABI? > How many ABI vars do you expect to see for simple "common" cases? > > x86_64-pc-linux-gnu-gcc -m32 (host ARCH=amd64) > x86_64-pc-linux-gnu-gcc -m64 (host ARCH=amd64) > x86_64-pc-linux-gnu-gcc -mx32 (host ARCH=amd64) > i686-pc-linux-gnu-gcc -m32 (host ARCH=x86) > i686-pc-linux-gnu-gcc -m64 (host ARCH=x86) > i686-pc-linux-gnu-gcc -mx32 (host ARCH=x86) > > 3 or 6? > > Looks like insane amount of metadata growth for each > plagued package. > >> or just the relevant part. >> >> To be honest, I don't know if there's other way to hide USE flags than >> using USE_EXPAND_HIDDEN. If we want to use that, we'd have to split >> the flags per-arch, i.e. have: >> >> MULTILIB_AMD64="abi1 abi2 abi3" >> MULTILIB_PPC64="abi1 abi2 abi3" >> >> with appropriate USE_EXPAND_HIDDEN set by profiles. > > Having direct support in portage's core might reduce amount of > user-visible/storable metadata in main tree. No slightest idea > how it would look like though. >
Support for cross-compiling packages for toolchain-supported ABIs already exists and works for some years in multilib-portage (code in the multilib branch of portage git repo, ebuild in the multilib-portage overlay with very basic setup instructions in the doc dir of the overlay and the #gentoo-multilib-overlay channel in freenode for questions). -- Thomas Sachau Gentoo Linux Developer
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