On Thu, 08 Jun 2023 at 19:22:02 -0400, nick black wrote: > Simon McVittie left as an exercise for the reader: > > Debian-style multiarch or Fedora/Arch-style multilib is a much, much > > this is at least the second time you've drawn this distinction > in this thread. for anyone else who, like me, was uneasy with > their understanding of the concept
Sorry, I spend a lot of my work time immersed in this sort of thing and how it differs between distributions, so I tend to forget that most developers are able to stick to one distro and don't need to know this! I think this is important background knowledge for anyone who wants to change how we handle architectures that are generally used as a foreign architecture, particularly i386. > https://wiki.debian.org/ToolChain/Cross#Multiarch_vs_Multilib That's talking about the different gcc toolchains, but I actually meant the difference in how libraries are packaged, which is a slightly separate concept but tends to go together. Readers of this thread are hopefully all familiar with Debian multiarch, where the linker (both runtime and compile-time) searches /{usr/,}lib/x86_64-linux-gnu, /{usr/,}lib/i386-linux-gnu or equivalent non-x86 paths, as appropriate for the architecture, and we install shared libraries to those paths. The dynamic string token ${LIB} (see ld.so(8)) expands to lib/x86_64-linux-gnu or similar. Fedora and its relatives (RHEL, CentOS and so on) use the directory layout described by LSB/FHS, in which i386 libraries are installed into /usr/lib and x86_64 libraries into /usr/lib64 (a "libQUAL" directory using FHS terminology), and the runtime and compile-time linkers search those paths as appropriate for the architecture. They install most libraries for x86_64 only, from packages like glib2-*.x86_64.rpm, into /usr/lib64. A subset of libraries (enough to support Wine and legacy i386 binaries) are also available for i386, from packages lke glib2-*.i686.rpm, into /usr/lib. The dynamic string token ${LIB} expands to lib64 or lib as appropriate. Arch Linux and its relatives (Manjaro and so on) use the reverse of Fedora's layout: they mostly install x86_64 libraries from packages like glib2-*-x86_64.pkg.tar.zst into /usr/lib, and a subset of libraries are also available for i386, from packages like lib32-glib2-*-x86_64.pkg.tar.zst, installing into /usr/lib32. ${LIB} expands to lib or lib32 as appropriate. Other distributions *usually* match one of those families (often the same as Fedora, for example openSUSE and Gentoo seem to match that), but there are exceptions, like Exherbo which sets the ${prefix} to /usr/GNU_TUPLE for each architecture, resulting in libraries in /usr/GNU_TUPLE/lib. Debian *mostly* uses multiarch, but we still have a small subset of packages that install a library of a different architecture to the libQUAL directories, for use with multilib compilers. On x86_64 they're named like lib32stdc++6_*_amd64.deb and follow the Arch-like directory layout with a lib32 directory, while on i386 they're named like lib64stdc++6_*_i386.deb and follow the Fedora-like layout with a lib64 directory. smcv
