On 05/10/2017 11:52 AM, Wookey wrote: > Debian requires packages to run on the base level ISA defined for each > architecture (which does change slowly over time).
Well, kind of. What Debian requires is that if it is at all feasible software should run on the base ISA - which in practice means that very often the software is only compiled for the base ISA itself, resulting in the binaries being slower than they need to be on more modern hardware. However, there are a couple of packages that can't easily be ported to the base ISA (such as packages that use tons of SSE assembly, which allows those packages to be run on some 32bit x86 CPUs), an in this case the consensus was that it's better to have the packages in Debian at all, even if they aren't available for all users. That said, in those cases the basic constraints were that suitable run-time checks need to be available to produce an error that the user can understand (and not just fail with SIGILL), and to still consider the fact that it doesn't run on the base ISA as a bug in the package, just not a RC bug. (The rationale why this is not considered RC is the following: take for example the case of SSE-assembly-heavy code, which can't easily be made to work with x87 FPU-only systems. If missing base ISA support in that case were to be RC, then the only alternative would be to just drop i386 support completely, which is a worse outcome because then nobody on i386 could use the package.) With that all out of the way: if a package does support being compiled for the base ISA, or a patch to make it work is trivial, then it would be considered RC (on release archs at least) not supporting the base ISA in the compiled package. What's not required is to also compile optimized versions that run faster on newer hardware - but in an ideal world one would also like to do that. (With gcc's function multi-versioning (FMV) this has become a lot easier noawadays though.) Regards, Christian
