Paolo Bonzini <pbonz...@redhat.com> writes: > On Tue, Jul 9, 2024 at 2:09 PM Peter Maydell <peter.mayd...@linaro.org> wrote: >> * what is the actual baseline requirement? We definitely want >> to support "using rustup on an older system" (should be no >> problem) and "current distro building QEMU using the distro's >> rust", I assume. It would certainly be nice to have "building >> QEMU on the older-but-still-in-our-support-list distro releases >> with that distro's rust", but this probably implies not just >> a minimum rust version but also a limited set of crates. > > I don't think limiting ourselves to the set of crates in the distro is > feasible. It's not the way the language works, for example I tried > checking if the "cstr" crate exists and I didn't find it in Debian. > > We can define a known-good set of versions: > * either via Cargo.lock (i.e. recording the versions and downloading > them) or by including sources in the tree > * at any time in qemu.git, at branching time (three times a year), or > on every release > > (That's six possibilities overall). > >> I think (but forget the details) that some of what we've done >> with Python where we accept that the older-but-still-supported >> distro will end up taking the "download at build time" path >> in the build system might apply also for Rust. > > Yes, and --without-download may be changed to the "--frozen" flag of cargo. > >> * what, on the Rust side, is the version requirement? Presumably >> there's some features that are pretty much "we really need >> this and can't do without it" and some which are "this would >> be pretty awkward not to have but if we have to we can implement >> some kind of fallback/alternative with a TODO note to come >> back and clean up when our baseline moves forwards". > > Here are the stopping points that I found over the last couple weeks: > > 1.56.0: 2021 edition > 1.59.0: const CStr::from_bytes_with_nul_unchecked (needed by cstr > crate, see below) > 1.64.0: std::ffi::c_char > 1.65.0: Generic Associated Types > 1.74.0: Clippy can be configured in Cargo.toml > 1.77.0: C string literals, offset_of! > > I think 1.59.0 is pretty much the lower bound. Not having offset_of! > will be a bit painful, but it can be worked around (and pretty much > has to be, because 1.77.0 is really new). > > As far as I understand, Debian bullseye has 1.63.0 these days and it's > the oldest platform we have.
I was going to say Bookworm has now superseded Bullseye which will reach its release + 3 year support point in August. However the version you mention in the Bookworm one! > > Paolo > >> At that point we have more information to figure out what >> if any tradeoff we want to make. >> >> thanks >> -- PMM >> -- Alex Bennée Virtualisation Tech Lead @ Linaro
