[Bug 1957932] Re: [MIR] rustc, cargo

[Simon Chopin]

Built-Using is already used in all pure-Rust binaries, e.g. ripgrep.
However, it only stores the version of rustc itself. The non-vendored
libraries are currently recorded using the non-standard field 'X-Cargo-
Built-Using'. Sadly, this doesn't apply to all packages that currently
Build-Depend on rustc, only those that use the dh-cargo helper. src:0ad
for instance doesn't seem to record anything for that, nor does
src:cargo, ironically.

Furthermore, in the case of vendored dependencies, we've settled for
storing the "Cargo.lock" file which is a manifest of all the
dependencies of a given project with precise versioning. Currently for
rustc we ship it in /usr/share/doc/rustc/Cargo.lock

Regarding version bumps, it is worth noting that they already happen in
our other LTS versions. rustc 1.57 is indeed available in focal-updates
and bionic-updates. AIUI it's because of Firefox regularly needing a
newer version of rustc. Similarly, newer versions of LLVM are available
on older releases because of kernel and mesa requirements.

However, the versioned source name is a good point. On one hand it would
make sense because even though the rustc upstream tries their best not
to break existing code, breakage does occur from time to time, so
versioned rustc would make transitions easier. OTOH, rustc requires the
N-1 version to build (or itself), which would mean that we would have
the whole integer suite in the archive, which doesn't seem particularly
appealing to me given their 6-week cadence. I'll put it on Foundation's
agenda for the sprint next week.

I honestly cannot give you any expectations of how our handling of the
toolchain for 24.04 would be, as it will be shaped by the requirements
of the projects that will use it. I personally have some doubts that
we'll see *production* Rust code in our kernels for 24.04. I also
suspect that as the ecosystem matures we'll see less and less breaking
changes in rustc, as the long trail of unmaintained crates in crates.io
will calcify things a bit (they compile and run the tests for each crate
there for each release).

Thanks for the heads-up on the crossbeam issue, I'll update the affected
vendored version before uploading.

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https://bugs.launchpad.net/bugs/1957932

Title:
  [MIR] rustc, cargo

Status in cargo package in Ubuntu:
  Incomplete
Status in rustc package in Ubuntu:
  Incomplete

Bug description:
  [Availability]
  The packages rustc and cargo are already in Ubuntu universe.
  The packages build for the architectures they are designed to work on,
  and are also built on platform with lesser upstream support, see
  https://doc.rust-lang.org/nightly/rustc/platform-support.html for details.

  They currently build and works for architectures:
    * amd64
    * arm64
    * armhf
    * i386
    * ppc64el
    * riscv64
    * s390x

  Link to packages:

  https://launchpad.net/ubuntu/+source/rustc
  https://launchpad.net/ubuntu/+source/cargo

  Upcoming version:
  https://launchpad.net/~schopin/+archive/ubuntu/rustc-mir/+sourcepub/13264343/+listing-archive-extra

  
  [Rationale]
  The packages rustc and cargo are required in Ubuntu main as the Rust programming
  language is gaining in popularity, and those two packages are, respectively, its
  main compiler implementation and its dedicated build tool (and dependency manager).

  There are a few packages in main already that have partially switched to Rust
  as their implementation language, and so rustc and cargo will be needed to keep
  us in sync with their upstream. See for instance
  https://bugs.launchpad.net/ubuntu/+source/mdevctl/+bug/1942394 and
  https://lists.debian.org/debian-python/2021/12/msg00000.html
  (python-cryptography is in main)

  Note that the huge majority of our users will not use these packages, their
  purpose is to be a build-dependency for other packages. In particular, it is
  not particularly expected at this stage that those of our users that are Rust
  developers, which usually rely on their toolchain being managed in their $HOME
  by the `rustup` tool.

  [Security]
  cargo and rustc had 19 recorded security issues in the past, mostly in the Rust standard library
  (1 affecting cargo):

  https://nvd.nist.gov/vuln/search/results?form_type=Advanced&results_type=overview&search_type=all&isCpeNameSearch=false&cpe_vendor=cpe%3A%2F%3Arust-
  lang&cpe_product=cpe%3A%2F%3A%3Arust

  All issues are usually handled promptly by the Rust team. However, the fixes
  are rarely (if ever) backported to previous releases besides an occasional
  1.X.1 point release for the latest stable.

  There is an official Rust Security working group that curates a database of security
  issues within the Rust ecosystem, including rustc/cargo:

  https://github.com/rustsec/advisory-db

  - no `suid` or `sgid` binaries
  - no executables in `/sbin` and `/usr/sbin`
  - Package does not install services, timers or recurring jobs
  - Packages does not open privileged ports (ports < 1024)
  - Packages does not contain extensions to security-sensitive software
  (filters, scanners, plugins, UI skins, ...)

  Note however that in typical use, building a project with cargo+rustc involves
  executing code that has been downloaded from crates.io: cargo builds and executes
  the `build.rs` file for any pre-compilation task (a bit like a Makefile), and any use
  of a proc macro dependency basically implies running arbitrary code (the macro) within
  the execution context of rustc.

  [Quality assurance - function/usage]
  The packages work well right after install, one can easily create a simple Rust project
  and run it.

  [Quality assurance - maintenance]
  The packages do not deal with exotic hardware we cannot support

  [Quality assurance - testing]
  The packages both run a test suite on build time. However, the rustc test suite
  does NOT make the build fail as of 1.57. The reason is that there are always a few tests that fail, and it was a tradeoff made due to limited resources. Please note that Debian has a strategy of only failing the build if there are *too many* errors. As the Foundations team commits more resources on this toolchain, we've reverted back to Debian's system and are planning to making the testing story more rigorous.

  Neither package has any autopkgtests in the versions currently in the
  release pocket. The upcoming rustc upload will have an autopkgtest
  consisting of rebuilding itself. Debian's cargo package now has a
  similar autopkgtest, that will be cherry-picked in the next cargo
  upload.

  [Quality assurance - packaging]
  debian/watch is present and works

  rustc yields quite a bit of lintian output, but they seem mostly harmless.
  https://lintian.debian.org/sources/rustc

  There are lintian overrides present, but those are usually justified in the override
  files themselves.

  cargo is a bit more tame on the warning fronts
  https://lintian.debian.org/sources/cargo

  It has an override file for the source package, for relatively minor
  warnings.

  These packages does not rely on obsolete or about to be demoted
  packages.

  The packages will not be installed by default

  The packaging is fairly complex, especially in the case of rustc. The crux of
  the complexity can be attributed to the boostrapping issue, as well as the need
  to deal with vendored dependencies. There is extensive documentation within the
  debian/ directories to help with the difficulties, and a lot of things have been
  automated in scripts living in debian/scripts/*

  Note that originally, the upstream tarball for rustc includes the sources for
  cargo as well as its vendored dependencies, but the Debian Rust team chose to
  split it out in its own package.

  [UI standards]
  I do not believe there's a need for translation for these applications given the
  stated purpose for having them in main.

  [Dependencies]
  The packages have quite a few vendored dependencies. However, their non-vendored
  dependencies are all in main, as well as the build-dependencies, assuming for the purpose
  of this analysis that src:rustc is in main.

  [Standards compliance]
  The packages violate the Debian Policy on vendored
  dependencies, with a copy of libgit2 (as a delta to Debian) in cargo.

  The upcoming 1.58.1+dfsg1~ubuntu1 version of src:rustc unbundles the
  LLVM copy that's currently in src:rustc.

  [Maintenance/Owner]
  Owning Team will be Foundations
  Team is not yet, but will subscribe to the package before promotion

  Both packages use static linking for the Rust dependencies, as well as any
  vendored C dependency (i.e. libgit2).

  rustc uses vendored rust code tracked in Cargo.lock as shipped, in the package,
  refreshing that code works via `cargo update ...` + cargo vendor

  cargo has a different process, documented in debian/README.source.
  TODO: actually try to update a dependency in cargo using the debian/README.source,
  which are not that clear.

  [Background information]
  The Package descriptions explains the package well
  Upstream Name is developed by the Rust Compiler team and the Cargo team, under
  the umbrella of the Rust Foundation
  Link to upstream project: https://www.rust-lang.org/

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