1166996 - rustc doesn't support MacOS X 10.6

Status: RESOLVED FIXED

(Firefox Build System :: General, defect)

Description

[Ralph Giles (:rillian)]

The rust standard library uses thread local storage features which are no supported in MacOS X versions prior to 10.7. Firefox still has many users on 10.6.

To ship rust code for Mac desktop we either need to drop 10.6 support, or figure out how to build rust code in a way that works there.

See https://github.com/rust-lang/rust/issues/25342 for upstream details.

Comment 1

[Ralph Giles (:rillian)]

Given the number of users affected, dropping 10.6 support isn't the correct choice this year, so we need to fix rust. Proposals include:

- building a custom rust toolchain with a pthread-based implementation of thread local storage

- adding shim or link pass to stub out the objectionable symbols at link time. Crashing is fine if they're called is fine until we drop 10.6 support.

Comment 2

[Alex Crichton [:acrichto]]

Now that https://github.com/rust-lang/rust/pull/25858 has landed, I believe that Gecko just needs to make sure to build its own Rust compiler and configure it with `--disable-elf-tls` and it should be good to go!

Comment 3

[Ralph Giles (:rillian)]

The --disable-elf-tls configure switch has been backported to the beta branch and will be 1.1.x, so we can build against a custom build of the stable toolchain that much sooner.

Remaining to unblock this to to modify gecko's configure script to check whether rustc is compatible with the MACOSX_DEPLOYMENT_TARGET so --enable-rust will reject inappropriate rust toolchains.

Comment 4

[Ralph Giles (:rillian)]

Rust 1.1.x backport is https://github.com/rust-lang/rust/pull/26371

Comment 5

[Ralph Giles (:rillian)]

We have workarounds for 1.1.x and later, so I'm closing this.

Some issues for follow-up work:
https://github.com/rust-lang/rust/issues/26581
https://github.com/rust-lang/rust/issues/27057