jemalloc in 1.21.0 doesn't work on iOS

[michaelfairley]

Jemalloc 4.5.0 (first included in 1.21.0) immediately aborts when run on ARM iOS devices. (Upstream issue). Fortunately, the underlying issue seems to have been fixed in jemalloc 5.0.0 and onwards. (Unfortunately, a Rust PR to upgrade to 5.0.1 just got closed: #45163).

Using the system allocator is an okay workaround for now (though, it requires using nightly).

[sfackler]

It sounds like you tracked the commit that fixed it down? We may be able to cherry-pick that onto our 4.5.0 fork to avoid having to go debug Android.

[arthurprs]

I don't think that change can be backported easily. I guess the best option would be to use system allocator in this platform.

[kali]

Should we consider just disabling jemalloc for iOS ? My understanding is that the only real use-case for iOS rust executables is tests and bench using dinghy or some other contraption of the same kind so the impact feels minimal.

[michaelfairley]

My understanding is that the only real use-case for iOS rust executables is tests and bench...

I definitely ship apps with rust executables to the App Store. 😐

I'd be fine with disabling jemalloc in lieu of the system allocator until some future jemalloc upgrade.

[kali]

Ha, good to know :) We only ship libraries, but we do like our tests... I am working on a PR with jemalloc disabled.

[SimonSapin]

@michaelfairley Should this be closed, after #46211 ?

[michaelfairley]

I suppose! #46211 definitely has me running and happy.

It's probably worth tracking this somewhere though, since it's probably ideal to reenable jemalloc on iOS after a future jemalloc upgrade.

[SimonSapin]

Ok, thanks! Closing.

Per #36963 the plan is to remove jemalloc from the standard library, so this will become a non-issue there. Try https://crates.io/crates/jemallocator and see if it works for you? I think these days it uses jemalloc 5.0.x