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Hack fix for ICE as seen in CI #23295

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Feb 23, 2022
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18 changes: 18 additions & 0 deletions runtime/src/builtins.rs
Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,24 @@ pub enum BuiltinFeatureTransition {
},
}

// https://github.com/solana-labs/solana/pull/23233 added `BuiltinFeatureTransition`
// to `Bank` which triggers https://github.com/rust-lang/rust/issues/92987 while
// attempting to resolve `Sync` on `BankRc` in `AccountsBackgroundService::new` ala,
//
// query stack during panic:
// #0 [evaluate_obligation] evaluating trait selection obligation `bank::BankRc: core::marker::Sync`
// #1 [typeck] type-checking `accounts_background_service::<impl at runtime/src/accounts_background_service.rs:358:1: 520:2>::new`
// #2 [typeck_item_bodies] type-checking all item bodies
// #3 [analysis] running analysis passes on this crate
// end of query stack
//
// Yoloing a `Sync` onto it avoids the auto trait evaluation and thus the ICE.
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Which is safe because the compiler was cool with the same types in tuple form before #23233, right?

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True, but how about adding some extra checks to ensure that our assumptions aren't broken in the future. Here are my suggested changes: t-nelson#32

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I'm not sure I understand the benefit. Commented over there

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@jstarry what assumptions are you referring to that may be broken in the future?

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@jackcmay the unsafe impl can introduce undefined behavior because the compiler won't complain if they are added for types which are not thread-safe.

//
// We should remove this when upgrading to Rust 1.60.0, where the bug has been
// fixed by https://github.com/rust-lang/rust/pull/93064
unsafe impl Send for BuiltinFeatureTransition {}
unsafe impl Sync for BuiltinFeatureTransition {}

impl BuiltinFeatureTransition {
pub fn to_action(
&self,
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