fix: -Cmetadata includes whether extra rustflags is same as host #14432
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See rust-lang/cargo 14253
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epage
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Aug 21, 2024
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| let target_configs_are_different = unit.rustflags != host_info.rustflags | ||
| || unit.rustdocflags != host_info.rustdocflags | ||
| || bcx | ||
| .target_data | ||
| .target_config(CompileKind::Host) | ||
| .links_overrides | ||
| != unit.links_overrides; |
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This feels a bit brittle. If we don't remember to update this with anything else that is different but not in metadata already, we'll see this problem again.
The only thoughts I had are
- Putting this question in the unit or host info to answer
- Hashing
unit.kind.is_host() && !bcx.gctx.target_applies_to_host().unwrap_or_default()
Note: answering this is more important for long term reliability and stabilization. This doesn't need to block fixing people who are using the unstable feature
epage
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Aug 21, 2024
`-Ztarget-applies-to-host --config target-applies-to-host=false` make it possible to build two units for the same output directory with different rustflags (one with artifact/target rustflags, one with none/host rust flags). Those flags aren't included in the `-Cmetadata` hash which is used to disambiguate different versions of crates, resulting in a conflict. The actual error being produced appears to be the result of two invocations of `rustc` racing and clobbering each other. While we don't hash RUSTFLAGS because it may contain absolute paths that hurts reproducibility, we track whether a unit's RUSTFLAGS is from host config, so that we can generate a different metadata hash for runtime and compile-time units.
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Removed the comment and added a note above the hack. Thanks people. Going to merge this. @bors r=epage |
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Update cargo 12 commits in ba8b39413c74d08494f94a7542fe79aa636e1661..8f40fc59fb0c8df91c97405785197f3c630304ea 2024-08-16 22:48:57 +0000 to 2024-08-21 22:37:06 +0000 - Tests rely on absence of RUST_BACKTRACE (rust-lang/cargo#14441) - fix: -Cmetadata includes whether extra rustflags is same as host (rust-lang/cargo#14432) - [mdman] Normalize newlines when rendering options (rust-lang/cargo#14428) - fix: doctest respects Cargo's color options (rust-lang/cargo#14425) - Be more permissive while packaging unpublishable crates. (rust-lang/cargo#14408) - fix: Limiting pre-release match semantics to use only on `OptVersionReq::Req` (rust-lang/cargo#14412) - test: add a regression test for Issue 14409 (rust-lang/cargo#14430) - chore: update label trigger for Command-info (rust-lang/cargo#14422) - doc: add lockfile-path unstable doc section (rust-lang/cargo#14423) - doc: update lockfile-path tracking issue (rust-lang/cargo#14424) - fix: remove list owners feature of info subcommand (rust-lang/cargo#14418) - Lockfile path tests (follow-up) (rust-lang/cargo#14417)
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What does this PR try to resolve?
Fixes #14253
The root cause is described in #14253 (comment):
While we don't hash RUSTFLAGS because it may contain absolute paths that
hurts reproducibility, we track whether a unit's RUSTFLAGS is from host
config, so that we can generate a different metadata hash for runtime
and compile-time units.
How should we test and review this PR?
This hack is only enabled when
target-applies-to-host=falseand when compile kind is the host platform, so the shouldn't affect any stable behavior.Additional information
cc @gmorenz
I found time working on this PR before my travel. Feel free to cherry pick and create a new PR if this is not correct.