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Release builds fail on macOS 27: Rust 1.95 strips proc-macro dylibs with misaligned __LINKEDIT (fixed in Rust 1.98)

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Assessment

Difficulty
1/5
Estimated time
Under an hour
Newbie friendliness
80/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
macos, rust
Domain
build-system

Research direction

The fix is a one-line change to the channel in rust-toolchain.toml at the repo root, bumping the pin from 1.95.0 to 1.98.0 or later (1.99.0 is current stable). Verify with cargo build --release -p buzz-db on macOS 27, which previously failed with the mis-aligned LINKEDIT dlopen error; the sqlx-macros dylib loading is the signal that it worked. Check #8049 first, since it upgrades Hermit-managed tools while keeping the pin at 1.95.0 and may conflict.

Written by the indexing model from the issue text.

Description

Summary

On macOS 27, cargo build --release of any crate that uses sqlx macros fails with the pinned Rust 1.95.0 toolchain. The cause is a known LLVM bug that is already fixed in Rust 1.98.0, so bumping rust-toolchain.toml to 1.98 or later resolves it. (#8049 upgrades the Hermit-managed tools but keeps the pin at 1.95.0.)

Reproduction

  • macOS 27.2 (26B5091g), Xcode 27.0, arm64, at block/buzz main with the pinned toolchain:
$ cargo build --release -p buzz-db
error: …/libsqlx_macros-<hash>.dylib: dlopen(…): … mis-aligned LINKEDIT string pool, fileOffset=0x008730AC
error[E0432]: unresolved imports `self::encode::Encode`, …
error: could not compile `sqlx` (lib) due to 2 previous errors
  • cargo check and tests pass, because the dev profile doesn't strip. Release builds of buzz-relay and anything else that depends on sqlx macros fail the same way.

Root cause

  • Cargo's release profile defaults to strip = "debuginfo". On macOS, rustc strips with its bundled rust-objcopy (LLVM), not Apple's strip.
  • LLVM's Mach-O objcopy wrote __LINKEDIT entries at offsets that are only 4-byte aligned, which macOS 27's dyld now rejects.
  • Upstream reports and fixes:
    • rust-lang/rust#157750
    • llvm/llvm-project#203678, fixed by llvm/llvm-project#203680
    • picked up in rust-lang/rust#158410, milestone 1.98.0

Checked on the same sqlx-macros dylib:

Step Result on macOS 27.2
Unstripped loads
Apple strip -S / strip -x loads
LLVM objcopy --strip-debug (Rust 1.95 / 1.96 / 1.97.1) mis-aligned LINKEDIT string pool
cargo build --release -p buzz-db on Rust 1.99.0 builds; dylib loads

Small proc-macro dylibs often pass by luck of alignment, which is why a trivial repro may not trigger it. The sqlx-macros dylib Buzz builds (~12 MB, with Buzz's sqlx features) triggers it reliably.

Suggested fix

Bump rust-toolchain.toml to 1.98.0 or later (current stable is 1.99.0).

Until then, this workaround disables stripping only for build-time artifacts (proc macros, build scripts) and leaves shipped binaries unchanged:

CARGO_PROFILE_RELEASE_BUILD_OVERRIDE_STRIP=none cargo build --release

or

[profile.release.build-override]
strip = "none"
Dominant language
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Avg merge
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Merged PRs (30d)
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