Rust 1.97.0 defaults to the v0 symbol mangling scheme

Category: Languages
Status: confirmed
Sources: Rust 1.97.0 release
Summary: The Rust project released 1.97.0 on 2026-07-09. The compiler now uses the v0 symbol mangling scheme by default, which can require newer debuggers and profilers to demangle symbols and changes the formatting of text in backtraces. The release also prevents an unsound deref coercion in the pin! macro, so pin!(x) where x is &mut T now produces Pin<&mut &mut T> rather than sometimes coercing to Pin<&mut T>, and it warns on linker output by default. Cargo stabilizes build.warnings, which controls how local-package lint warnings are treated and can enforce a warning-free CI build in place of -Dwarnings, plus resolver.lockfile-path. New stabilized APIs include integer bit-manipulation helpers such as isolate_highest_one, highest_one, and bit_width.
Why it matters: The v0 mangling default and the pin! soundness fix are behavior changes that can surface in profiling and debugging tooling and in code that relied on the previous coercion, so they warrant attention on upgrade.
Follow-up: Watch for tooling that fails to demangle v0 symbols and any code broken by the tightened pin! coercion.