Managed linkers

The default system selection preserves Cargo's linker. Change it when you want to try another linker or share a pinned choice across a workspace. Managed selections require clang on PATH. Keep system on Windows; managed rust-lld selection is not supported there.

Try a linker

On Linux, try a pinned mold release for one build:

MBX_LINKER=mold@2.42.0 mbx build

This is an example version, not an automatically updated recommendation. On Linux or macOS, rust-lld uses the active Rust toolchain's bundled LLD without a download:

MBX_LINKER=rust-lld mbx build

Selectors

mbx can select a linker by Cargo profile and target triple, install an exact version from its official GitHub releases, and route native Rust links through it. The built-in selectors are:

• system, which leaves Cargo's linker selection alone;
• rust-lld or lld, which uses the LLD shipped with the active Rust toolchain;
• mold@<version> or wild@<version>, which downloads the matching release asset and verifies GitHub's SHA-256 digest; and
• path:<executable>, which selects a linker mbx does not install.

Managed GitHub linkers require an exact version. Downloads are installed once beneath <cache_dir>/tools; concurrent builds share the same installation lock. GITHUB_TOKEN may authenticate GitHub API and download requests.

Within a profile table, an exact target triple wins over default. The top-level linker.default applies when the active profile has no entry. Cargo's ordinary profile is dev, --release selects release, cargo bench selects bench, and --profile <name> selects that custom profile.

[linker]
default = "system"

[linker.profiles.dev]
x86_64-unknown-linux-gnu = "mold@2.42.0"
aarch64-unknown-linux-gnu = "wild@0.10.0"

[linker.profiles.release]
default = "rust-lld"

MBX_LINKER overrides every file for one invocation:

MBX_LINKER=mold@2.42.0 cargo build
MBX_LINKER=system cargo build --release

mold and Wild currently provide managed releases for Linux. Unsupported host platforms fail before Cargo starts rather than silently changing the linker. The selected executable remains part of mbx's native-link cache identity.

Store persistent selections in your global configuration or in the workspace policy. The path: selector is accepted only outside repository-owned policy. A linker change can change cache keys; compare equivalent builds when measuring it.