How to Use mold or lld for Faster Linking in Rust

Add the rustflags configuration to your .cargo/config.toml to instruct the compiler to use mold or lld as the linker. For mold on Linux, add the following block to your config file:

[target.'cfg(target_os = "linux")']
rustflags = ["-C", "link-arg=-fuse-ld=mold"]

For lld, replace mold with lld in the flag value. This change applies to all builds in the current workspace and significantly reduces linking time by using a faster alternative to the default system linker.

Linking is the final step of building your Rust program where all the pieces are combined into one file. The default tool for this is often slow, especially for large projects. By telling Rust to use mold or lld, you swap that slow tool for a much faster one, making your builds finish in seconds instead of minutes.