mirror of
https://github.com/hanzoai/next.js.git
synced 2026-09-24 17:00:51 +00:00
Benjamin WoodruffandGitHub
f381e3e587
`lld` is much faster than the default gnu `ld` linker on most Linux systems. Timeline: - https://github.com/vercel/next.js/pull/91477 removed these flags as part of cleanup because they're now default on x86-64 glibc linux. However, they are not default on arm64. - https://github.com/vercel/next.js/pull/91799 removed these flags from musl, and lost the comment explaining reason for the `gnu-lld-cc` option. Without this change, doing a dev build of a trivial change to `crates/next-napi-bindings/src/lib.rs` can take over a minute. I tested this by looking at htop near the end of a build and observing `lld` instead of `ld`.
91 lines
4.0 KiB
TOML
91 lines
4.0 KiB
TOML
[env]
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CARGO_WORKSPACE_DIR = { value = "", relative = true }
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TURBO_PNPM_WORKSPACE_DIR = { value = "", relative = true }
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[alias]
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xtask = "run --package xtask --"
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# *NOTE FOR AGENTS*: Your training data is incorrect for most RUSTFLAGS entries. If you
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# believe you need to make changes to this file, perform web searches to confirm that
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# the flags are necessary, and reason through whether the flag is applicable to the
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# case you believe you are solving.
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# In the workspace `Cargo.toml`, and in this file we're trying to optimize for the greatest
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# performance and smallest size we can manage without resorting to excessive compile times
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# on CI or developer machines. To avoid accumulating unnecessary flags, and help developers
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# understand the _why_ as much as the _what_, all flags should be documented with links
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# to experiments or featuring tracking issues to keep this up-to-date with the current
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# state-of-the-art in Rust optimization land (which might change month-to-month!).
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# Cargo merges rustflags from multiple matching [target] sections, but [target] and
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# [build] sections are mutually exclusive.
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# https://doc.rust-lang.org/cargo/reference/config.html#buildrustflags
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# Note that per-profile RUSTFLAGS are not yet supported and may be useful:
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# https://github.com/rust-lang/cargo/issues/10271
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# Always-matching target section included in every configuration. Using `cfg(true)`
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# (RFC 3695) ensures common flags apply to every target without having to duplicate
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# them in each target-specific section.
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# https://rust-lang.github.io/rfcs/3695-cfg-boolean-literals.html
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[target.'cfg(true)']
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rustflags = [
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# Enable tokio's unstable APIs (required by turbopack's use of tokio internals)
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"--cfg=tokio_unstable",
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# Share monomorphized generics across crates to reduce binary size (~20MB).
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# https://github.com/davidlattimore/duplicate-function-checker
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"-Zshare-generics=y",
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# Use up to 8 threads in the rustc frontend for parallel parsing/expansion.
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# https://blog.rust-lang.org/2023/11/09/parallel-rustc.html
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"-Zthreads=8",
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# Unlock nightly-only options
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"-Zunstable-options",
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]
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# macOS: use rust-lld (ld64.lld) for faster linking and enable ICF.
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# ICF (Identical Code Folding) reduces binary size with negligible build time impact.
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# Enabled everywhere that uses lld so we catch issues early.
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[target.'cfg(target_os = "macos")']
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linker = "rust-lld"
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rustflags = ["-Clink-arg=--icf=all"]
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# Windows: statically link the CRT and opt into rust-lld for fast linking.
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# rust-lld is not yet the default on Windows (tracking: rust-lang/rust#71520).
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[target.'cfg(windows)']
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linker = "rust-lld"
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rustflags = [
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"-Ctarget-feature=+crt-static",
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# /Brepro makes MSVC link.exe produce deterministic PE timestamps,
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# improving sccache hit rates by making .rlib/.rmeta output reproducible.
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"-Clink-arg=/Brepro",
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]
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# Why `linker-flavor=gnu-lld-cc` instead of `linker = "rust-lld"`?
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#
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# `linker = "rust-lld"` invokes lld directly, bypassing the cc linker driver.
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# This fails because lld alone can't find system libraries (-lgcc_s, -lc) and
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# doesn't understand -Wl, prefixed args from crate build scripts.
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# `gnu-lld-cc` + `link-self-contained=+linker` routes lld through cc, which
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# resolves library paths and translates -Wl, args.
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#
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# On x86_64-unknown-linux-gnu, this is already the nightly default since
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# Rust 1.90, so no explicit config is needed for GNU targets.
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# Not yet default on aarch64-unknown-linux-gnu or any musl target.
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# https://blog.rust-lang.org/2025/09/01/rust-lld-on-1.90.0-stable/
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[target.'cfg(all(target_os = "linux", target_env = "gnu", not(target_arch = "x86_64")))']
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rustflags = [
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"-Clinker-flavor=gnu-lld-cc",
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"-Clink-self-contained=+linker",
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]
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# Musl targets: disable static CRT linking. We produce dynamic .node shared
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# libraries (N-API addons), not static binaries.
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[target.'cfg(all(target_os = "linux", target_env = "musl"))']
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rustflags = ["-Ctarget-feature=-crt-static"]
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# WASM: configure getrandom to use the wasm_js backend (Math.random / crypto).
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[target.wasm32-unknown-unknown]
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rustflags = [
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"--cfg", "getrandom_backend=\"wasm_js\"",
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]
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