`#[no_link]` attribute does not prevent crate linking

[martonmoro]

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Problem: #[no_link] does not prevent an extern crate from being linked.

Steps to reproduce:

macro_crate/Cargo.toml:

[package]
name = "macro_crate"
version = "0.1.0"
edition = "2021"

macro_crate/src/lib.rs:

#[macro_export]
macro_rules! square {
    ($x:expr) => {
        $x * $x
    };
}

pub fn add(x: i32, y: i32) -> i32 {
    x + y
}

Cargo.toml:

[package]
name = "no_link_bug"
version = "0.1.0"
edition = "2024"

[dependencies]
macro_crate = { path = "../macro_crate" }

src/main.rs:

#[no_link]
extern crate macro_crate;

fn main() {
    let num = 4;
    let squared = macro_crate::square!(num);
    println!("{} squared is {}", num, squared);

    let sum = macro_crate::add(1, 2);
    println!("1 + 2 = {}", sum);
}

Expected behavior:
The build should fail with a linker error, for example:

rust-lld: error: undefined symbol: macro_crate::add::hd706c5be871dff6f

Actual behavior:
The build succeeds and produces a binary.

Meta:

rustc 1.95.0-nightly (c04308580 2026-02-18)
binary: rustc
commit-hash: c043085801b7a884054add21a94882216df5971c
commit-date: 2026-02-18
host: x86_64-unknown-linux-gnu
release: 1.95.0-nightly
LLVM version: 22.1.0

cargo 1.95.0-nightly (ce69df6f7 2026-02-12)

Linux x86_64

Verbose build output:

Verbose output

RUST_BACKTRACE=1 cargo build -vv
Compiling macro_crate v0.1.0 (/home/mmoro/Projects/no_link_bug/macro_crate)
     Running `CARGO=/home/mmoro/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo CARGO_CRATE_NAME=macro_crate CARGO_MANIFEST_DIR=/home/mmoro/Projects/no_link_bug/macro_crate CARGO_MANIFEST_PATH=/home/mmoro/Projects/no_link_bug/macro_crate/Cargo.toml CARGO_PKG_AUTHORS='' CARGO_PKG_DESCRIPTION='' CARGO_PKG_HOMEPAGE='' CARGO_PKG_LICENSE='' CARGO_PKG_LICENSE_FILE='' CARGO_PKG_NAME=macro_crate CARGO_PKG_README='' CARGO_PKG_REPOSITORY='' CARGO_PKG_RUST_VERSION='' CARGO_PKG_VERSION=0.1.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=1 CARGO_PKG_VERSION_PATCH=0 CARGO_PKG_VERSION_PRE='' LD_LIBRARY_PATH='/home/mmoro/Projects/no_link_bug/target/debug/deps:/home/mmoro/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib' /home/mmoro/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustc --crate-name macro_crate --edition=2021 macro_crate/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=192 --crate-type rlib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=1ffd961baa1102b0 -C extra-filename=-c0993a15f8871f25 --out-dir /home/mmoro/Projects/no_link_bug/target/debug/deps -C incremental=/home/mmoro/Projects/no_link_bug/target/debug/incremental -L dependency=/home/mmoro/Projects/no_link_bug/target/debug/deps`
   Compiling no_link_bug v0.1.0 (/home/mmoro/Projects/no_link_bug)
     Running `CARGO=/home/mmoro/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo CARGO_BIN_NAME=no_link_bug CARGO_CRATE_NAME=no_link_bug CARGO_MANIFEST_DIR=/home/mmoro/Projects/no_link_bug CARGO_MANIFEST_PATH=/home/mmoro/Projects/no_link_bug/Cargo.toml CARGO_PKG_AUTHORS='' CARGO_PKG_DESCRIPTION='' CARGO_PKG_HOMEPAGE='' CARGO_PKG_LICENSE='' CARGO_PKG_LICENSE_FILE='' CARGO_PKG_NAME=no_link_bug CARGO_PKG_README='' CARGO_PKG_REPOSITORY='' CARGO_PKG_RUST_VERSION='' CARGO_PKG_VERSION=0.1.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=1 CARGO_PKG_VERSION_PATCH=0 CARGO_PKG_VERSION_PRE='' CARGO_PRIMARY_PACKAGE=1 LD_LIBRARY_PATH='/home/mmoro/Projects/no_link_bug/target/debug/deps:/home/mmoro/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib' /home/mmoro/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustc --crate-name no_link_bug --edition=2024 src/main.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=192 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=6bf287f543d40f7f -C extra-filename=-838203c1bd20a69b --out-dir /home/mmoro/Projects/no_link_bug/target/debug/deps -C incremental=/home/mmoro/Projects/no_link_bug/target/debug/incremental -L dependency=/home/mmoro/Projects/no_link_bug/target/debug/deps --extern macro_crate=/home/mmoro/Projects/no_link_bug/target/debug/deps/libmacro_crate-c0993a15f8871f25.rlib`
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.25s

My thoughts:

When rustc is invoked with --extern macro_crate=…/*.rlib, the crate is initially loaded as Unconditional. Later, when the compiler sees #[no_link] extern crate macro_crate, it attempts to downgrade it to MacrosOnly. However, maybe_resolve_crate uses cmp::max when updating the crate’s dep_kind, so the Unconditional status is retained. As a result, the crate is still linked, and functions like macro_crate::add are available, causing the build to succeed rather than produce a linker error.

[eggyal]

Appears to be a regression in 1.91.

On 1.90, I see the following:

   Compiling macro_crate v0.1.0 (/home/eggyal/projects/macro_crate)
   Compiling no_link_bug v0.1.0 (/home/eggyal/projects/no_link_bug)
error: linking with `cc` failed: exit status: 1
  |
  = note:  "cc" "-m64" "/tmp/rustcHLBM2N/symbols.o" "<8 object files omitted>" "-Wl,--as-needed" "-Wl,-Bstatic" "<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/lib/{libstd-*,libpanic_unwind-*,libobject-*,libmemchr-*,libaddr2line-*,libgimli-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libminiz_oxide-*,libadler2-*,libunwind-*,libcfg_if-*,liblibc-*,librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-L" "/tmp/rustcHLBM2N/raw-dylibs" "-B<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/bin/gcc-ld" "-fuse-ld=lld" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "<sysroot>/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "/home/eggyal/projects/no_link_bug/target/debug/deps/no_link_bug-983b28fb9f9ac056" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-nodefaultlibs"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error: undefined symbol: macro_crate::add::hfd94750f91296b71
          >>> referenced by main.rs:9 (src/main.rs:9)
          >>>               /home/eggyal/projects/no_link_bug/target/debug/deps/no_link_bug-983b28fb9f9ac056.0bmy1e9jvfw8ymnd4muh4wrs5.0pr1ina.rcgu.o:(no_link_bug::main::h7337b9e69389db87)
          collect2: error: ld returned 1 exit status
          

error: could not compile `no_link_bug` (bin "no_link_bug") due to 1 previous error

@rustbot label +A-linkage +E-needs-bisection +T-compiler +regression-from-stable-to-stable -needs-triage

[rustbot]

Error: Unknown labels: E-needs-bisect

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[bjorn3]

add was likely cross-crate inlined, so macro_crate happened to not actually be necessary at link time. In any case #[no_link] is very fragile as there are no checks that you are not using anything from such a crate other than macros. I did be in favor of deprecating and removing it.

[petrochenkov]

Please, check the linker command line to make sure that macro_crate is indeed linked.
fn add may be opportunistically inlined at MIR level because it's very small.

When rustc is invoked with --extern macro_crate=…/*.rlib, the crate is initially loaded as Unconditional

--extern by itself doesn't cause any crate loading, it only specifies where to find the crate if it's actually used.

[eggyal]

in favor of deprecating and removing it

What are the use cases for it? I can't see any RFC.

[petrochenkov]

It's a pre-Rust 1.0 attribute that was stabilized accidentally.
IIRC it was used for compiler plugins originally.

[eggyal]

I guess a crater run to guage how much removal might impact the ecosystem, and then nominate for lang discussion?