build error: unable to find library -latomic (llvm/compiler-rt)

Version

b949c28b7957f913bfbf042e6b07a22af59f1f3f

Platform

Linux aarch64-unknown-linux-musl 7.2.3-gentoo-dist-hardened #1 SMP PREEMPT_DYNAMIC Sat Sep  5 05:15:30 CEST 2026 aarch64 GNU/Linux

llvm stack (clang, libcxx, compiler-rt, libunwind)

Subsystem

No response

What steps will reproduce the bug?

$ ./configure
$ make

How often does it reproduce? Is there a required condition?

always

What is the expected behavior? Why is that the expected behavior?

build succeeds

What do you see instead?

ld.lld: error: unable to find library -latomic
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [node_js2c.target.mk:144: /home/pepper/dev/ghrepos/node/out/Release/node_js2c] Error 1
make: *** [Makefile:145: node] Error 2

Additional information

This comment in tools/v8_gypfiles/v8.gyp suggests, that -latomic was added to facilitate the use of atomic operations as described in the linked clang docs:

# Platforms that don't have Compare-And-Swap (CAS) support need to link atomic library
# to implement atomic memory access.
# Clang needs it for some atomic operations (https://clang.llvm.org/docs/Toolchain.html#atomics-library).
 ['(OS=="linux" and clang==1) or (v8_current_cpu in ["mips64", "mips64el", "arm", "riscv64", "loong64"])', {

But the docs also state that compiler-rt (LLVM) or libatomic (GNU) may be used. -latomic requests libatomic while atomics from compiler-rt can be used without linker settings.

Current behaviour
The builds adds -latomic which unconditionally requests to link libatomic even in cases when it is not needed or desired.

Desired behaviour
Check if -latomic is needed e.g. like mesa meson.build, which checks if atomics compile successfully without link settings (which is the case with compiler-rt). Then append them conditionally only when needed.

Start with tools/v8_gypfiles/v8.gyp around the referenced atomic-library condition, then reproduce with ./configure and make on the reported Linux aarch64 musl setup. Compare the existing -latomic handling with the linked Mesa approach and verify that the node_js2c build succeeds without an unavailable library while still linking it when required.