LLD doesn't handle `--warn-unresolved-symbols` the same as GNU LD

[el-yawd]

While upgrading tursodb to rust 1.90 I got this linker error on CI:

Running unittests src/lib.rs (target/debug/deps/turso_sync_js-5f98d3f835f912a1)
/home/runner/_work/turso/turso/target/debug/deps/turso_sync_js-5f98d3f835f912a1: symbol lookup error: /home/runner/_work/turso/turso/target/debug/deps/turso_sync_js-5f98d3f835f912a1: undefined symbol: napi_typeof
error: test failed, to rerun pass `-p turso_sync_js --lib`

As David pointed out, the --warn-unresolved-symbols flag is enabled and the error only happens during runtime.

Using the old linker fix the issue. I do not know how to properly debug this so any help would be appreciated :)

Version it worked on

It most recently worked on: 1.88

Version with regression

rustc --version --verbose:

rustc 1.90.0 (1159e78c4 2025-09-14)
binary: rustc
commit-hash: 1159e78c4747b02ef996e55082b704c09b970588
commit-date: 2025-09-14
host: x86_64-unknown-linux-gnu
release: 1.90.0
LLVM version: 20.1.8

@rustbot modify labels: +regression-from-stable-to-stable -regression-untriaged

[davidlattimore]

Copying part of what I wrote on the related wild issue:

I've tried linking with GNU ld, lld and wild. All three report warnings about a whole lot of undefined symbols. Normally these undefined symbols would be errors, but the flag --warn-unresolved-symbols was passed to the linker.

It seems that in the presence of undefined symbols and the --warn-unresolved-symbols flag the behaviour of the linkers differs. Wild and LLD emit dynamic relocations for the symbols with the assumption that they'll become defined at runtime. GNU ld does not.

[madsmtm]

I tried searching for uses of --warn-unresolved-symbols on GitHub, found that most usage of this comes from the NAPI issue (napi-rs/napi-rs#1782) with most builds being unaffected (only test builds hit this as IIUC), and from a single other use.

Given that, I'll mark this P-medium.

Note that tursodb and other projects that use NAPI and encounter this should be able to work around it by adding the following to .cargo/config.toml:

[target.'cfg(all(target_os = "linux", target_env = "gnu"))']
linker = "ld" # Or `-Clinker-flavor=ld`
rustflags = [ ... ]

(Similar to what they already do when specifying --warn-unresolved-symbols in the first place).