[WebAssembly] wasm-ld assertion failure on isa<UndefinedData>(sym)

[kripken]

wasm-ld: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/lld/wasm/SyntheticSections.cpp:522: virtual void lld::wasm::GlobalSection::writeBody(): Assertion `isa<UndefinedData>(sym)' failed.

More context and details here, including steps to reproduce:

emscripten-core/emscripten#22008 (comment)

As mentioned there this is a regression, and bisection leads to it likely caused by one of these:

   2024-01-20 sbc@chromium.org [lld][WebAssembly] Fix regression in function signature checking (#78831)
    2024-01-20 sbc@chromium.org [lld][WebAssembly] Match the ELF linker in transitioning away from archive indexes. (#78658)
    2024-01-19 sbc@chromium.org [lld][WebAssembly] Use the archive offset with --whole-archive (#78791)
    2024-01-19 sbc@chromium.org [lld][WebAssembly] Reset context object after each link (#78770)
    2024-01-19 sbc@chromium.org [lld][ELF] Simplify handleLibcall. NFC (#78659)

I'll also email @sbc100 with the output of -Wl,--reproduce as requested (too big to attach here).

[llvmbot]

@llvm/issue-subscribers-lld-wasm

Author: Alon Zakai (kripken)

``` wasm-ld: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/lld/wasm/SyntheticSections.cpp:522: virtual void lld::wasm::GlobalSection::writeBody(): Assertion `isa<UndefinedData>(sym)' failed. ```

More context and details here, including steps to reproduce:

emscripten-core/emscripten#22008 (comment)

As mentioned there this is a regression, and bisection leads to it likely caused by one of these:

   2024-01-20 sbc@<!-- -->chromium.org [lld][WebAssembly] Fix regression in function signature checking (#<!-- -->78831)
    2024-01-20 sbc@<!-- -->chromium.org [lld][WebAssembly] Match the ELF linker in transitioning away from archive indexes. (#<!-- -->78658)
    2024-01-19 sbc@<!-- -->chromium.org [lld][WebAssembly] Use the archive offset with --whole-archive (#<!-- -->78791)
    2024-01-19 sbc@<!-- -->chromium.org [lld][WebAssembly] Reset context object after each link (#<!-- -->78770)
    2024-01-19 sbc@<!-- -->chromium.org [lld][ELF] Simplify handleLibcall. NFC (#<!-- -->78659)

I'll also email @sbc100 with the output of -Wl,--reproduce as requested (too big to attach here).

[sbc100]

Am I correct in understanding that this is an LTO-only bug?

[kripken]

Hmm, I don't see any LTO involvement here. All the object files are wasm object files, and I don't see -flto in the final link command. But maybe I'm missing something, where do you see LTO?