[Pkg-javascript-devel] Bug#975069: Bug#975069: emscripten: Incompatibilities with LLVM 11

[Jonas Smedegaard]

Quoting Sébastien Jodogne (2020-11-18 20:49:27)
> >> When building a large C++ project using the current package, the
> >> WebAssembly linking might fail with error "emscripten:ERROR: emscript:
> >> failure to parse metadata output from wasm-emscripten-finalize".
> > 
> > Which exact options passed to wasm-emscripten-finalize?
> 
> After inspection of "/usr/share/emscripten/emscripten.py", the options are:
> 
> ['--detect-features', '--minimize-wasm-changes', '--dyncalls-i64',
> '--global-base=1024']
> 
> You'll find the error log attached to this mail.
> 
> Note how "wasm-emscripten-finalize" produced an invalid JSON file: It
> contains percents that are not properly escaped. From what I see on a
> working emsdk deployment, no function starting with "__invoke" in the
> "declares" section should be present.

Seems the problem is not which options emscripten passes to llvm, but 
that llvm and binaryen are out of sync: Some renaming of "emscripten EH 
EH functions" was previously done by binaryen and more recently in LLVM 
- binaryen 98 is too new to do it and LLVM is too old to do it: 
https://github.com/llvm/llvm-project/commit/3bba91f64eef15956f589fa446c265a714cc7893

Here is a minimal code to reproduce that (final parts of) that same 
error message (tested in a clean chroot of Debian sid as of today):

  apt install emscripten
  emcc --version
  /usr/share/emscripten/tests/runner.py test_exceptions


 - Jonas

-- 
 * Jonas Smedegaard - idealist & Internet-arkitekt
 * Tlf.: +45 40843136  Website: http://dr.jones.dk/

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