Builds with Emscripten upstream are broken

[dcodeIO]

In WebAssembly/binaryen#2464 Binaryen moved from a bash script to cmake for building, and now expects Emscripten upstream (latest=1.39.3 at the time of this writing). However, after updating the buildbot stuff started breaking with an assertion being hit when trying to require the compiled binaryen.js:

• Travis/Xenial with Emsdk/latest
• Travis/Bionic with Emsdk/latest
• Travis/Xenial with Docker/trzeci/emscripten-upstream
• Travis/Bionic with Docker/trzeci/emscripten-upstream
• GitHub Actions/ubuntu-latest with Emsdk/latest

AssertionError [ERR_ASSERTION]: Got unwanted exception.
Actual message: "abort(Assertion failed: *currp, at: /home/runner/work/binaryen.js/binaryen.js/binaryen/src/wasm-traversal.h,651,pushTask). Build with -s ASSERTIONS=1 for more info."

• GitHub Actions/ubuntu-latest with Emsdk/1.39.2

AssertionError [ERR_ASSERTION]: Got unwanted exception.
Actual message: "abort(Assertion failed: s, at: /home/runner/work/binaryen.js/binaryen.js/binaryen/src/emscripten-optimizer/istring.h,65,IString). Build with -s ASSERTIONS=1 for more info."

• GitHub Actions/ubuntu-latest with Emsdk/1.39.1 (not even compiling)

[  2%] Building CXX object src/wasm/CMakeFiles/wasm.dir/literal.cpp.o
shared:WARNING: ignoring -fPIC flag when not building with SIDE_MODULE or MAIN_MODULE
shared:ERROR: treating warnings as errors (-Werror)

with the issue not being reproducible with -DCMAKE_BUILD_TYPE=Debug or locally (Debian in WSL, plain Win10 with ninja).

Also seeing the following warning in most of these setups, don't know if relevant:

CMake Warning (dev) at CMakeLists.txt:225 (ADD_LIBRARY):
  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.

Also tried switching make with ninja without success.

• Full log on GitHub Actions with Emsdk/latest

Any ideas?

[dcodeIO]

The error has changed meanwhile to

UNREACHABLE executed at /home/runner/work/binaryen.js/binaryen.js/binaryen/src/passes/DataFlowOpts.cpp:249!
undefined
Error: abort(undefined). Build with -s ASSERTIONS=1 for more info.
    at p (/home/runner/work/binaryen.js/binaryen.js/index.js:58:105)

DataFlowOpts.cpp:249

[dcodeIO]

This problem seems to be resolved now thanks to @kripken, see the issue linked above for the details. Just verified with Emscripten tip of tree and switched the bot to use tot by default, but keeping it build and test with latest and latest-fastcomp for reference.