Error: 'await' is only allowed within async functions and at the top levels of modules.

[jrouwe]

Hello,

Between version 3.1.74 and 4.0.0 the debug build of JoltPhysics.js broke with error:

SyntaxError: /tmp/emscripten_temp_562xmtnb/jolt-physics.js: 'await' is only allowed within async functions and at the top levels of modules. (1002:18)

  1000 |
  1001 | };
> 1002 | var wasmExports = await createWasm();
       |                   ^

I think it's because of this change: #23157

I've created a minimal repro here (just run ./build.sh to trigger the error):

Repro.zip

In JoltPhysics.js you would reproduce it by running ./build.sh Debug.

I can reproduce almost the same error by downloading and building Ammo.js.

It seems to be the combination of -s MODULARIZE=1 and -s LEGACY_VM_SUPPORT=1 that causes the issue.

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.3 (a9651ff57165f5710bb09a5fe52590fd6ddb72df)

Failing command line in full:

emcc glue.o -s MODULARIZE=1 -s LEGACY_VM_SUPPORT=1 -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.js
SyntaxError: /tmp/emscripten_temp_562xmtnb/jolt-physics.js: 'await' is only allowed within async functions and at the top levels of modules. (1002:18)

  1000 |
  1001 | };
> 1002 | var wasmExports = await createWasm();
       |                   ^
  1003 | var ___wasm_call_ctors = createExportWrapper('__wasm_call_ctors', 0);
  1004 | var _fflush = createExportWrapper('fflush', 1);
  1005 | var _emscripten_stack_init = wasmExports['emscripten_stack_init']
    at constructor (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:360:19)
    at Parser.raise (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:3327:19)
    at Parser.raiseOverwrite (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:3343:17)
    at Parser.parseMaybeUnary (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:10720:14)
    at Parser.parseMaybeUnaryOrPrivate (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:10566:61)
    at Parser.parseExprOps (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:10571:23)
    at Parser.parseMaybeConditional (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:10548:23)
    at Parser.parseMaybeAssign (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:10511:21)
    at /home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:10481:39
    at Parser.allowInAnd (/home/jorrit/emsdk/upstream/emscripten/node_modules/@babel/parser/lib/index.js:12085:16) {
  code: 'BABEL_PARSE_ERROR',
  reasonCode: 'AwaitNotInAsyncContext',
  loc: Position { line: 1002, column: 18, index: 36412 },
  pos: 36412,
  syntaxPlugin: undefined
}
emcc: error: '/home/jorrit/emsdk/node/20.18.0_64bit/bin/node /home/jorrit/emsdk/upstream/emscripten/node_modules/.bin/babel /tmp/emscripten_temp_562xmtnb/jolt-physics.js -o /tmp/tmpvbgwc158babel.js --presets @babel/preset-env --config-file /tmp/tmpnezi8zirbabel_config.json' failed (returned 1)

Full link command and output with -v appended:

emcc -v glue.o -s MODULARIZE=1 -s LEGACY_VM_SUPPORT=1 -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.js
 /home/jorrit/emsdk/upstream/bin/clang --version
 /home/jorrit/emsdk/upstream/bin/wasm-ld -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm glue.o -L/home/jorrit/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -L/home/jorrit/emsdk/upstream/emscripten/src/lib -lGL-getprocaddr -lal -lhtml5 -lstubs-debug -lnoexit -lc-debug -ldlmalloc-debug -lcompiler_rt -lc++-noexcept -lc++abi-debug-noexcept -lsockets -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr /tmp/tmp6f5_zltilibemscripten_js_symbols.so --strip-debug --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=_emscripten_stack_alloc --export=__get_temp_ret --export=__set_temp_ret --export=__wasm_call_ctors --export=_emscripten_stack_restore --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=main --export-if-defined=__main_argc_argv --export-if-defined=fflush --export-table -z stack-size=65536 --no-growable-memory --initial-heap=16777216 --no-entry --stack-first --table-base=1
 /home/jorrit/emsdk/upstream/bin/llvm-objcopy /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm --remove-section=.debug* --remove-section=producers --remove-section=name
 /home/jorrit/emsdk/upstream/bin/wasm-emscripten-finalize --dyncalls-i64 --pass-arg=legalize-js-interface-exported-helpers /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm --detect-features
 /home/jorrit/emsdk/upstream/bin/wasm-emscripten-finalize --dyncalls-i64 --pass-arg=legalize-js-interface-exported-helpers /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm --detect-features
 /home/jorrit/emsdk/node/20.18.0_64bit/bin/node /home/jorrit/emsdk/upstream/emscripten/src/compiler.mjs /tmp/tmpi00fn030.json
 /home/jorrit/emsdk/upstream/bin/wasm-opt --signext-lowering --llvm-nontrapping-fptoint-lowering --llvm-memory-copy-fill-lowering /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm --mvp-features --enable-bulk-memory --enable-bulk-memory-opt --enable-call-indirect-overlong --enable-multivalue --enable-mutable-globals --enable-nontrapping-float-to-int --enable-reference-types --enable-sign-ext
 /home/jorrit/emsdk/upstream/bin/wasm-opt --signext-lowering --llvm-nontrapping-fptoint-lowering --llvm-memory-copy-fill-lowering /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm -o /mnt/c/Users/jrouw/Documents/Code/JoltPhysics.js/jolt-physics.wasm --mvp-features --enable-bulk-memory --enable-bulk-memory-opt --enable-call-indirect-overlong --enable-multivalue --enable-mutable-globals --enable-nontrapping-float-to-int --enable-reference-types --enable-sign-ext
 /home/jorrit/emsdk/node/20.18.0_64bit/bin/node /home/jorrit/emsdk/upstream/emscripten/node_modules/.bin/babel /tmp/emscripten_temp_x5ddoj62/jolt-physics.js -o /tmp/tmp43mtqh9xbabel.js --presets @babel/preset-env --config-file /tmp/tmpcu9h_z5rbabel_config.json
SyntaxError: /tmp/emscripten_temp_x5ddoj62/jolt-physics.js: 'await' is only allowed within async functions and at the top levels of modules. (1002:18)