dart2wasm fails with WebAssembly.compileStreaming: Requested length for array.new_fixed too large

[IchordeDionysos]

When compiling our real application and them trying to load the WASM file main.dart.wasm it fails with

Uncaught (in promise) CompileError: WebAssembly.compileStreaming(): Requested length 10890 for array.new_fixed too large, maximum is 10000 @+4396589

flutter doctor -v

[✓] Flutter (Channel main, 3.22.0-5.0.pre.54, on macOS 14.3 23D56 darwin-arm64, locale en-DE)
    • Flutter version 3.22.0-5.0.pre.54 on channel main at /Users/dennis/develop/bin/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 98d23f709f (15 hours ago), 2024-04-06 14:51:23 -0700
    • Engine revision 605b3f35fa
    • Dart version 3.5.0 (build 3.5.0-18.0.dev)
    • DevTools version 2.34.1

[!] Android toolchain - develop for Android devices (Android SDK version 33.0.1)
    • Android SDK at /Users/dennis/Library/Android/sdk
    ✗ cmdline-tools component is missing
      Run `path/to/sdkmanager --install "cmdline-tools;latest"`
      See https://developer.android.com/studio/command-line for more details.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.

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    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 15E204a
    • CocoaPods version 1.14.3

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[✓] Android Studio (version 2023.2)
    • Android Studio at /Users/dennis/Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
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    • Java version OpenJDK Runtime Environment (build 17.0.9+0-17.0.9b1087.7-11185874)

[✓] IntelliJ IDEA Ultimate Edition (version 2023.2.1)
    • IntelliJ at /Users/dennis/Applications/IntelliJ IDEA Ultimate.app
    • Flutter plugin version 76.3.4
    • Dart plugin version 232.9559.10

[✓] VS Code (version 1.85.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension can be installed from:
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[✓] Connected device (3 available)
    • macOS (desktop)                 • macos                 • darwin-arm64   • macOS 14.3 23D56 darwin-arm64
    • Mac Designed for iPad (desktop) • mac-designed-for-ipad • darwin         • macOS 14.3 23D56 darwin-arm64
    • Chrome (web)                    • chrome                • web-javascript • Google Chrome 123.0.6312.107

[✓] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.

dart info

If providing this information as part of reporting a bug, please review the information
below to ensure it only contains things you're comfortable posting publicly.

#### General info

- Dart 3.5.0-18.0.dev (dev) (Wed Apr 3 13:07:15 2024 -0700) on "macos_arm64"
- on macos / Version 14.3 (Build 23D56)
- locale is en-DE

#### Process info

| Memory |  CPU | Elapsed time | Command line                                                                               |
| -----: | ---: | -----------: | ------------------------------------------------------------------------------------------ |
|  27 MB | 0.0% |        10:03 | dart language-server --client-id=IntelliJ-IDEA --client-version=IU-232.9559.62 --protocol=analyzer |
|  45 MB | 0.0% |        05:20 | dart language-server --client-id=IntelliJ-IDEA --client-version=IU-232.9559.62 --protocol=analyzer |
|  35 MB | 0.0% |        17:08 | flutter_tools.snapshot daemon                                                              |
|  39 MB | 0.0% |        05:21 | flutter_tools.snapshot daemon                                                              |

Tested on Chrome 123.0.6312.107

I'd like to submit a reproducible example, though the issue comes up when building our whole Flutter Web App (with some adjustments like removing packages depending on ffi, adjusting some yield* usages).

Don't really know where to start building a reproducible example ...
If there is anything that I can do to get to the bottom of this let me know 😌

[IchordeDionysos]

These issues may be related?!
WebAssembly/gc#335
WebAssembly/gc#260

[IchordeDionysos]

This is actually easy to reproduce :D

Steps to reproduce:

1. Start with the sample Flutter application
2. Change web/index.html to

<!DOCTYPE HTML>
<html>
<head>
  <meta charset="UTF-8">
  <title>Flutter web app</title>
  <script src="flutter.js"></script>
</head>
<body>
<script>
  {{flutter_build_config}}
  _flutter.loader.load();
</script>
</body>
</html>

3. Build app with flutter build web --wasm
4. Run app with cd build/web && dhttpd '--headers=Cross-Origin-Embedder-Policy=credentialless;Cross-Origin-Opener-Policy=same-origin'

[IchordeDionysos]

Hmm fuck, I can no longer reproduce it with the example app but still with our actual application ...

[mraleph]

cc @osa1

[osa1]

@IchordeDionysos Could you provide the .wasm? I don't need the source code, just the Wasm should be enough to find where this array.new_fixed is coming from, and I can debug it from there.

[IchordeDionysos]

@osa1 here you go, couldn't upload to GitHub ...:
https://drive.google.com/file/d/1VhVETC8Jh3UK0vvIgWLqcQM-G3wPRb2E/view?usp=sharing

[osa1]

@IchordeDionysos I don't have access to the file.

[IchordeDionysos]

@osa1 ahh sorry should now work

[osa1]

@IchordeDionysos Thanks, I can access the file now but it doesn't have any symbols.. Would it be possible for you to build with flutter build web --wasm --no-strip-wasm -O1?

(I don't know why Flutter doesn't allow -O0, hopefully -O1 is enough..)

[IchordeDionysos]

@osa1 this command flutter build web --wasm --no-strip-wasm -O1 did not work for me ...
However, this worked flutter build web --wasm --no-strip-wasm (taken from the Flutter WASM docs)

I've uploaded a new file version in the file/link above

It now has those things at the end of the file:

[osa1]

Thanks. It looks like the large arrays are for _getTypeNames, _getTypeRulesSubstitutions, _getTypeRulesSupers intrinsics. We should update the Wasm array literal compiler to allocate the array lazily when it's too large:

sdk/pkg/dart2wasm/lib/constants.dart

Lines 435 to 454 in b574dab

	ConstantInfo? _makeWasmArrayLiteral(InstanceConstant constant) {
	w.ArrayType arrayType =
	translator.arrayTypeForDartType(constant.typeArguments.single);
	w.ValueType elementType = arrayType.elementType.type.unpacked;
	List<Constant> elements =
	(constant.fieldValues.values.single as ListConstant).entries;
	bool lazy = false;
	for (Constant element in elements) {
	lazy |= ensureConstant(element)?.isLazy ?? false;
	}
	return createConstant(constant, w.RefType.def(arrayType, nullable: false),
	lazy: lazy, (function, b) {
	for (Constant element in elements) {
	constants.instantiateConstant(function, b, element, elementType);
	}
	b.array_new_fixed(arrayType, elements.length);
	});
	}

I'll implement this.