299393 2025-09-23 14:34:19 -0700 Wasm validator disallows name imports longer than 100_000 bytes 2025-10-02 13:57:15 -0700 1 1 1 Unclassified WebKit WebAssembly WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 kustermann.martin syg syg webkit-bug-importer oldest_to_newest 2145345 0 kustermann.martin 2025-09-23 14:34:19 -0700 We have a dart2wasm compiler and noticed on some programs that JSC (command line shell) results in a validation error. The root cause of it is that it refuses import names longer than 100_000 bytes. Normally imported names are surely short. Though the recent js-string-builtin wasm spec enables a magic import mechanism where one can import JS strings via specially recognized imports. (Although JSC may(?) not support js-string-builtins yet, it can be polyfilled on the JS side) String constants in Dart applications can exceed 100_000 bytes and cause a wasm validation error. The root cause is due to using of the constant in [0] when decoding import names. [0] https://github.com/WebKit/WebKit/blob/68dbd317f3d24b03f06a82b11fddd2bb6e7a33b5/Source/JavaScriptCore/wasm/WasmLimits.h#L54 Expected results: Looking through the core wasm spec and js-wasm spec (https://webassembly.github.io/spec/js-api/index.html#limits) it's unclear where this 100_000 byte limit comes from. Can it be that this is not specified? D8/Chrome doesn't have this issue: It loads & runs such modules just fine. 2147293 1 webkit-bug-importer 2025-09-30 14:35:56 -0700 <rdar://problem/161683448> 2147294 2 webkit-bug-importer 2025-09-30 14:35:56 -0700 <rdar://problem/161683389> 2147861 3 syg 2025-10-02 10:03:59 -0700 Going by the git blame it seems like these limits were copied from V8 for compat reasons during the early days of Wasm. Indeed the constant still exists in V8 [1] but it seems like it was never (?) used. We'll investigate removing this limit. [1] https://source.chromium.org/chromium/chromium/src/+/main:v8/src/wasm/wasm-limits.h;l=49;drc=d78d6f646dee0f68dcc59eed2d7de0f910e2fe2a 2147874 4 syg 2025-10-02 10:50:06 -0700 Pull request: https://github.com/WebKit/WebKit/pull/51687 2147930 5 ews-feeder 2025-10-02 13:57:13 -0700 Committed 300897@main (81ff731cd920): <https://commits.webkit.org/300897@main> Reviewed commits have been landed. Closing PR #51687 and removing active labels.