[dirkwa]

[3.0.0-alpha.5] - 2025-12-03

Investigated - C#/.NET WASM Support

Status: NOT CURRENTLY WORKING

Attempted to add C#/.NET as a third WASM plugin language option using componentize-dotnet. After extensive investigation, discovered fundamental incompatibility between componentize-dotnet and Node.js/V8 (via jco transpilation).

What Was Tested:

• .NET 10.0 Preview with BytecodeAlliance.Componentize.DotNet.Wasm.SDK 0.7.0-preview00010
• WASI Component Model (P2) compilation target
• jco 1.10.0 for JavaScript transpilation

What Works:

• Building .NET WASI Component: ✅
• Transpiling with jco to JavaScript: ✅
• Plugin initialization ($init): ✅
• Plugin registration in Signal K: ✅

What Fails:

• Calling any exported function results in: RuntimeError: null function or function signature mismatch
• Root cause: .NET NativeAOT uses indirect call tables (call_indirect) that are initialized by _initialize(). This works in Wasmtime but table entries remain null in V8.

Workarounds Attempted (None Successful):

1. Manual _initialize() call - No effect
2. Manual InitializeModules() call - Crashes (already called by _initialize)
3. Various jco flags (--instantiation sync, --tla-compat) - No effect
4. Removing [ThreadStatic] attribute - Fixed build issues but not runtime

Conclusion:
componentize-dotnet explicitly only supports Wasmtime and WAMR runtimes, not V8/JavaScript. This is a known limitation documented in their README. The issue is deeply embedded in how .NET NativeAOT-LLVM structures WASM output.

Issue Filed:
bytecodealliance/componentize-dotnet#103

Files Created:

• examples/wasm-plugins/anchor-watch-dotnet/ - Complete example with documentation
• examples/wasm-plugins/anchor-watch-dotnet/ISSUE_REPORT.md - Detailed technical report

Documentation Updated:

• wasm/WASM_PLUGIN_DEV_GUIDE.md - C#/.NET section marked as NOT WORKING
• examples/wasm-plugins/anchor-watch-dotnet/README.md - Marked as NOT WORKING with explanation

Future Possibilities:

• Wait for componentize-dotnet to add V8/jco support
• Alternative: Mono interpreter approach (different compilation strategy)
• Alternative: Direct Wasmtime embedding in Node.js (if/when available)