SECURITY WARNING: Never run commands you don't understand. Always review code before execution. Use at your own risk.
FixMyError.net
WebAssembly 7 errors

WebAssembly Errors

Compile errors, memory bounds and host binding mismatches.

Understanding WebAssembly errors

WebAssembly errors are precise about the layer that failed. A CompileError means the bytes are not a valid module: most often the file was served with the wrong MIME type, or an HTML error page was fetched instead of the .wasm file. A RuntimeError: memory access out of bounds means the module read or wrote outside its linear memory, which in a language like C or Rust is a genuine memory-safety bug caught by the sandbox.

How to debug WebAssembly errors

  1. Check what the server actually returned. The wasm file must be served as application/wasm for streaming compilation, and a 404 HTML page produces a misleading magic-number error.
  2. Validate the module offline with wasm-validate and inspect it with wasm-objdump -x from the WABT toolkit.
  3. For out-of-bounds errors, rebuild with sanitizers or debug assertions in the source language. The wasm runtime cannot tell you which source line was responsible without DWARF info.
  4. Confirm imports match: every function the module imports must be supplied by the host with the exact name and signature, or instantiation fails.
  5. Build with debug symbols and use the browser's DWARF support to step through original source rather than raw wasm.

Tools worth reaching for

  • wasm-validate / wasm-objdump (WABT)
  • browser DWARF debugging
  • wasmtime --invoke
  • curl -I (check MIME type)

All 7 WebAssembly errors

Other categories