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wasmrun verify

Validate a WebAssembly binary's format, structure, and integrity.

Synopsis​

wasmrun verify [WASM_FILE] [OPTIONS]

Description​

The verify command checks whether a .wasm file is a valid WebAssembly module. It validates the magic number, version, section structure, and internal consistency. Use it to catch corrupted files, incorrect compilation output, or incompatible WASM versions before execution.

Options​

-p, --path <PATH>​

Path to the WASM file.

wasmrun verify --path ./output.wasm
wasmrun verify -p ./output.wasm

Positional argument also works:

wasmrun verify ./output.wasm

-d, --detailed​

Show detailed information about the module structure.

wasmrun verify ./output.wasm --detailed

Without --detailed, verify outputs a simple pass/fail. With it, you get:

  • File size
  • Section count and sizes
  • Export names and types
  • Memory limits
  • Start function (if any)
  • Function count

Examples​

Quick Validation​

wasmrun verify ./output.wasm

Output on success:

✅ Valid WebAssembly module: output.wasm
   Size: 45,230 bytes
   Sections: 8
   Exports: 3

Output on failure:

❌ Invalid WebAssembly module: output.wasm
   Error: Invalid magic number
   Expected: \0asm (0x00 0x61 0x73 0x6D)

Detailed Verification​

wasmrun verify ./output.wasm --detailed
✅ Valid WebAssembly module: output.wasm

📊 Module Details:
   File size:     45,230 bytes
   Sections:      8
   Functions:     12
   Memory:        1 page initial, 256 pages max
   Start function: None

📦 Sections:
   Type     (1):    128 bytes
   Import   (2):    256 bytes
   Function (3):     48 bytes
   Memory   (5):      6 bytes
   Export   (7):    192 bytes
   Code     (10): 42,800 bytes
   Data     (11):  1,600 bytes

📤 Exports:
   _start    (function)
   memory    (memory)
   alloc     (function)

Pre-Deployment Check​

#!/bin/bash
if wasmrun verify ./dist/app.wasm --detailed; then
    echo "✅ Deploying..."
    deploy ./dist/app.wasm
else
    echo "❌ Verification failed, aborting deployment"
    exit 1
fi

After Compilation​

wasmrun compile ./my-project --output ./dist
wasmrun verify ./dist/output.wasm --detailed

Batch Verification​

for f in ./dist/*.wasm; do
    echo "Verifying: $f"
    wasmrun verify "$f" || echo "FAILED: $f"
done

Common Errors​

Invalid Magic Number​

❌ Invalid magic number
   Expected: \0asm (0x00 0x61 0x73 0x6D)

The file is not a WASM binary. It may be a text file, wrong format, or corrupted download.

Invalid Version​

❌ Invalid WebAssembly version
   Expected: 1 (0x01 0x00 0x00 0x00)

The file uses an unsupported WASM version. Recompile with a standard toolchain.

Malformed Section​

❌ Malformed section at offset 0x1234
   Section: Function
   Issue: Size mismatch

The binary is corrupted or was generated by a buggy compiler. Recompile from source.

See Also​

  • inspect — deeper analysis of module internals
  • compile — compile projects to WASM
  • run — compile and serve