1. WebAssembly
  2. Reference
  3. WebAssembly control flow instructions
  4. unreachable

unreachable

unreachable is used to denote a point in code that should not be reachable. unreachable is an unconditional trap: in the case where an unreachable is reached and executed, the instruction traps.

Try it

(module (func (export "throw") unreachable ) ) 
const url = "{%wasm-url%}"; await WebAssembly.instantiateStreaming(fetch(url)).then((result) => { result.instance.exports.throw(); // Expected output: RuntimeError: unreachable });

Syntax

wat
unreachable
Instruction Binary opcode
unreachable 0x00

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