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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