global.set: Wasm variable instruction

The global.set variable instruction sets the value of a global variable.

Try it

(module
  (import "console" "log" (func $log (param i32)))
  (global $var (mut i32) (i32.const 0))
  (func $main
    i32.const 10 ;; load a number onto the stack
    global.set $var ;; set the $var

    global.get $var ;; load $var onto the stack
    call $log ;; log the result
  )
  (start $main)
)

const url = "{%wasm-url%}";
await WebAssembly.instantiateStreaming(fetch(url), { console });

Syntax

global.set identifier

global.set

The global.set instruction type. Must always be included first.

identifier

An identifier for the global whose value you want to set. This can be one of the following:

name

The identifying name set for the global when it was first initialized. This must begin with a $ symbol, for example $my_global.

index

The global's index number, for example 0 for the first global in the Wasm script, 1 for the second, etc.

Type

[new_value] -> []

new_value

The new value set for the global. For the global.set instruction to succeed, the global must be mutable (the mut flag was set when it was declared), and the new_value must have the same data_type as the global.

Opcodes

Specifications

• WebAssembly Core Specification

See also

• global
• global.get