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call & call_indirect

call invokes a function by index or name. call_indirect dispatches through a table and type-checks the signature at runtime.

(module
  (type $t0 (func (param i32) (result i32)))


  (func $double (type $t0) (param $x i32) (result i32)
    (i32.mul (local.get $x) (i32.const 2)))


  (func (export "use_call") (param $n i32) (result i32)
    (call $double (local.get $n)))


  (table 1 funcref)
  (elem (i32.const 0) $double)


  (func (export "use_call_indirect") (param $n i32) (result i32)
    (call_indirect (type $t0) (local.get $n) (i32.const 0)))
)
  • For call_indirect, the last argument is the table element index. Preceding arguments are passed to the function.
  • The function at that index must match the declared (type ...), or the call traps.

Instruction Reference

Section titled “Instruction Reference”