ref-global.js - mozsearch

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// Basic private-to-module functionality.  At the moment all we have is null

// pointers, not very exciting.

    let bin = wasmTextToBinary(

        `(module

          (type $point (struct

                        (field $x f64)

                        (field $y f64)))

          (global $g1 (mut (ref null $point)) (ref.null $point))

          (global $g2 (mut (ref null $point)) (ref.null $point))

          (global $g3 (ref null $point) (ref.null $point))

          ;; Restriction: cannot expose Refs outside the module, not even

          ;; as a return value.  See ref-restrict.js.

          (func (export "get") (result eqref)

           (global.get $g1))

          (func (export "copy")

           (global.set $g2 (global.get $g1)))

          (func (export "clear")

           (global.set $g1 (global.get $g3))

           (global.set $g2 (ref.null $point))))`);

    let mod = new WebAssembly.Module(bin);

    let ins = new WebAssembly.Instance(mod).exports;

    assertEq(ins.get(), null);

    ins.copy();                 // Should not crash

    ins.clear();                // Should not crash

// Global with struct type

    let bin = wasmTextToBinary(

        `(module

          (type $point (struct

                        (field $x f64)

                        (field $y f64)))

          (global $glob (mut (ref null $point)) (ref.null $point))

          (func (export "init")

           (global.set $glob (struct.new $point (f64.const 0.5) (f64.const 2.75))))

          (func (export "change")

           (global.set $glob (struct.new $point (f64.const 3.5) (f64.const 37.25))))

          (func (export "clear")

           (global.set $glob (ref.null $point)))

          (func (export "x") (result f64)

           (struct.get $point 0 (global.get $glob)))

          (func (export "y") (result f64)

           (struct.get $point 1 (global.get $glob))))`);

    let mod = new WebAssembly.Module(bin);

    let ins = new WebAssembly.Instance(mod).exports;

    assertErrorMessage(() => ins.x(), WebAssembly.RuntimeError, /dereferencing null pointer/);

    ins.init();

    assertEq(ins.x(), 0.5);

    assertEq(ins.y(), 2.75);

    ins.change();

    assertEq(ins.x(), 3.5);

    assertEq(ins.y(), 37.25);

    ins.clear();

    assertErrorMessage(() => ins.x(), WebAssembly.RuntimeError, /dereferencing null pointer/);

// Global value of type externref for initializer from a WebAssembly.Global,

// just check that it works.

    let bin = wasmTextToBinary(

        `(module

          (import "" "g" (global $g externref))

          (global $glob externref (global.get $g))

          (func (export "get") (result externref)

           (global.get $glob)))`);

    let mod = new WebAssembly.Module(bin);

    let obj = {zappa:37};

    let g = new WebAssembly.Global({value: "externref"}, obj);

    let ins = new WebAssembly.Instance(mod, {"":{g}}).exports;

    assertEq(ins.get(), obj);