symbol-description-atom-ref.js

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// Reading a unique symbol's description must record a reference to the

// description atom in the reading zone's atom reference bitmap, since unique

// symbols themselves are not recorded there.

gczeal(0);

let other = newGlobal({newCompartment: true});

// Create a unique symbol in the other zone and return the atom mark index of

// its description. The description itself is never returned from |other| so no

// reference to it is recorded in this zone.

function makeSymbol() {

  other.eval(`

    var sym = Symbol("description-" + Math.random());

    var descIndex = getAtomMarkIndex(sym.description);

`);

  return other.eval('descIndex');

let index = makeSymbol();

assertEq(getAtomMarkColor(other, index), 'black');

assertEq(getAtomMarkColor(this, index), 'white');

let sym = other.eval('sym');

assertEq(typeof sym, 'symbol');

// Obtaining the symbol does not reference its description.

assertEq(getAtomMarkColor(this, index), 'white');

let desc = sym.description;

assertEq(typeof desc, 'string');

assertEq(getAtomMarkColor(this, index), 'black');

// Drop all references to the symbol and check that the description survives a

// full GC, which refines the atom reference bitmaps.

other.eval('sym = undefined;');

sym = undefined;

gc();

assertEq(getAtomMarkColor(this, index), 'black');

assertEq(desc.startsWith("description-"), true);

// Same again, but only collect this zone and the atoms zone.

index = makeSymbol();

assertEq(getAtomMarkColor(this, index), 'white');

sym = other.eval('sym');

assertEq(getAtomMarkColor(this, index), 'white');

desc = sym.description;

assertEq(getAtomMarkColor(this, index), 'black');

other.eval('sym = undefined;');

sym = undefined;

schedulezone(this);

schedulezone('atoms');

gc('zone');

assertEq(getAtomMarkColor(this, index), 'black');

assertEq(desc.startsWith("description-"), true);