test/mjsunit/stack-traces-gc.js

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// Flags: --expose-gc --allow-natives-syntax

var fired = [];
for (var i = 0; i < 100; i++) fired[i] = false;

function getter_function(i) {
  return %MarkOneShotGetter( function() { fired[i] = true; } );
}

// Error objects that die young.
for (var i = 0; i < 100; i++) {
  var error = new Error();
  // Replace the getter to observe whether it has been fired,
  // and disguise it as original getter.
  var getter = getter_function(i);
  error.__defineGetter__("stack", getter);

  error = undefined;
}

gc();
for (var i = 0; i < 100; i++) {
  assertFalse(fired[i]);
}

// Error objects that are kept alive.
var array = [];
for (var i = 0; i < 100; i++) {
  var error = new Error();
  var getter = getter_function(i);
  // Replace the getter to observe whether it has been fired,
  // and disguise it as original getter.
  error.__defineGetter__("stack", getter);

  array.push(error);
  error = undefined;
}

gc();
// We don't expect all stack traces to be formatted after only one GC.
assertTrue(fired[0]);

for (var i = 0; i < 10; i++) gc();
for (var i = 0; i < 100; i++) assertTrue(fired[i]);

// Error objects with custom stack getter.
var custom_error = new Error();
var custom_getter_fired = false;
custom_error.__defineGetter__("stack",
                              function() { custom_getter_fired = true; });
gc();
assertFalse(custom_getter_fired);

// Check that formatting caused by GC is not somehow observable.
var error;

var obj = { foo: function foo() { throw new Error(); } };

try {
  obj.foo();
} catch (e) {
  delete obj.foo;
  Object.defineProperty(obj, 'foo', {
    get: function() { assertUnreachable(); }
  });
  error = e;
}

gc();

Object.defineProperty(Array.prototype, '0', {
  get: function() { assertUnreachable(); }
});

try {
  throw new Error();
} catch (e) {
  error = e;
}

gc();

String.prototype.indexOf = function() { assertUnreachable(); };
String.prototype.lastIndexOf = function() { assertUnreachable(); };
var obj = { method: function() { throw Error(); } };
try {
  obj.method();
} catch (e) {
  error = e;
}

gc();