test/cctest/test-mark-compact.cc - platform/external/v8 - Git at Google

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include <stdlib.h>

 #include "v8.h"

 #include "global-handles.h"
 #include "snapshot.h"
 #include "top.h"
 #include "cctest.h"

 using namespace v8::internal;

 static v8::Persistent<v8::Context> env;

 static void InitializeVM() {
   if (env.IsEmpty()) env = v8::Context::New();
   v8::HandleScope scope;
   env->Enter();
 }


 TEST(MarkingStack) {
   int mem_size = 20 * kPointerSize;
   byte* mem = NewArray<byte>(20*kPointerSize);
   Address low = reinterpret_cast<Address>(mem);
   Address high = low + mem_size;
   MarkingStack s;
   s.Initialize(low, high);

   Address address = NULL;
   while (!s.is_full()) {
     s.Push(HeapObject::FromAddress(address));
     address += kPointerSize;
   }

   while (!s.is_empty()) {
     Address value = s.Pop()->address();
     address -= kPointerSize;
     CHECK_EQ(address, value);
   }

   CHECK_EQ(NULL, address);
   DeleteArray(mem);
 }


 TEST(Promotion) {
   // Ensure that we get a compacting collection so that objects are promoted
   // from new space.
   FLAG_gc_global = true;
   FLAG_always_compact = true;
   Heap::ConfigureHeap(2*256*KB, 4*MB);

   InitializeVM();

   v8::HandleScope sc;

   // Allocate a fixed array in the new space.
   int array_size =
       (Heap::MaxObjectSizeInPagedSpace() - FixedArray::kHeaderSize) /
       (kPointerSize * 4);
   Object* obj = Heap::AllocateFixedArray(array_size);
   CHECK(!obj->IsFailure());

   Handle<FixedArray> array(FixedArray::cast(obj));

   // Array should be in the new space.
   CHECK(Heap::InSpace(*array, NEW_SPACE));

   // Call the m-c collector, so array becomes an old object.
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   // Array now sits in the old space
   CHECK(Heap::InSpace(*array, OLD_POINTER_SPACE));
 }


 TEST(NoPromotion) {
   Heap::ConfigureHeap(2*256*KB, 4*MB);

   // Test the situation that some objects in new space are promoted to
   // the old space
   InitializeVM();

   v8::HandleScope sc;

   // Do a mark compact GC to shrink the heap.
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   // Allocate a big Fixed array in the new space.
   int size = (Heap::MaxObjectSizeInPagedSpace() - FixedArray::kHeaderSize) /
       kPointerSize;
   Object* obj = Heap::AllocateFixedArray(size);

   Handle<FixedArray> array(FixedArray::cast(obj));

   // Array still stays in the new space.
   CHECK(Heap::InSpace(*array, NEW_SPACE));

   // Allocate objects in the old space until out of memory.
   FixedArray* host = *array;
   while (true) {
     Object* obj = Heap::AllocateFixedArray(100, TENURED);
     if (obj->IsFailure()) break;

     host->set(0, obj);
     host = FixedArray::cast(obj);
   }

   // Call mark compact GC, and it should pass.
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   // array should not be promoted because the old space is full.
   CHECK(Heap::InSpace(*array, NEW_SPACE));
 }


 TEST(MarkCompactCollector) {
   InitializeVM();

   v8::HandleScope sc;
   // call mark-compact when heap is empty
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   // keep allocating garbage in new space until it fails
   const int ARRAY_SIZE = 100;
   Object* array;
   do {
     array = Heap::AllocateFixedArray(ARRAY_SIZE);
   } while (!array->IsFailure());
   CHECK(Heap::CollectGarbage(0, NEW_SPACE));

   array = Heap::AllocateFixedArray(ARRAY_SIZE);
   CHECK(!array->IsFailure());

   // keep allocating maps until it fails
   Object* mapp;
   do {
     mapp = Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
   } while (!mapp->IsFailure());
   CHECK(Heap::CollectGarbage(0, MAP_SPACE));
   mapp = Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
   CHECK(!mapp->IsFailure());

   // allocate a garbage
   String* func_name = String::cast(Heap::LookupAsciiSymbol("theFunction"));
   SharedFunctionInfo* function_share =
     SharedFunctionInfo::cast(Heap::AllocateSharedFunctionInfo(func_name));
   JSFunction* function =
     JSFunction::cast(Heap::AllocateFunction(*Top::function_map(),
                                             function_share,
                                             Heap::undefined_value()));
   Map* initial_map =
       Map::cast(Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize));
   function->set_initial_map(initial_map);
   Top::context()->global()->SetProperty(func_name, function, NONE);

   JSObject* obj = JSObject::cast(Heap::AllocateJSObject(function));
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   func_name = String::cast(Heap::LookupAsciiSymbol("theFunction"));
   CHECK(Top::context()->global()->HasLocalProperty(func_name));
   Object* func_value = Top::context()->global()->GetProperty(func_name);
   CHECK(func_value->IsJSFunction());
   function = JSFunction::cast(func_value);

   obj = JSObject::cast(Heap::AllocateJSObject(function));
   String* obj_name = String::cast(Heap::LookupAsciiSymbol("theObject"));
   Top::context()->global()->SetProperty(obj_name, obj, NONE);
   String* prop_name = String::cast(Heap::LookupAsciiSymbol("theSlot"));
   obj->SetProperty(prop_name, Smi::FromInt(23), NONE);

   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   obj_name = String::cast(Heap::LookupAsciiSymbol("theObject"));
   CHECK(Top::context()->global()->HasLocalProperty(obj_name));
   CHECK(Top::context()->global()->GetProperty(obj_name)->IsJSObject());
   obj = JSObject::cast(Top::context()->global()->GetProperty(obj_name));
   prop_name = String::cast(Heap::LookupAsciiSymbol("theSlot"));
   CHECK(obj->GetProperty(prop_name) == Smi::FromInt(23));
 }


 static Handle<Map> CreateMap() {
   return Factory::NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
 }


 TEST(MapCompact) {
   FLAG_max_map_space_pages = 16;
   InitializeVM();

   {
     v8::HandleScope sc;
     // keep allocating maps while pointers are still encodable and thus
     // mark compact is permitted.
     Handle<JSObject> root = Factory::NewJSObjectFromMap(CreateMap());
     do {
       Handle<Map> map = CreateMap();
       map->set_prototype(*root);
       root = Factory::NewJSObjectFromMap(map);
     } while (Heap::map_space()->MapPointersEncodable());
   }
   // Now, as we don't have any handles to just allocated maps, we should
   // be able to trigger map compaction.
   // To give an additional chance to fail, try to force compaction which
   // should be impossible right now.
   Heap::CollectAllGarbage(true);
   // And now map pointers should be encodable again.
   CHECK(Heap::map_space()->MapPointersEncodable());
 }


 static int gc_starts = 0;
 static int gc_ends = 0;

 static void GCPrologueCallbackFunc() {
   CHECK(gc_starts == gc_ends);
   gc_starts++;
 }


 static void GCEpilogueCallbackFunc() {
   CHECK(gc_starts == gc_ends + 1);
   gc_ends++;
 }


 TEST(GCCallback) {
   InitializeVM();

   Heap::SetGlobalGCPrologueCallback(&GCPrologueCallbackFunc);
   Heap::SetGlobalGCEpilogueCallback(&GCEpilogueCallbackFunc);

   // Scavenge does not call GC callback functions.
   Heap::PerformScavenge();

   CHECK_EQ(0, gc_starts);
   CHECK_EQ(gc_ends, gc_starts);

   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));
   CHECK_EQ(1, gc_starts);
   CHECK_EQ(gc_ends, gc_starts);
 }


 static int NumberOfWeakCalls = 0;
 static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
   NumberOfWeakCalls++;
   handle.Dispose();
 }

 TEST(ObjectGroups) {
   InitializeVM();

   NumberOfWeakCalls = 0;
   v8::HandleScope handle_scope;

   Handle<Object> g1s1 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1));
   Handle<Object> g1s2 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1));
   GlobalHandles::MakeWeak(g1s1.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
   GlobalHandles::MakeWeak(g1s2.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);

   Handle<Object> g2s1 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1));
   Handle<Object> g2s2 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1));
   GlobalHandles::MakeWeak(g2s1.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
   GlobalHandles::MakeWeak(g2s2.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);

   Handle<Object> root = GlobalHandles::Create(*g1s1);  // make a root.

   // Connect group 1 and 2, make a cycle.
   Handle<FixedArray>::cast(g1s2)->set(0, *g2s2);
   Handle<FixedArray>::cast(g2s1)->set(0, *g1s1);

   {
     Object** g1_objects[] = { g1s1.location(), g1s2.location() };
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     GlobalHandles::AddGroup(g1_objects, 2);
     GlobalHandles::AddGroup(g2_objects, 2);
   }
   // Do a full GC
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   // All object should be alive.
   CHECK_EQ(0, NumberOfWeakCalls);

   // Weaken the root.
   GlobalHandles::MakeWeak(root.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);

   // Groups are deleted, rebuild groups.
   {
     Object** g1_objects[] = { g1s1.location(), g1s2.location() };
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     GlobalHandles::AddGroup(g1_objects, 2);
     GlobalHandles::AddGroup(g2_objects, 2);
   }

   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

   // All objects should be gone. 5 global handles in total.
   CHECK_EQ(5, NumberOfWeakCalls);
 }
	// Copyright 2006-2008 the V8 project authors. All rights reserved.
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are
	// met:
	//
	// * Redistributions of source code must retain the above copyright
	// notice, this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above
	// copyright notice, this list of conditions and the following
	// disclaimer in the documentation and/or other materials provided
	// with the distribution.
	// * Neither the name of Google Inc. nor the names of its
	// contributors may be used to endorse or promote products derived
	// from this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include <stdlib.h>

	#include "v8.h"

	#include "global-handles.h"
	#include "snapshot.h"
	#include "top.h"
	#include "cctest.h"

	using namespace v8::internal;

	static v8::Persistent<v8::Context> env;

	static void InitializeVM() {
	if (env.IsEmpty()) env = v8::Context::New();
	v8::HandleScope scope;
	env->Enter();
	}


	TEST(MarkingStack) {
	int mem_size = 20 * kPointerSize;
	byte* mem = NewArray<byte>(20*kPointerSize);
	Address low = reinterpret_cast<Address>(mem);
	Address high = low + mem_size;
	MarkingStack s;
	s.Initialize(low, high);

	Address address = NULL;
	while (!s.is_full()) {
	s.Push(HeapObject::FromAddress(address));
	address += kPointerSize;
	}

	while (!s.is_empty()) {
	Address value = s.Pop()->address();
	address -= kPointerSize;
	CHECK_EQ(address, value);
	}

	CHECK_EQ(NULL, address);
	DeleteArray(mem);
	}


	TEST(Promotion) {
	// Ensure that we get a compacting collection so that objects are promoted
	// from new space.
	FLAG_gc_global = true;
	FLAG_always_compact = true;
	Heap::ConfigureHeap(2256KB, 4*MB);

	InitializeVM();

	v8::HandleScope sc;

	// Allocate a fixed array in the new space.
	int array_size =
	(Heap::MaxObjectSizeInPagedSpace() - FixedArray::kHeaderSize) /
	(kPointerSize * 4);
	Object* obj = Heap::AllocateFixedArray(array_size);
	CHECK(!obj->IsFailure());

	Handle<FixedArray> array(FixedArray::cast(obj));

	// Array should be in the new space.
	CHECK(Heap::InSpace(*array, NEW_SPACE));

	// Call the m-c collector, so array becomes an old object.
	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	// Array now sits in the old space
	CHECK(Heap::InSpace(*array, OLD_POINTER_SPACE));
	}


	TEST(NoPromotion) {
	Heap::ConfigureHeap(2256KB, 4*MB);

	// Test the situation that some objects in new space are promoted to
	// the old space
	InitializeVM();

	v8::HandleScope sc;

	// Do a mark compact GC to shrink the heap.
	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	// Allocate a big Fixed array in the new space.
	int size = (Heap::MaxObjectSizeInPagedSpace() - FixedArray::kHeaderSize) /
	kPointerSize;
	Object* obj = Heap::AllocateFixedArray(size);

	Handle<FixedArray> array(FixedArray::cast(obj));

	// Array still stays in the new space.
	CHECK(Heap::InSpace(*array, NEW_SPACE));

	// Allocate objects in the old space until out of memory.
	FixedArray* host = *array;
	while (true) {
	Object* obj = Heap::AllocateFixedArray(100, TENURED);
	if (obj->IsFailure()) break;

	host->set(0, obj);
	host = FixedArray::cast(obj);
	}

	// Call mark compact GC, and it should pass.
	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	// array should not be promoted because the old space is full.
	CHECK(Heap::InSpace(*array, NEW_SPACE));
	}


	TEST(MarkCompactCollector) {
	InitializeVM();

	v8::HandleScope sc;
	// call mark-compact when heap is empty
	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	// keep allocating garbage in new space until it fails
	const int ARRAY_SIZE = 100;
	Object* array;
	do {
	array = Heap::AllocateFixedArray(ARRAY_SIZE);
	} while (!array->IsFailure());
	CHECK(Heap::CollectGarbage(0, NEW_SPACE));

	array = Heap::AllocateFixedArray(ARRAY_SIZE);
	CHECK(!array->IsFailure());

	// keep allocating maps until it fails
	Object* mapp;
	do {
	mapp = Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
	} while (!mapp->IsFailure());
	CHECK(Heap::CollectGarbage(0, MAP_SPACE));
	mapp = Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
	CHECK(!mapp->IsFailure());

	// allocate a garbage
	String* func_name = String::cast(Heap::LookupAsciiSymbol("theFunction"));
	SharedFunctionInfo* function_share =
	SharedFunctionInfo::cast(Heap::AllocateSharedFunctionInfo(func_name));
	JSFunction* function =
	JSFunction::cast(Heap::AllocateFunction(*Top::function_map(),
	function_share,
	Heap::undefined_value()));
	Map* initial_map =
	Map::cast(Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize));
	function->set_initial_map(initial_map);
	Top::context()->global()->SetProperty(func_name, function, NONE);

	JSObject* obj = JSObject::cast(Heap::AllocateJSObject(function));
	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	func_name = String::cast(Heap::LookupAsciiSymbol("theFunction"));
	CHECK(Top::context()->global()->HasLocalProperty(func_name));
	Object* func_value = Top::context()->global()->GetProperty(func_name);
	CHECK(func_value->IsJSFunction());
	function = JSFunction::cast(func_value);

	obj = JSObject::cast(Heap::AllocateJSObject(function));
	String* obj_name = String::cast(Heap::LookupAsciiSymbol("theObject"));
	Top::context()->global()->SetProperty(obj_name, obj, NONE);
	String* prop_name = String::cast(Heap::LookupAsciiSymbol("theSlot"));
	obj->SetProperty(prop_name, Smi::FromInt(23), NONE);

	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	obj_name = String::cast(Heap::LookupAsciiSymbol("theObject"));
	CHECK(Top::context()->global()->HasLocalProperty(obj_name));
	CHECK(Top::context()->global()->GetProperty(obj_name)->IsJSObject());
	obj = JSObject::cast(Top::context()->global()->GetProperty(obj_name));
	prop_name = String::cast(Heap::LookupAsciiSymbol("theSlot"));
	CHECK(obj->GetProperty(prop_name) == Smi::FromInt(23));
	}


	static Handle<Map> CreateMap() {
	return Factory::NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
	}


	TEST(MapCompact) {
	FLAG_max_map_space_pages = 16;
	InitializeVM();

	{
	v8::HandleScope sc;
	// keep allocating maps while pointers are still encodable and thus
	// mark compact is permitted.
	Handle<JSObject> root = Factory::NewJSObjectFromMap(CreateMap());
	do {
	Handle<Map> map = CreateMap();
	map->set_prototype(*root);
	root = Factory::NewJSObjectFromMap(map);
	} while (Heap::map_space()->MapPointersEncodable());
	}
	// Now, as we don't have any handles to just allocated maps, we should
	// be able to trigger map compaction.
	// To give an additional chance to fail, try to force compaction which
	// should be impossible right now.
	Heap::CollectAllGarbage(true);
	// And now map pointers should be encodable again.
	CHECK(Heap::map_space()->MapPointersEncodable());
	}


	static int gc_starts = 0;
	static int gc_ends = 0;

	static void GCPrologueCallbackFunc() {
	CHECK(gc_starts == gc_ends);
	gc_starts++;
	}


	static void GCEpilogueCallbackFunc() {
	CHECK(gc_starts == gc_ends + 1);
	gc_ends++;
	}


	TEST(GCCallback) {
	InitializeVM();

	Heap::SetGlobalGCPrologueCallback(&GCPrologueCallbackFunc);
	Heap::SetGlobalGCEpilogueCallback(&GCEpilogueCallbackFunc);

	// Scavenge does not call GC callback functions.
	Heap::PerformScavenge();

	CHECK_EQ(0, gc_starts);
	CHECK_EQ(gc_ends, gc_starts);

	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));
	CHECK_EQ(1, gc_starts);
	CHECK_EQ(gc_ends, gc_starts);
	}


	static int NumberOfWeakCalls = 0;
	static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
	NumberOfWeakCalls++;
	handle.Dispose();
	}

	TEST(ObjectGroups) {
	InitializeVM();

	NumberOfWeakCalls = 0;
	v8::HandleScope handle_scope;

	Handle<Object> g1s1 =
	GlobalHandles::Create(Heap::AllocateFixedArray(1));
	Handle<Object> g1s2 =
	GlobalHandles::Create(Heap::AllocateFixedArray(1));
	GlobalHandles::MakeWeak(g1s1.location(),
	reinterpret_cast<void*>(1234),
	&WeakPointerCallback);
	GlobalHandles::MakeWeak(g1s2.location(),
	reinterpret_cast<void*>(1234),
	&WeakPointerCallback);

	Handle<Object> g2s1 =
	GlobalHandles::Create(Heap::AllocateFixedArray(1));
	Handle<Object> g2s2 =
	GlobalHandles::Create(Heap::AllocateFixedArray(1));
	GlobalHandles::MakeWeak(g2s1.location(),
	reinterpret_cast<void*>(1234),
	&WeakPointerCallback);
	GlobalHandles::MakeWeak(g2s2.location(),
	reinterpret_cast<void*>(1234),
	&WeakPointerCallback);

	Handle<Object> root = GlobalHandles::Create(*g1s1); // make a root.

	// Connect group 1 and 2, make a cycle.
	Handle<FixedArray>::cast(g1s2)->set(0, *g2s2);
	Handle<FixedArray>::cast(g2s1)->set(0, *g1s1);

	{
	Object** g1_objects[] = { g1s1.location(), g1s2.location() };
	Object** g2_objects[] = { g2s1.location(), g2s2.location() };
	GlobalHandles::AddGroup(g1_objects, 2);
	GlobalHandles::AddGroup(g2_objects, 2);
	}
	// Do a full GC
	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	// All object should be alive.
	CHECK_EQ(0, NumberOfWeakCalls);

	// Weaken the root.
	GlobalHandles::MakeWeak(root.location(),
	reinterpret_cast<void*>(1234),
	&WeakPointerCallback);

	// Groups are deleted, rebuild groups.
	{
	Object** g1_objects[] = { g1s1.location(), g1s2.location() };
	Object** g2_objects[] = { g2s1.location(), g2s2.location() };
	GlobalHandles::AddGroup(g1_objects, 2);
	GlobalHandles::AddGroup(g2_objects, 2);
	}

	CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));

	// All objects should be gone. 5 global handles in total.
	CHECK_EQ(5, NumberOfWeakCalls);
	}