Postpone counters triggered during GC, and use a HandleScope when calling back.

test/cctest/test-heap.cc

 // Copyright 2012 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
@@ skipping 3185 matching lines @@
   // OS so that other processes can seize the memory.  If we get a failure here
   // where there are 2 pages left instead of 1, then we should increase the
   // size of the first page a little in SizeOfFirstPage in spaces.cc.  The
   // first page should be small in order to reduce memory used when the VM
   // boots, but if the 20 small arrays don't fit on the first page then that's
   // an indication that it is too small.
   heap->CollectAllAvailableGarbage("triggered really hard");
   CHECK_EQ(1, old_space->CountTotalPages());
 }
 
+static int forced_gc_counter = 0;
+
+void MockUseCounterCallback(v8::Isolate* isolate,
+                            v8::Isolate::UseCounterFeature feature) {
+  isolate->GetCallingContext();
+  if (feature == v8::Isolate::kForcedGC) {
+    forced_gc_counter++;
+  }
+}
+
+
+TEST(CountForcedGC) {
+  i::FLAG_expose_gc = true;
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  isolate->SetUseCounterCallback(MockUseCounterCallback);
+
+  forced_gc_counter = 0;
+  const char* source = "gc();";
+  CompileRun(source);
+  CHECK_GT(forced_gc_counter, 0);

[Jakob Kummerow, 2015/05/11 08:27:37]

Why so conservative? Can this ever be != 1, and still be working as intended?

[Erik Corry, 2015/05/11 09:56:12]

An emergency out-of-memory GC is also implemented as 2-7 forced GCs.  They are
forced in the sense that they have to happen now, and can't be incremental.  So
the system does generate its own forced GCs, albeit rarely.

+}
+
 
 TEST(Regress2237) {
   i::FLAG_stress_compaction = false;
   CcTest::InitializeVM();
   Isolate* isolate = CcTest::i_isolate();
   Factory* factory = isolate->factory();
   v8::HandleScope scope(CcTest::isolate());
   Handle<String> slice(CcTest::heap()->empty_string());
 
   {
@@ skipping 2182 matching lines @@
   CHECK(pos->IsSmi());
 
   Handle<JSArray> stack_trace_array = Handle<JSArray>::cast(stack_trace);
   int array_length = Smi::cast(stack_trace_array->length())->value();
   for (int i = 0; i < array_length; i++) {
     Handle<Object> element =
         Object::GetElement(isolate, stack_trace, i).ToHandleChecked();
     CHECK(!element->IsCode());
   }
 }