More robust when allocation fails during compaction

src/heap/spaces.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/bits.h"
 #include "src/base/platform/platform.h"
 #include "src/full-codegen.h"
 #include "src/heap/mark-compact.h"
@@ skipping 1146 matching lines @@
   Page* page = static_cast<Page*>(emergency_memory_);
   DCHECK(page->LiveBytes() == 0);
   DCHECK(AreaSize() == page->area_size());
   DCHECK(!free_list_.ContainsPageFreeListItems(page));
   heap()->isolate()->memory_allocator()->Free(page);
   emergency_memory_ = NULL;
 }
 
 
 void PagedSpace::UseEmergencyMemory() {
+  // Page::Initialize makes the chunk into a real page and adds it to the
+  // accounting for this space.  Unlike PagedSpace::Expand, we don't check
+  // CanExpand first, so we can go over the limits a little here.  That's OK,
+  // because we are in the process of compacting which will free up at least as
+  // much memory as it allocates.
   Page* page = Page::Initialize(heap(), emergency_memory_, executable(), this);
   page->InsertAfter(anchor_.prev_page());
   emergency_memory_ = NULL;
 }
 
 
 #ifdef DEBUG
 void PagedSpace::Print() {}
 #endif
 
@@ skipping 1965 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }
 }  // namespace v8::internal