Strengthen a few assertions and add zapping of allocated...

src/spaces.h

 // 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
@@ skipping 420 matching lines @@
   // greater than zero.
   static Page* CommitPages(Address start, size_t size, PagedSpace* owner,
                            int* num_pages);
 
   // Commit a contiguous block of memory from the initial chunk.  Assumes that
   // the address is not NULL, the size is greater than zero, and that the
   // block is contained in the initial chunk.  Returns true if it succeeded
   // and false otherwise.
   static bool CommitBlock(Address start, size_t size, Executability executable);
 
-
   // Uncommit a contiguous block of memory [start..(start+size)[.
   // start is not NULL, the size is greater than zero, and the
   // block is contained in the initial chunk.  Returns true if it succeeded
   // and false otherwise.
   static bool UncommitBlock(Address start, size_t size);
 
+  // Zaps a contiguous block of memory [start..(start+size)[ thus
+  // filling it up with a recognizable non-NULL bit pattern.
+  static void ZapBlock(Address start, size_t size);
+
   // Attempts to allocate the requested (non-zero) number of pages from the
   // OS.  Fewer pages might be allocated than requested. If it fails to
   // allocate memory for the OS or cannot allocate a single page, this
   // function returns an invalid page pointer (NULL). The caller must check
   // whether the returned page is valid (by calling Page::is_valid()).  It is
   // guaranteed that allocated pages have contiguous addresses.  The actual
   // number of allocated pages is returned in the output parameter
   // allocated_pages.  If the PagedSpace owner is executable and there is
   // a code range, the pages are allocated from the code range.
   static Page* AllocatePages(int requested_pages, int* allocated_pages,
@@ skipping 1609 matching lines @@
 
  private:
   LargeObjectChunk* current_;
   HeapObjectCallback size_func_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_