421 #ifndef PRODUCT

   422 // Override of memory state checking method in CollectedHeap:

   423 // Some collectors (CMS for example) can't have badHeapWordVal written

   424 // in the first two words of an object. (For instance , in the case of

   425 // CMS these words hold state used to synchronize between certain

   426 // (concurrent) GC steps and direct allocating mutators.)

   427 // The skip_header_HeapWords() method below, allows us to skip

   428 // over the requisite number of HeapWord's. Note that (for

   429 // generational collectors) this means that those many words are

   430 // skipped in each object, irrespective of the generation in which

   431 // that object lives. The resultant loss of precision seems to be

   432 // harmless and the pain of avoiding that imprecision appears somewhat

   433 // higher than we are prepared to pay for such rudimentary debugging

   434 // support.

   435 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,

   436                                                          size_t size) {

   437   if (CheckMemoryInitialization && ZapUnusedHeapArea) {

   438     // We are asked to check a size in HeapWords,

   439     // but the memory is mangled in juint words.

   440     juint* start = (juint*) (addr + skip_header_HeapWords());

   441     juint* end   = (juint*) (addr + size);

   442     for (juint* slot = start; slot < end; slot += 1) {

   443       assert(*slot == badHeapWordVal,

   444              "Found non badHeapWordValue in pre-allocation check");

   445     }

   446   }

   447 }

   448 #endif

   449