src/share/vm/runtime/os.cpp

rev 12652 : 8168542: os::realloc should return a valid pointer for input size=0
Reviewed-by: dholmes, cjplummer, dsamersoff, rehn

*** 647,656 ****
--- 647,662 ----
    // For the test flag -XX:MallocMaxTestWords
    if (has_reached_max_malloc_test_peak(size)) {
      return NULL;
    }
  
+   if (size == 0) {
+     // return a valid pointer if size is zero
+     // if NULL is returned the calling functions assume out of memory.
+     size = 1;
+   }
+ 
  #ifndef ASSERT
    NOT_PRODUCT(inc_stat_counter(&num_mallocs, 1));
    NOT_PRODUCT(inc_stat_counter(&alloc_bytes, size));
     // NMT support
    void* membase = MemTracker::record_free(memblock);
*** 667,679 ****
      breakpoint();
    }
    // NMT support
    void* membase = MemTracker::malloc_base(memblock);
    verify_memory(membase);
-   if (size == 0) {
-     return NULL;
-   }
    // always move the block
    void* ptr = os::malloc(size, memflags, stack);
    if (PrintMalloc && tty != NULL) {
      tty->print_cr("os::realloc " SIZE_FORMAT " bytes, " PTR_FORMAT " --> " PTR_FORMAT, size, p2i(memblock), p2i(ptr));
    }
--- 673,682 ----