src/share/vm/oops/arrayOop.hpp

rev 2779 : 7102044: G1: VM crashes with assert(old_end != new_end) failed: don't call this otherwise
Summary: arrayOopDesc::max_array_length() should return a value that does not overflow a size_t if it is converted to bytes.
Reviewed-by: stefank, kvn

*** 1,7 ****
  /*
!  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
--- 1,7 ----
  /*
!  * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
*** 102,123 ****
        : typesize_in_bytes/HeapWordSize);
    }
  
    // Return the maximum length of an array of BasicType.  The length can passed
    // to typeArrayOop::object_size(scale, length, header_size) without causing an
!   // overflow.
    static int32_t max_array_length(BasicType type) {
      assert(type >= 0 && type < T_CONFLICT, "wrong type");
      assert(type2aelembytes(type) != 0, "wrong type");
!     const int bytes_per_element = type2aelembytes(type);
!     if (bytes_per_element < HeapWordSize) {
        return max_jint;
      }
! 
!     const int32_t max_words = align_size_down(max_jint, MinObjAlignment);
!     const int32_t max_element_words = max_words - header_size(type);
!     const int32_t words_per_element = bytes_per_element >> LogHeapWordSize;
!     return max_element_words / words_per_element;
    }
  };
  
  #endif // SHARE_VM_OOPS_ARRAYOOP_HPP
--- 102,129 ----
        : typesize_in_bytes/HeapWordSize);
    }
  
    // Return the maximum length of an array of BasicType.  The length can passed
    // to typeArrayOop::object_size(scale, length, header_size) without causing an
!   // overflow. We also need to make sure that this will not overflow a size_t on
!   // 32 bit platforms when we convert it to a byte size.
    static int32_t max_array_length(BasicType type) {
      assert(type >= 0 && type < T_CONFLICT, "wrong type");
      assert(type2aelembytes(type) != 0, "wrong type");
! 
!     const size_t max_words_per_size_t = align_size_down((SIZE_MAX/HeapWordSize - header_size(type)), MinObjAlignment);
!     const size_t max_elements_per_size_t = HeapWordSize * max_words_per_size_t / type2aelembytes(type);
!     if ((size_t)max_jint < max_elements_per_size_t) {
        return max_jint;
      }
!     return (int32_t)max_elements_per_size_t;
    }
+   
+ // for unit testing
+ #ifndef PRODUCT
+   static bool check_max_length_overflow(BasicType type);
+   static int32_t old_max_array_length(BasicType type);
+   static bool test_max_array_length();
+ #endif
  };
  
  #endif // SHARE_VM_OOPS_ARRAYOOP_HPP