src/hotspot/share/memory/allocation.hpp

/*
 * Copyright (c) 1997, 2023, 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.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_MEMORY_ALLOCATION_HPP
#define SHARE_MEMORY_ALLOCATION_HPP

#include "memory/allStatic.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/macros.hpp"

#include <new>

class outputStream;
class Thread;
class JavaThread;

class AllocFailStrategy {
public:
  enum AllocFailEnum { EXIT_OOM, RETURN_NULL };
};
typedef AllocFailStrategy::AllocFailEnum AllocFailType;

// The virtual machine must never call one of the implicitly declared
// global allocation or deletion functions.  (Such calls may result in
// link-time or run-time errors.)  For convenience and documentation of
// intended use, classes in the virtual machine may be derived from one
// of the following allocation classes, some of which define allocation
// and deletion functions.
// Note: std::malloc and std::free should never called directly.

//
// For objects allocated in the resource area (see resourceArea.hpp).
// - ResourceObj
//
// For objects allocated in the C-heap (managed by: free & malloc and tracked with NMT)
// - CHeapObj
//
// For objects allocated on the stack.
// - StackObj
//
// For classes used as name spaces.
// - AllStatic
//
// For classes in Metaspace (class data)
// - MetaspaceObj
//
// The printable subclasses are used for debugging and define virtual
// member functions for printing. Classes that avoid allocating the
// vtbl entries in the objects should therefore not be the printable
// subclasses.
//
// The following macros and function should be used to allocate memory
// directly in the resource area or in the C-heap, The _OBJ variants
// of the NEW/FREE_C_HEAP macros are used for alloc/dealloc simple
// objects which are not inherited from CHeapObj, note constructor and
// destructor are not called. The preferable way to allocate objects
// is using the new operator.
//
// WARNING: The array variant must only be used for a homogeneous array
// where all objects are of the exact type specified. If subtypes are
// stored in the array then must pay attention to calling destructors
// at needed.
//
// NEW_RESOURCE_ARRAY*
// REALLOC_RESOURCE_ARRAY*
// FREE_RESOURCE_ARRAY*
// NEW_RESOURCE_OBJ*
// NEW_C_HEAP_ARRAY*
// REALLOC_C_HEAP_ARRAY*
// FREE_C_HEAP_ARRAY*
// NEW_C_HEAP_OBJ*
// FREE_C_HEAP_OBJ
//
// char* AllocateHeap(size_t size, MEMFLAGS flags, const NativeCallStack& stack, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
// char* AllocateHeap(size_t size, MEMFLAGS flags, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
// char* ReallocateHeap(char *old, size_t size, MEMFLAGS flag, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
// void FreeHeap(void* p);
//

#define MEMORY_TYPES_DO(f)                                                           \
  /* Memory type by sub systems. It occupies lower byte. */                          \
  f(mtJavaHeap,       "Java Heap")   /* Java heap                                 */ \
  f(mtClass,          "Class")       /* Java classes                              */ \
  f(mtThread,         "Thread")      /* thread objects                            */ \
  f(mtThreadStack,    "Thread Stack")                                                \
  f(mtCode,           "Code")        /* generated code                            */ \
  f(mtGC,             "GC")                                                          \
  f(mtGCCardSet,      "GCCardSet")   /* G1 card set remembered set                */ \
  f(mtCompiler,       "Compiler")                                                    \
  f(mtJVMCI,          "JVMCI")                                                       \
  f(mtInternal,       "Internal")    /* memory used by VM, but does not belong to */ \
                                     /* any of above categories, and not used by  */ \
                                     /* NMT                                       */ \
  f(mtOther,          "Other")       /* memory not used by VM                     */ \
  f(mtSymbol,         "Symbol")                                                      \
  f(mtNMT,            "Native Memory Tracking")  /* memory used by NMT            */ \
  f(mtClassShared,    "Shared class space")      /* class data sharing            */ \
  f(mtChunk,          "Arena Chunk") /* chunk that holds content of arenas        */ \
  f(mtTest,           "Test")        /* Test type for verifying NMT               */ \
  f(mtTracing,        "Tracing")                                                     \
  f(mtLogging,        "Logging")                                                     \
  f(mtStatistics,     "Statistics")                                                  \
  f(mtArguments,      "Arguments")                                                   \
  f(mtModule,         "Module")                                                      \
  f(mtSafepoint,      "Safepoint")                                                   \
  f(mtSynchronizer,   "Synchronization")                                             \
  f(mtServiceability, "Serviceability")                                              \
  f(mtMetaspace,      "Metaspace")                                                   \
  f(mtStringDedup,    "String Deduplication")                                        \
  f(mtObjectMonitor,  "Object Monitors")                                             \
  f(mtNone,           "Unknown")                                                     \
  //end

#define MEMORY_TYPE_DECLARE_ENUM(type, human_readable) \
  type,

/*
 * Memory types
 */
enum class MEMFLAGS : uint8_t  {
  MEMORY_TYPES_DO(MEMORY_TYPE_DECLARE_ENUM)
  mt_number_of_types   // number of memory types (mtDontTrack
                       // is not included as validate type)
};
// Extra insurance that MEMFLAGS truly has the same size as uint8_t.
STATIC_ASSERT(sizeof(MEMFLAGS) == sizeof(uint8_t));

#define MEMORY_TYPE_SHORTNAME(type, human_readable) \
  constexpr MEMFLAGS type = MEMFLAGS::type;

// Generate short aliases for the enum values. E.g. mtGC instead of MEMFLAGS::mtGC.
MEMORY_TYPES_DO(MEMORY_TYPE_SHORTNAME)

// Make an int version of the sentinel end value.
constexpr int mt_number_of_types = static_cast<int>(MEMFLAGS::mt_number_of_types);

extern bool NMT_track_callsite;

class NativeCallStack;


char* AllocateHeap(size_t size,
                   MEMFLAGS flags,
                   const NativeCallStack& stack,
                   AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
char* AllocateHeap(size_t size,
                   MEMFLAGS flags,
                   AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);

char* ReallocateHeap(char *old,
                     size_t size,
                     MEMFLAGS flag,
                     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);

// handles null pointers
void FreeHeap(void* p);

class CHeapObjBase {
 public:
  ALWAYSINLINE void* operator new(size_t size, MEMFLAGS f) {
    return AllocateHeap(size, f);
  }

  ALWAYSINLINE void* operator new(size_t size,
                                  MEMFLAGS f,
                                  const NativeCallStack& stack) {
    return AllocateHeap(size, f, stack);
  }

  ALWAYSINLINE void* operator new(size_t size,
                                  MEMFLAGS f,
                                  const std::nothrow_t&,
                                  const NativeCallStack& stack) throw() {
    return AllocateHeap(size, f, stack, AllocFailStrategy::RETURN_NULL);
  }

  ALWAYSINLINE void* operator new(size_t size,
                                  MEMFLAGS f,
                                  const std::nothrow_t&) throw() {
    return AllocateHeap(size, f, AllocFailStrategy::RETURN_NULL);
  }

  ALWAYSINLINE void* operator new[](size_t size, MEMFLAGS f) {
    return AllocateHeap(size, f);
  }

  ALWAYSINLINE void* operator new[](size_t size,
                                    MEMFLAGS f,
                                    const NativeCallStack& stack) {
    return AllocateHeap(size, f, stack);
  }

  ALWAYSINLINE void* operator new[](size_t size,
                                    MEMFLAGS f,
                                    const std::nothrow_t&,
                                    const NativeCallStack& stack) throw() {
    return AllocateHeap(size, f, stack, AllocFailStrategy::RETURN_NULL);
  }

  ALWAYSINLINE void* operator new[](size_t size,
                                    MEMFLAGS f,
                                    const std::nothrow_t&) throw() {
    return AllocateHeap(size, f, AllocFailStrategy::RETURN_NULL);
  }

  void operator delete(void* p)     { FreeHeap(p); }
  void operator delete [] (void* p) { FreeHeap(p); }
};

// Uses the implicitly static new and delete operators of CHeapObjBase
template<MEMFLAGS F>
class CHeapObj {
 public:
  ALWAYSINLINE void* operator new(size_t size) {
    return CHeapObjBase::operator new(size, F);
  }

  ALWAYSINLINE void* operator new(size_t size,
                                  const NativeCallStack& stack) {
    return CHeapObjBase::operator new(size, F, stack);
  }

  ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t& nt,
                                  const NativeCallStack& stack) throw() {
    return CHeapObjBase::operator new(size, F, nt, stack);
  }

  ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t& nt) throw() {
    return CHeapObjBase::operator new(size, F, nt);
  }

  ALWAYSINLINE void* operator new[](size_t size) {
    return CHeapObjBase::operator new[](size, F);
  }

  ALWAYSINLINE void* operator new[](size_t size,
                                    const NativeCallStack& stack) {
    return CHeapObjBase::operator new[](size, F, stack);
  }

  ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t& nt,
                                    const NativeCallStack& stack) throw() {
    return CHeapObjBase::operator new[](size, F, nt, stack);
  }

  ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t& nt) throw() {
    return CHeapObjBase::operator new[](size, F, nt);
  }

  void operator delete(void* p)     {
    CHeapObjBase::operator delete(p);
  }

  void operator delete [] (void* p) {
    CHeapObjBase::operator delete[](p);
  }
};

// Base class for objects allocated on the stack only.
// Calling new or delete will result in fatal error.

class StackObj {
 public:
  void* operator new(size_t size) = delete;
  void* operator new [](size_t size) = delete;
  void  operator delete(void* p) = delete;
  void  operator delete [](void* p) = delete;
};

// Base class for objects stored in Metaspace.
// Calling delete will result in fatal error.
//
// Do not inherit from something with a vptr because this class does
// not introduce one.  This class is used to allocate both shared read-only
// and shared read-write classes.
//

class ClassLoaderData;
class MetaspaceClosure;

class MetaspaceObj {
  // There are functions that all subtypes of MetaspaceObj are expected
  // to implement, so that templates which are defined for this class hierarchy
  // can work uniformly. Within the sub-hierarchy of Metadata, these are virtuals.
  // Elsewhere in the hierarchy of MetaspaceObj, type(), size(), and/or on_stack()
  // can be static if constant.
  //
  // The following functions are required by MetaspaceClosure:
  //   void metaspace_pointers_do(MetaspaceClosure* it) { <walk my refs> }
  //   int size() const { return align_up(sizeof(<This>), wordSize) / wordSize; }
  //   MetaspaceObj::Type type() const { return <This>Type; }
  //
  // The following functions are required by MetadataFactory::free_metadata():
  //   bool on_stack() { return false; }
  //   void deallocate_contents(ClassLoaderData* loader_data);

  friend class VMStructs;
  // When CDS is enabled, all shared metaspace objects are mapped
  // into a single contiguous memory block, so we can use these
  // two pointers to quickly determine if something is in the
  // shared metaspace.
  // When CDS is not enabled, both pointers are set to null.
  static void* _shared_metaspace_base;  // (inclusive) low address
  static void* _shared_metaspace_top;   // (exclusive) high address

 public:

  // Returns true if the pointer points to a valid MetaspaceObj. A valid
  // MetaspaceObj is MetaWord-aligned and contained within either
  // non-shared or shared metaspace.
  static bool is_valid(const MetaspaceObj* p);

#if INCLUDE_CDS
  static bool is_shared(const MetaspaceObj* p) {
    // If no shared metaspace regions are mapped, _shared_metaspace_{base,top} will
    // both be null and all values of p will be rejected quickly.
    return (((void*)p) < _shared_metaspace_top &&
            ((void*)p) >= _shared_metaspace_base);
  }
  bool is_shared() const { return MetaspaceObj::is_shared(this); }
#else
  static bool is_shared(const MetaspaceObj* p) { return false; }
  bool is_shared() const { return false; }
#endif

  void print_address_on(outputStream* st) const;  // nonvirtual address printing

  static void set_shared_metaspace_range(void* base, void* top) {
    _shared_metaspace_base = base;
    _shared_metaspace_top = top;
  }

  static void* shared_metaspace_base() { return _shared_metaspace_base; }
  static void* shared_metaspace_top()  { return _shared_metaspace_top;  }

#define METASPACE_OBJ_TYPES_DO(f) \
  f(Class) \
  f(Symbol) \
  f(TypeArrayU1) \
  f(TypeArrayU2) \
  f(TypeArrayU4) \
  f(TypeArrayU8) \
  f(TypeArrayOther) \
  f(Method) \
  f(ConstMethod) \
  f(MethodData) \
  f(ConstantPool) \
  f(ConstantPoolCache) \
  f(Annotations) \
  f(MethodCounters) \
  f(SharedClassPathEntry) \
  f(RecordComponent)

#define METASPACE_OBJ_TYPE_DECLARE(name) name ## Type,
#define METASPACE_OBJ_TYPE_NAME_CASE(name) case name ## Type: return #name;

  enum Type {
    // Types are MetaspaceObj::ClassType, MetaspaceObj::SymbolType, etc
    METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_DECLARE)
    _number_of_types
  };

  static const char * type_name(Type type) {
    switch(type) {
    METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_NAME_CASE)
    default:
      ShouldNotReachHere();
      return nullptr;
    }
  }

  static MetaspaceObj::Type array_type(size_t elem_size) {
    switch (elem_size) {
    case 1: return TypeArrayU1Type;
    case 2: return TypeArrayU2Type;
    case 4: return TypeArrayU4Type;
    case 8: return TypeArrayU8Type;
    default:
      return TypeArrayOtherType;
    }
  }

  void* operator new(size_t size, ClassLoaderData* loader_data,
                     size_t word_size,
                     Type type, JavaThread* thread) throw();
                     // can't use TRAPS from this header file.
  void* operator new(size_t size, ClassLoaderData* loader_data,
                     size_t word_size,
                     Type type) throw();
  void operator delete(void* p) { ShouldNotCallThis(); }

  // Declare a *static* method with the same signature in any subclass of MetaspaceObj
  // that should be read-only by default. See symbol.hpp for an example. This function
  // is used by the templates in metaspaceClosure.hpp
  static bool is_read_only_by_default() { return false; }
};

// Base class for classes that constitute name spaces.

class Arena;

extern char* resource_allocate_bytes(size_t size,
    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
extern char* resource_allocate_bytes(Thread* thread, size_t size,
    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
extern char* resource_reallocate_bytes( char *old, size_t old_size, size_t new_size,
    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
extern void resource_free_bytes( Thread* thread, char *old, size_t size );

//----------------------------------------------------------------------
// Base class for objects allocated in the resource area.
class ResourceObj {
 public:
  void* operator new(size_t size) {
    return resource_allocate_bytes(size);
  }

  void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
    return resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
  }

  void* operator new [](size_t size) throw() = delete;
  void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() = delete;

  void  operator delete(void* p) = delete;
  void  operator delete [](void* p) = delete;
};

class ArenaObj {
 public:
  void* operator new(size_t size, Arena *arena) throw();
  void* operator new [](size_t size, Arena *arena) throw() = delete;

  void* operator new [](size_t size) throw() = delete;
  void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() = delete;

  void  operator delete(void* p) = delete;
  void  operator delete [](void* p) = delete;
};

//----------------------------------------------------------------------
// Base class for objects allocated in the resource area per default.
// Optionally, objects may be allocated on the C heap with
// new (AnyObj::C_HEAP) Foo(...) or in an Arena with new (&arena).
// AnyObj's can be allocated within other objects, but don't use
// new or delete (allocation_type is unknown).  If new is used to allocate,
// use delete to deallocate.
class AnyObj {
 public:
  enum allocation_type { STACK_OR_EMBEDDED = 0, RESOURCE_AREA, C_HEAP, ARENA, allocation_mask = 0x3 };
  static void set_allocation_type(address res, allocation_type type) NOT_DEBUG_RETURN;
#ifdef ASSERT
 private:
  // When this object is allocated on stack the new() operator is not
  // called but garbage on stack may look like a valid allocation_type.
  // Store negated 'this' pointer when new() is called to distinguish cases.
  // Use second array's element for verification value to distinguish garbage.
  uintptr_t _allocation_t[2];
  bool is_type_set() const;
  void initialize_allocation_info();
 public:
  allocation_type get_allocation_type() const;
  bool allocated_on_stack_or_embedded() const { return get_allocation_type() == STACK_OR_EMBEDDED; }
  bool allocated_on_res_area() const { return get_allocation_type() == RESOURCE_AREA; }
  bool allocated_on_C_heap()   const { return get_allocation_type() == C_HEAP; }
  bool allocated_on_arena()    const { return get_allocation_type() == ARENA; }
protected:
  AnyObj(); // default constructor
  AnyObj(const AnyObj& r); // default copy constructor
  AnyObj& operator=(const AnyObj& r); // default copy assignment
  ~AnyObj();
#endif // ASSERT

 public:
  // CHeap allocations
  void* operator new(size_t size, MEMFLAGS flags) throw();
  void* operator new [](size_t size, MEMFLAGS flags) throw() = delete;
  void* operator new(size_t size, const std::nothrow_t&  nothrow_constant, MEMFLAGS flags) throw();
  void* operator new [](size_t size, const std::nothrow_t&  nothrow_constant, MEMFLAGS flags) throw() = delete;

  // Arena allocations
  void* operator new(size_t size, Arena *arena);
  void* operator new [](size_t size, Arena *arena) = delete;

  // Resource allocations
  void* operator new(size_t size) {
    address res = (address)resource_allocate_bytes(size);
    DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
    return res;
  }
  void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
    address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
    DEBUG_ONLY(if (res != nullptr) set_allocation_type(res, RESOURCE_AREA);)
    return res;
  }

  void* operator new [](size_t size) = delete;
  void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) = delete;
  void  operator delete(void* p);
  void  operator delete [](void* p) = delete;

#ifndef PRODUCT
  // Printing support
  void print() const;
  virtual void print_on(outputStream* st) const;
#endif // PRODUCT
};

// One of the following macros must be used when allocating an array
// or object to determine whether it should reside in the C heap on in
// the resource area.

#define NEW_RESOURCE_ARRAY(type, size)\
  (type*) resource_allocate_bytes((size) * sizeof(type))

#define NEW_RESOURCE_ARRAY_RETURN_NULL(type, size)\
  (type*) resource_allocate_bytes((size) * sizeof(type), AllocFailStrategy::RETURN_NULL)

#define NEW_RESOURCE_ARRAY_IN_THREAD(thread, type, size)\
  (type*) resource_allocate_bytes(thread, (size) * sizeof(type))

#define NEW_RESOURCE_ARRAY_IN_THREAD_RETURN_NULL(thread, type, size)\
  (type*) resource_allocate_bytes(thread, (size) * sizeof(type), AllocFailStrategy::RETURN_NULL)

#define REALLOC_RESOURCE_ARRAY(type, old, old_size, new_size)\
  (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type), (new_size) * sizeof(type))

#define REALLOC_RESOURCE_ARRAY_RETURN_NULL(type, old, old_size, new_size)\
  (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type),\
                                    (new_size) * sizeof(type), AllocFailStrategy::RETURN_NULL)

#define FREE_RESOURCE_ARRAY(type, old, size)\
  resource_free_bytes(Thread::current(), (char*)(old), (size) * sizeof(type))

#define FREE_RESOURCE_ARRAY_IN_THREAD(thread, type, old, size)\
  resource_free_bytes(thread, (char*)(old), (size) * sizeof(type))

#define FREE_FAST(old)\
    /* nop */

#define NEW_RESOURCE_OBJ(type)\
  NEW_RESOURCE_ARRAY(type, 1)

#define NEW_RESOURCE_OBJ_RETURN_NULL(type)\
  NEW_RESOURCE_ARRAY_RETURN_NULL(type, 1)

#define NEW_C_HEAP_ARRAY3(type, size, memflags, pc, allocfail)\
  (type*) AllocateHeap((size) * sizeof(type), memflags, pc, allocfail)

#define NEW_C_HEAP_ARRAY2(type, size, memflags, pc)\
  (type*) (AllocateHeap((size) * sizeof(type), memflags, pc))

#define NEW_C_HEAP_ARRAY(type, size, memflags)\
  (type*) (AllocateHeap((size) * sizeof(type), memflags))

#define NEW_C_HEAP_ARRAY2_RETURN_NULL(type, size, memflags, pc)\
  NEW_C_HEAP_ARRAY3(type, (size), memflags, pc, AllocFailStrategy::RETURN_NULL)

#define NEW_C_HEAP_ARRAY_RETURN_NULL(type, size, memflags)\
  NEW_C_HEAP_ARRAY2(type, (size), memflags, AllocFailStrategy::RETURN_NULL)

#define REALLOC_C_HEAP_ARRAY(type, old, size, memflags)\
  (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags))

#define REALLOC_C_HEAP_ARRAY_RETURN_NULL(type, old, size, memflags)\
  (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags, AllocFailStrategy::RETURN_NULL))

#define FREE_C_HEAP_ARRAY(type, old) \
  FreeHeap((char*)(old))

// allocate type in heap without calling ctor
#define NEW_C_HEAP_OBJ(type, memflags)\
  NEW_C_HEAP_ARRAY(type, 1, memflags)

#define NEW_C_HEAP_OBJ_RETURN_NULL(type, memflags)\
  NEW_C_HEAP_ARRAY_RETURN_NULL(type, 1, memflags)

// deallocate obj of type in heap without calling dtor
#define FREE_C_HEAP_OBJ(objname)\
  FreeHeap((char*)objname);


//------------------------------ReallocMark---------------------------------
// Code which uses REALLOC_RESOURCE_ARRAY should check an associated
// ReallocMark, which is declared in the same scope as the reallocated
// pointer.  Any operation that could __potentially__ cause a reallocation
// should check the ReallocMark.
class ReallocMark: public StackObj {
protected:
  NOT_PRODUCT(int _nesting;)

public:
  ReallocMark()   PRODUCT_RETURN;
  void check()    PRODUCT_RETURN;
};

// Helper class to allocate arrays that may become large.
// Uses the OS malloc for allocations smaller than ArrayAllocatorMallocLimit
// and uses mapped memory for larger allocations.
// Most OS mallocs do something similar but Solaris malloc does not revert
// to mapped memory for large allocations. By default ArrayAllocatorMallocLimit
// is set so that we always use malloc except for Solaris where we set the
// limit to get mapped memory.
template <class E>
class ArrayAllocator : public AllStatic {
 private:
  static bool should_use_malloc(size_t length);

  static E* allocate_malloc(size_t length, MEMFLAGS flags);
  static E* allocate_mmap(size_t length, MEMFLAGS flags);

  static E* reallocate_malloc(E* addr, size_t new_length, MEMFLAGS flags);

  static void free_malloc(E* addr, size_t length);
  static void free_mmap(E* addr, size_t length);

 public:
  static E* allocate(size_t length, MEMFLAGS flags);
  static E* reallocate(E* old_addr, size_t old_length, size_t new_length, MEMFLAGS flags);
  static void free(E* addr, size_t length);
};

// Uses mmapped memory for all allocations. All allocations are initially
// zero-filled. No pre-touching.
template <class E>
class MmapArrayAllocator : public AllStatic {
 private:
  static size_t size_for(size_t length);

 public:
  static E* allocate_or_null(size_t length, MEMFLAGS flags);
  static E* allocate(size_t length, MEMFLAGS flags);
  static void free(E* addr, size_t length);
};

// Uses malloc:ed memory for all allocations.
template <class E>
class MallocArrayAllocator : public AllStatic {
 public:
  static size_t size_for(size_t length);

  static E* allocate(size_t length, MEMFLAGS flags);
  static E* reallocate(E* addr, size_t new_length, MEMFLAGS flags);
  static void free(E* addr);
};

#endif // SHARE_MEMORY_ALLOCATION_HPP