1 /*
  2  * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #ifndef SHARE_MEMORY_ALLOCATION_HPP
 26 #define SHARE_MEMORY_ALLOCATION_HPP
 27 
 28 #include "memory/allStatic.hpp"
 29 #include "nmt/memflags.hpp"
 30 #include "utilities/debug.hpp"
 31 #include "utilities/globalDefinitions.hpp"
 32 #include "utilities/macros.hpp"
 33 
 34 #include <new>
 35 
 36 class outputStream;
 37 class Thread;
 38 class JavaThread;
 39 
 40 class AllocFailStrategy {
 41 public:
 42   enum AllocFailEnum { EXIT_OOM, RETURN_NULL };
 43 };
 44 typedef AllocFailStrategy::AllocFailEnum AllocFailType;
 45 
 46 // The virtual machine must never call one of the implicitly declared
 47 // global allocation or deletion functions.  (Such calls may result in
 48 // link-time or run-time errors.)  For convenience and documentation of
 49 // intended use, classes in the virtual machine may be derived from one
 50 // of the following allocation classes, some of which define allocation
 51 // and deletion functions.
 52 // Note: std::malloc and std::free should never called directly.
 53 
 54 //
 55 // For objects allocated in the resource area (see resourceArea.hpp).
 56 // - ResourceObj
 57 //
 58 // For objects allocated in the C-heap (managed by: free & malloc and tracked with NMT)
 59 // - CHeapObj
 60 //
 61 // For objects allocated on the stack.
 62 // - StackObj
 63 //
 64 // For classes used as name spaces.
 65 // - AllStatic
 66 //
 67 // For classes in Metaspace (class data)
 68 // - MetaspaceObj
 69 //
 70 // The printable subclasses are used for debugging and define virtual
 71 // member functions for printing. Classes that avoid allocating the
 72 // vtbl entries in the objects should therefore not be the printable
 73 // subclasses.
 74 //
 75 // The following macros and function should be used to allocate memory
 76 // directly in the resource area or in the C-heap, The _OBJ variants
 77 // of the NEW/FREE_C_HEAP macros are used for alloc/dealloc simple
 78 // objects which are not inherited from CHeapObj, note constructor and
 79 // destructor are not called. The preferable way to allocate objects
 80 // is using the new operator.
 81 //
 82 // WARNING: The array variant must only be used for a homogeneous array
 83 // where all objects are of the exact type specified. If subtypes are
 84 // stored in the array then must pay attention to calling destructors
 85 // at needed.
 86 //
 87 // NEW_RESOURCE_ARRAY*
 88 // REALLOC_RESOURCE_ARRAY*
 89 // FREE_RESOURCE_ARRAY*
 90 // NEW_RESOURCE_OBJ*
 91 // NEW_C_HEAP_ARRAY*
 92 // REALLOC_C_HEAP_ARRAY*
 93 // FREE_C_HEAP_ARRAY*
 94 // NEW_C_HEAP_OBJ*
 95 // FREE_C_HEAP_OBJ
 96 //
 97 // char* AllocateHeap(size_t size, MEMFLAGS flags, const NativeCallStack& stack, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 98 // char* AllocateHeap(size_t size, MEMFLAGS flags, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 99 // char* ReallocateHeap(char *old, size_t size, MEMFLAGS flag, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
100 // void FreeHeap(void* p);
101 //
102 
103 extern bool NMT_track_callsite;
104 
105 class NativeCallStack;
106 
107 
108 char* AllocateHeap(size_t size,
109                    MEMFLAGS flags,
110                    const NativeCallStack& stack,
111                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
112 char* AllocateHeap(size_t size,
113                    MEMFLAGS flags,
114                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
115 
116 char* ReallocateHeap(char *old,
117                      size_t size,
118                      MEMFLAGS flag,
119                      AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
120 
121 // handles null pointers
122 void FreeHeap(void* p);
123 
124 class CHeapObjBase {
125  public:
126   ALWAYSINLINE void* operator new(size_t size, MEMFLAGS f) {
127     return AllocateHeap(size, f);
128   }
129 
130   ALWAYSINLINE void* operator new(size_t size,
131                                   MEMFLAGS f,
132                                   const NativeCallStack& stack) {
133     return AllocateHeap(size, f, stack);
134   }
135 
136   ALWAYSINLINE void* operator new(size_t size,
137                                   MEMFLAGS f,
138                                   const std::nothrow_t&,
139                                   const NativeCallStack& stack) throw() {
140     return AllocateHeap(size, f, stack, AllocFailStrategy::RETURN_NULL);
141   }
142 
143   ALWAYSINLINE void* operator new(size_t size,
144                                   MEMFLAGS f,
145                                   const std::nothrow_t&) throw() {
146     return AllocateHeap(size, f, AllocFailStrategy::RETURN_NULL);
147   }
148 
149   ALWAYSINLINE void* operator new[](size_t size, MEMFLAGS f) {
150     return AllocateHeap(size, f);
151   }
152 
153   ALWAYSINLINE void* operator new[](size_t size,
154                                     MEMFLAGS f,
155                                     const NativeCallStack& stack) {
156     return AllocateHeap(size, f, stack);
157   }
158 
159   ALWAYSINLINE void* operator new[](size_t size,
160                                     MEMFLAGS f,
161                                     const std::nothrow_t&,
162                                     const NativeCallStack& stack) throw() {
163     return AllocateHeap(size, f, stack, AllocFailStrategy::RETURN_NULL);
164   }
165 
166   ALWAYSINLINE void* operator new[](size_t size,
167                                     MEMFLAGS f,
168                                     const std::nothrow_t&) throw() {
169     return AllocateHeap(size, f, AllocFailStrategy::RETURN_NULL);
170   }
171 
172   void operator delete(void* p)     { FreeHeap(p); }
173   void operator delete [] (void* p) { FreeHeap(p); }
174 };
175 
176 // Uses the implicitly static new and delete operators of CHeapObjBase
177 template<MEMFLAGS F>
178 class CHeapObj {
179  public:
180   ALWAYSINLINE void* operator new(size_t size) {
181     return CHeapObjBase::operator new(size, F);
182   }
183 
184   ALWAYSINLINE void* operator new(size_t size,
185                                   const NativeCallStack& stack) {
186     return CHeapObjBase::operator new(size, F, stack);
187   }
188 
189   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t& nt,
190                                   const NativeCallStack& stack) throw() {
191     return CHeapObjBase::operator new(size, F, nt, stack);
192   }
193 
194   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t& nt) throw() {
195     return CHeapObjBase::operator new(size, F, nt);
196   }
197 
198   ALWAYSINLINE void* operator new[](size_t size) {
199     return CHeapObjBase::operator new[](size, F);
200   }
201 
202   ALWAYSINLINE void* operator new[](size_t size,
203                                     const NativeCallStack& stack) {
204     return CHeapObjBase::operator new[](size, F, stack);
205   }
206 
207   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t& nt,
208                                     const NativeCallStack& stack) throw() {
209     return CHeapObjBase::operator new[](size, F, nt, stack);
210   }
211 
212   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t& nt) throw() {
213     return CHeapObjBase::operator new[](size, F, nt);
214   }
215 
216   void operator delete(void* p)     {
217     CHeapObjBase::operator delete(p);
218   }
219 
220   void operator delete [] (void* p) {
221     CHeapObjBase::operator delete[](p);
222   }
223 };
224 
225 // Base class for objects allocated on the stack only.
226 // Calling new or delete will result in fatal error.
227 
228 class StackObj {
229  public:
230   void* operator new(size_t size) = delete;
231   void* operator new [](size_t size) = delete;
232   void  operator delete(void* p) = delete;
233   void  operator delete [](void* p) = delete;
234 };
235 
236 // Base class for objects stored in Metaspace.
237 // Calling delete will result in fatal error.
238 //
239 // Do not inherit from something with a vptr because this class does
240 // not introduce one.  This class is used to allocate both shared read-only
241 // and shared read-write classes.
242 //
243 
244 class ClassLoaderData;
245 class MetaspaceClosure;
246 
247 class MetaspaceObj {
248   // There are functions that all subtypes of MetaspaceObj are expected
249   // to implement, so that templates which are defined for this class hierarchy
250   // can work uniformly. Within the sub-hierarchy of Metadata, these are virtuals.
251   // Elsewhere in the hierarchy of MetaspaceObj, type(), size(), and/or on_stack()
252   // can be static if constant.
253   //
254   // The following functions are required by MetaspaceClosure:
255   //   void metaspace_pointers_do(MetaspaceClosure* it) { <walk my refs> }
256   //   int size() const { return align_up(sizeof(<This>), wordSize) / wordSize; }
257   //   MetaspaceObj::Type type() const { return <This>Type; }
258   //
259   // The following functions are required by MetadataFactory::free_metadata():
260   //   bool on_stack() { return false; }
261   //   void deallocate_contents(ClassLoaderData* loader_data);
262 
263   friend class VMStructs;
264   // When CDS is enabled, all shared metaspace objects are mapped
265   // into a single contiguous memory block, so we can use these
266   // two pointers to quickly determine if something is in the
267   // shared metaspace.
268   // When CDS is not enabled, both pointers are set to null.
269   static void* _shared_metaspace_base;  // (inclusive) low address
270   static void* _shared_metaspace_top;   // (exclusive) high address
271 
272  public:
273 
274   // Returns true if the pointer points to a valid MetaspaceObj. A valid
275   // MetaspaceObj is MetaWord-aligned and contained within either
276   // non-shared or shared metaspace.
277   static bool is_valid(const MetaspaceObj* p);
278 
279 #if INCLUDE_CDS
280   static bool is_shared(const MetaspaceObj* p) {
281     // If no shared metaspace regions are mapped, _shared_metaspace_{base,top} will
282     // both be null and all values of p will be rejected quickly.
283     return (((void*)p) < _shared_metaspace_top &&
284             ((void*)p) >= _shared_metaspace_base);
285   }
286   bool is_shared() const { return MetaspaceObj::is_shared(this); }
287 #else
288   static bool is_shared(const MetaspaceObj* p) { return false; }
289   bool is_shared() const { return false; }
290 #endif
291 
292   void print_address_on(outputStream* st) const;  // nonvirtual address printing
293 
294   static void set_shared_metaspace_range(void* base, void* top) {
295     _shared_metaspace_base = base;
296     _shared_metaspace_top = top;
297   }
298 
299   static void* shared_metaspace_base() { return _shared_metaspace_base; }
300   static void* shared_metaspace_top()  { return _shared_metaspace_top;  }
301 
302 #define METASPACE_OBJ_TYPES_DO(f) \
303   f(Class) \
304   f(Symbol) \
305   f(TypeArrayU1) \
306   f(TypeArrayU2) \
307   f(TypeArrayU4) \
308   f(TypeArrayU8) \
309   f(TypeArrayOther) \
310   f(Method) \
311   f(ConstMethod) \
312   f(MethodData) \
313   f(ConstantPool) \
314   f(ConstantPoolCache) \
315   f(Annotations) \
316   f(MethodCounters) \
317   f(RecordComponent) \
318   f(KlassTrainingData) \
319   f(MethodTrainingData) \
320   f(CompileTrainingData) \
321   f(SharedClassPathEntry)
322 
323 #define METASPACE_OBJ_TYPE_DECLARE(name) name ## Type,
324 #define METASPACE_OBJ_TYPE_NAME_CASE(name) case name ## Type: return #name;
325 
326   enum Type {
327     // Types are MetaspaceObj::ClassType, MetaspaceObj::SymbolType, etc
328     METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_DECLARE)
329     _number_of_types
330   };
331 
332   static const char * type_name(Type type) {
333     switch(type) {
334     METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_NAME_CASE)
335     default:
336       ShouldNotReachHere();
337       return nullptr;
338     }
339   }
340 
341   static bool is_training_data(Type type) {
342     return (type == Type::KlassTrainingDataType)  ||
343            (type == Type::MethodTrainingDataType) ||
344            (type == Type::CompileTrainingDataType);
345   }
346 
347   static MetaspaceObj::Type array_type(size_t elem_size) {
348     switch (elem_size) {
349     case 1: return TypeArrayU1Type;
350     case 2: return TypeArrayU2Type;
351     case 4: return TypeArrayU4Type;
352     case 8: return TypeArrayU8Type;
353     default:
354       return TypeArrayOtherType;
355     }
356   }
357 
358   void* operator new(size_t size, ClassLoaderData* loader_data,
359                      size_t word_size,
360                      Type type, JavaThread* thread) throw();
361                      // can't use TRAPS from this header file.
362   void* operator new(size_t size, ClassLoaderData* loader_data,
363                      size_t word_size,
364                      Type type) throw();
365 
366   // HACK -- this is used for allocating training data. See JDK-8331086
367   void* operator new(size_t size, MEMFLAGS flags) throw();
368   void operator delete(void* p) { ShouldNotCallThis(); }
369 
370   // Declare a *static* method with the same signature in any subclass of MetaspaceObj
371   // that should be read-only by default. See symbol.hpp for an example. This function
372   // is used by the templates in metaspaceClosure.hpp
373   static bool is_read_only_by_default() { return false; }
374 };
375 
376 // Base class for classes that constitute name spaces.
377 
378 class Arena;
379 
380 extern char* resource_allocate_bytes(size_t size,
381     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
382 extern char* resource_allocate_bytes(Thread* thread, size_t size,
383     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
384 extern char* resource_reallocate_bytes( char *old, size_t old_size, size_t new_size,
385     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
386 extern void resource_free_bytes( Thread* thread, char *old, size_t size );
387 
388 //----------------------------------------------------------------------
389 // Base class for objects allocated in the resource area.
390 class ResourceObj {
391  public:
392   void* operator new(size_t size) {
393     return resource_allocate_bytes(size);
394   }
395 
396   void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
397     return resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
398   }
399 
400   void* operator new [](size_t size) throw() = delete;
401   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() = delete;
402 
403   void  operator delete(void* p) = delete;
404   void  operator delete [](void* p) = delete;
405 };
406 
407 class ArenaObj {
408  public:
409   void* operator new(size_t size, Arena *arena) throw();
410   void* operator new [](size_t size, Arena *arena) throw() = delete;
411 
412   void* operator new [](size_t size) throw() = delete;
413   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() = delete;
414 
415   void  operator delete(void* p) = delete;
416   void  operator delete [](void* p) = delete;
417 };
418 
419 //----------------------------------------------------------------------
420 // Base class for objects allocated in the resource area per default.
421 // Optionally, objects may be allocated on the C heap with
422 // new (AnyObj::C_HEAP) Foo(...) or in an Arena with new (&arena).
423 // AnyObj's can be allocated within other objects, but don't use
424 // new or delete (allocation_type is unknown).  If new is used to allocate,
425 // use delete to deallocate.
426 class AnyObj {
427  public:
428   enum allocation_type { STACK_OR_EMBEDDED = 0, RESOURCE_AREA, C_HEAP, ARENA, allocation_mask = 0x3 };
429   static void set_allocation_type(address res, allocation_type type) NOT_DEBUG_RETURN;
430 #ifdef ASSERT
431  private:
432   // When this object is allocated on stack the new() operator is not
433   // called but garbage on stack may look like a valid allocation_type.
434   // Store negated 'this' pointer when new() is called to distinguish cases.
435   // Use second array's element for verification value to distinguish garbage.
436   uintptr_t _allocation_t[2];
437   bool is_type_set() const;
438   void initialize_allocation_info();
439  public:
440   allocation_type get_allocation_type() const;
441   bool allocated_on_stack_or_embedded() const { return get_allocation_type() == STACK_OR_EMBEDDED; }
442   bool allocated_on_res_area() const { return get_allocation_type() == RESOURCE_AREA; }
443   bool allocated_on_C_heap()   const { return get_allocation_type() == C_HEAP; }
444   bool allocated_on_arena()    const { return get_allocation_type() == ARENA; }
445 protected:
446   AnyObj(); // default constructor
447   AnyObj(const AnyObj& r); // default copy constructor
448   AnyObj& operator=(const AnyObj& r); // default copy assignment
449   ~AnyObj();
450 #endif // ASSERT
451 
452  public:
453   // CHeap allocations
454   void* operator new(size_t size, MEMFLAGS flags) throw();
455   void* operator new [](size_t size, MEMFLAGS flags) throw() = delete;
456   void* operator new(size_t size, const std::nothrow_t&  nothrow_constant, MEMFLAGS flags) throw();
457   void* operator new [](size_t size, const std::nothrow_t&  nothrow_constant, MEMFLAGS flags) throw() = delete;
458 
459   // Arena allocations
460   void* operator new(size_t size, Arena *arena);
461   void* operator new [](size_t size, Arena *arena) = delete;
462 
463   // Resource allocations
464   void* operator new(size_t size) {
465     address res = (address)resource_allocate_bytes(size);
466     DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
467     return res;
468   }
469   void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
470     address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
471     DEBUG_ONLY(if (res != nullptr) set_allocation_type(res, RESOURCE_AREA);)
472     return res;
473   }
474 
475   void* operator new [](size_t size) = delete;
476   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) = delete;
477   void  operator delete(void* p);
478   void  operator delete [](void* p) = delete;
479 
480 #ifndef PRODUCT
481   // Printing support
482   void print() const;
483   virtual void print_on(outputStream* st) const;
484 #endif // PRODUCT
485 };
486 
487 // One of the following macros must be used when allocating an array
488 // or object to determine whether it should reside in the C heap on in
489 // the resource area.
490 
491 #define NEW_RESOURCE_ARRAY(type, size)\
492   (type*) resource_allocate_bytes((size) * sizeof(type))
493 
494 #define NEW_RESOURCE_ARRAY_RETURN_NULL(type, size)\
495   (type*) resource_allocate_bytes((size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
496 
497 #define NEW_RESOURCE_ARRAY_IN_THREAD(thread, type, size)\
498   (type*) resource_allocate_bytes(thread, (size) * sizeof(type))
499 
500 #define NEW_RESOURCE_ARRAY_IN_THREAD_RETURN_NULL(thread, type, size)\
501   (type*) resource_allocate_bytes(thread, (size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
502 
503 #define REALLOC_RESOURCE_ARRAY(type, old, old_size, new_size)\
504   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type), (new_size) * sizeof(type))
505 
506 #define REALLOC_RESOURCE_ARRAY_RETURN_NULL(type, old, old_size, new_size)\
507   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type),\
508                                     (new_size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
509 
510 #define FREE_RESOURCE_ARRAY(type, old, size)\
511   resource_free_bytes(Thread::current(), (char*)(old), (size) * sizeof(type))
512 
513 #define FREE_RESOURCE_ARRAY_IN_THREAD(thread, type, old, size)\
514   resource_free_bytes(thread, (char*)(old), (size) * sizeof(type))
515 
516 #define FREE_FAST(old)\
517     /* nop */
518 
519 #define NEW_RESOURCE_OBJ(type)\
520   NEW_RESOURCE_ARRAY(type, 1)
521 
522 #define NEW_RESOURCE_OBJ_RETURN_NULL(type)\
523   NEW_RESOURCE_ARRAY_RETURN_NULL(type, 1)
524 
525 #define NEW_C_HEAP_ARRAY3(type, size, memflags, pc, allocfail)\
526   (type*) AllocateHeap((size) * sizeof(type), memflags, pc, allocfail)
527 
528 #define NEW_C_HEAP_ARRAY2(type, size, memflags, pc)\
529   (type*) (AllocateHeap((size) * sizeof(type), memflags, pc))
530 
531 #define NEW_C_HEAP_ARRAY(type, size, memflags)\
532   (type*) (AllocateHeap((size) * sizeof(type), memflags))
533 
534 #define NEW_C_HEAP_ARRAY2_RETURN_NULL(type, size, memflags, pc)\
535   NEW_C_HEAP_ARRAY3(type, (size), memflags, pc, AllocFailStrategy::RETURN_NULL)
536 
537 #define NEW_C_HEAP_ARRAY_RETURN_NULL(type, size, memflags)\
538   NEW_C_HEAP_ARRAY2(type, (size), memflags, AllocFailStrategy::RETURN_NULL)
539 
540 #define REALLOC_C_HEAP_ARRAY(type, old, size, memflags)\
541   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags))
542 
543 #define REALLOC_C_HEAP_ARRAY_RETURN_NULL(type, old, size, memflags)\
544   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), memflags, AllocFailStrategy::RETURN_NULL))
545 
546 #define FREE_C_HEAP_ARRAY(type, old) \
547   FreeHeap((char*)(old))
548 
549 // allocate type in heap without calling ctor
550 #define NEW_C_HEAP_OBJ(type, memflags)\
551   NEW_C_HEAP_ARRAY(type, 1, memflags)
552 
553 #define NEW_C_HEAP_OBJ_RETURN_NULL(type, memflags)\
554   NEW_C_HEAP_ARRAY_RETURN_NULL(type, 1, memflags)
555 
556 // deallocate obj of type in heap without calling dtor
557 #define FREE_C_HEAP_OBJ(objname)\
558   FreeHeap((char*)objname);
559 
560 
561 //------------------------------ReallocMark---------------------------------
562 // Code which uses REALLOC_RESOURCE_ARRAY should check an associated
563 // ReallocMark, which is declared in the same scope as the reallocated
564 // pointer.  Any operation that could __potentially__ cause a reallocation
565 // should check the ReallocMark.
566 class ReallocMark: public StackObj {
567 protected:
568   NOT_PRODUCT(int _nesting;)
569 
570 public:
571   ReallocMark()   PRODUCT_RETURN;
572   void check()    PRODUCT_RETURN;
573 };
574 
575 // Uses mmapped memory for all allocations. All allocations are initially
576 // zero-filled. No pre-touching.
577 template <class E>
578 class MmapArrayAllocator : public AllStatic {
579  private:
580   static size_t size_for(size_t length);
581 
582  public:
583   static E* allocate_or_null(size_t length, MEMFLAGS flags);
584   static E* allocate(size_t length, MEMFLAGS flags);
585   static void free(E* addr, size_t length);
586 };
587 
588 // Uses malloc:ed memory for all allocations.
589 template <class E>
590 class MallocArrayAllocator : public AllStatic {
591  public:
592   static size_t size_for(size_t length);
593 
594   static E* allocate(size_t length, MEMFLAGS flags);
595   static E* reallocate(E* addr, size_t new_length, MEMFLAGS flags);
596   static void free(E* addr);
597 };
598 
599 #endif // SHARE_MEMORY_ALLOCATION_HPP