1 /*
  2  * Copyright (c) 1997, 2025, 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.
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  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  *
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 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.
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 24 
 25 #ifndef SHARE_MEMORY_ALLOCATION_HPP
 26 #define SHARE_MEMORY_ALLOCATION_HPP
 27 
 28 #include "cppstdlib/new.hpp"
 29 #include "memory/allStatic.hpp"
 30 #include "nmt/memTag.hpp"
 31 #include "utilities/debug.hpp"
 32 #include "utilities/globalDefinitions.hpp"
 33 #include "utilities/macros.hpp"
 34 
 35 class outputStream;
 36 class Thread;
 37 class JavaThread;
 38 
 39 class AllocFailStrategy {
 40 public:
 41   enum AllocFailEnum { EXIT_OOM, RETURN_NULL };
 42 };
 43 typedef AllocFailStrategy::AllocFailEnum AllocFailType;
 44 
 45 // The virtual machine must never call one of the implicitly declared
 46 // global allocation or deletion functions.  (Such calls may result in
 47 // link-time or run-time errors.)  For convenience and documentation of
 48 // intended use, classes in the virtual machine may be derived from one
 49 // of the following allocation classes, some of which define allocation
 50 // and deletion functions.
 51 // Note: std::malloc and std::free should never called directly.
 52 
 53 //
 54 // For objects allocated in the resource area (see resourceArea.hpp).
 55 // - ResourceObj
 56 //
 57 // For objects allocated in the C-heap (managed by: free & malloc and tracked with NMT)
 58 // - CHeapObj
 59 //
 60 // For objects allocated on the stack.
 61 // - StackObj
 62 //
 63 // For classes used as name spaces.
 64 // - AllStatic
 65 //
 66 // For classes in Metaspace (class data)
 67 // - MetaspaceObj
 68 //
 69 // The printable subclasses are used for debugging and define virtual
 70 // member functions for printing. Classes that avoid allocating the
 71 // vtbl entries in the objects should therefore not be the printable
 72 // subclasses.
 73 //
 74 // The following macros and function should be used to allocate memory
 75 // directly in the resource area or in the C-heap, The _OBJ variants
 76 // of the NEW/FREE_C_HEAP macros are used for alloc/dealloc simple
 77 // objects which are not inherited from CHeapObj, note constructor and
 78 // destructor are not called. The preferable way to allocate objects
 79 // is using the new operator.
 80 //
 81 // WARNING: The array variant must only be used for a homogeneous array
 82 // where all objects are of the exact type specified. If subtypes are
 83 // stored in the array then must pay attention to calling destructors
 84 // at needed.
 85 //
 86 // NEW_RESOURCE_ARRAY*
 87 // REALLOC_RESOURCE_ARRAY*
 88 // FREE_RESOURCE_ARRAY*
 89 // NEW_RESOURCE_OBJ*
 90 // NEW_C_HEAP_ARRAY*
 91 // REALLOC_C_HEAP_ARRAY*
 92 // FREE_C_HEAP_ARRAY*
 93 // NEW_C_HEAP_OBJ*
 94 // FREE_C_HEAP_OBJ
 95 //
 96 // char* AllocateHeap(size_t size, MemTag mem_tag, const NativeCallStack& stack, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 97 // char* AllocateHeap(size_t size, MemTag mem_tag, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 98 // char* ReallocateHeap(char *old, size_t size, MemTag mem_tag, AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
 99 // void FreeHeap(void* p);
100 //
101 
102 extern bool NMT_track_callsite;
103 
104 class NativeCallStack;
105 
106 
107 char* AllocateHeap(size_t size,
108                    MemTag mem_tag,
109                    const NativeCallStack& stack,
110                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
111 char* AllocateHeap(size_t size,
112                    MemTag mem_tag,
113                    AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
114 
115 char* ReallocateHeap(char *old,
116                      size_t size,
117                      MemTag mem_tag,
118                      AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
119 
120 // handles null pointers
121 void FreeHeap(void* p);
122 
123 class CHeapObjBase {
124  public:
125   ALWAYSINLINE void* operator new(size_t size, MemTag mem_tag) {
126     return AllocateHeap(size, mem_tag);
127   }
128 
129   ALWAYSINLINE void* operator new(size_t size,
130                                   MemTag mem_tag,
131                                   const NativeCallStack& stack) {
132     return AllocateHeap(size, mem_tag, stack);
133   }
134 
135   ALWAYSINLINE void* operator new(size_t size,
136                                   MemTag mem_tag,
137                                   const std::nothrow_t&,
138                                   const NativeCallStack& stack) throw() {
139     return AllocateHeap(size, mem_tag, stack, AllocFailStrategy::RETURN_NULL);
140   }
141 
142   ALWAYSINLINE void* operator new(size_t size,
143                                   MemTag mem_tag,
144                                   const std::nothrow_t&) throw() {
145     return AllocateHeap(size, mem_tag, AllocFailStrategy::RETURN_NULL);
146   }
147 
148   ALWAYSINLINE void* operator new[](size_t size, MemTag mem_tag) {
149     return AllocateHeap(size, mem_tag);
150   }
151 
152   ALWAYSINLINE void* operator new[](size_t size,
153                                     MemTag mem_tag,
154                                     const NativeCallStack& stack) {
155     return AllocateHeap(size, mem_tag, stack);
156   }
157 
158   ALWAYSINLINE void* operator new[](size_t size,
159                                     MemTag mem_tag,
160                                     const std::nothrow_t&,
161                                     const NativeCallStack& stack) throw() {
162     return AllocateHeap(size, mem_tag, stack, AllocFailStrategy::RETURN_NULL);
163   }
164 
165   ALWAYSINLINE void* operator new[](size_t size,
166                                     MemTag mem_tag,
167                                     const std::nothrow_t&) throw() {
168     return AllocateHeap(size, mem_tag, AllocFailStrategy::RETURN_NULL);
169   }
170 
171   void operator delete(void* p)     { FreeHeap(p); }
172   void operator delete [] (void* p) { FreeHeap(p); }
173 };
174 
175 // Uses the implicitly static new and delete operators of CHeapObjBase
176 template<MemTag MT>
177 class CHeapObj {
178  public:
179   ALWAYSINLINE void* operator new(size_t size) {
180     return CHeapObjBase::operator new(size, MT);
181   }
182 
183   ALWAYSINLINE void* operator new(size_t size,
184                                   const NativeCallStack& stack) {
185     return CHeapObjBase::operator new(size, MT, stack);
186   }
187 
188   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t& nt,
189                                   const NativeCallStack& stack) throw() {
190     return CHeapObjBase::operator new(size, MT, nt, stack);
191   }
192 
193   ALWAYSINLINE void* operator new(size_t size, const std::nothrow_t& nt) throw() {
194     return CHeapObjBase::operator new(size, MT, nt);
195   }
196 
197   ALWAYSINLINE void* operator new[](size_t size) {
198     return CHeapObjBase::operator new[](size, MT);
199   }
200 
201   ALWAYSINLINE void* operator new[](size_t size,
202                                     const NativeCallStack& stack) {
203     return CHeapObjBase::operator new[](size, MT, stack);
204   }
205 
206   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t& nt,
207                                     const NativeCallStack& stack) throw() {
208     return CHeapObjBase::operator new[](size, MT, nt, stack);
209   }
210 
211   ALWAYSINLINE void* operator new[](size_t size, const std::nothrow_t& nt) throw() {
212     return CHeapObjBase::operator new[](size, MT, nt);
213   }
214 
215   void operator delete(void* p)     {
216     CHeapObjBase::operator delete(p);
217   }
218 
219   void operator delete [] (void* p) {
220     CHeapObjBase::operator delete[](p);
221   }
222 };
223 
224 // Base class for objects allocated on the stack only.
225 // Calling new or delete will result in fatal error.
226 
227 class StackObj {
228  public:
229   void* operator new(size_t size) = delete;
230   void* operator new [](size_t size) = delete;
231   void  operator delete(void* p) = delete;
232   void  operator delete [](void* p) = delete;
233 };
234 
235 // Base class for objects stored in Metaspace.
236 // Calling delete will result in fatal error.
237 //
238 // Do not inherit from something with a vptr because this class does
239 // not introduce one.  This class is used to allocate both shared read-only
240 // and shared read-write classes.
241 //
242 
243 class ClassLoaderData;
244 class MetaspaceClosure;
245 
246 class MetaspaceObj {
247   // There are functions that all subtypes of MetaspaceObj are expected
248   // to implement, so that templates which are defined for this class hierarchy
249   // can work uniformly. Within the sub-hierarchy of Metadata, these are virtuals.
250   // Elsewhere in the hierarchy of MetaspaceObj, type(), size(), and/or on_stack()
251   // can be static if constant.
252   //
253   // The following functions are required by MetaspaceClosure:
254   //   void metaspace_pointers_do(MetaspaceClosure* it) { <walk my refs> }
255   //   int size() const { return align_up(sizeof(<This>), wordSize) / wordSize; }
256   //   MetaspaceObj::Type type() const { return <This>Type; }
257   //
258   // The following functions are required by MetadataFactory::free_metadata():
259   //   bool on_stack() { return false; }
260   //   void deallocate_contents(ClassLoaderData* loader_data);
261 
262   friend class VMStructs;
263   // All metsapce objects in the AOT cache (CDS archive) are mapped
264   // into a single contiguous memory block, so we can use these
265   // two pointers to quickly determine if a MetaspaceObj is in the
266   // AOT cache.
267   // When AOT/CDS is not enabled, both pointers are set to null.
268   static void* _aot_metaspace_base;  // (inclusive) low address
269   static void* _aot_metaspace_top;   // (exclusive) high address
270 
271  public:
272 
273   // Returns true if the pointer points to a valid MetaspaceObj. A valid
274   // MetaspaceObj is MetaWord-aligned and contained within either
275   // regular- or aot metaspace.
276   static bool is_valid(const MetaspaceObj* p);
277 
278 #if INCLUDE_CDS
279   static bool in_aot_cache(const MetaspaceObj* p) {
280     // If no shared metaspace regions are mapped, _aot_metaspace_{base,top} will
281     // both be null and all values of p will be rejected quickly.
282     return (((void*)p) < _aot_metaspace_top &&
283             ((void*)p) >= _aot_metaspace_base);
284   }
285   bool in_aot_cache() const { return MetaspaceObj::in_aot_cache(this); }
286 #else
287   static bool in_aot_cache(const MetaspaceObj* p) { return false; }
288   bool in_aot_cache() const { return false; }
289 #endif
290 
291   void print_address_on(outputStream* st) const;  // nonvirtual address printing
292 
293   static void set_aot_metaspace_range(void* base, void* top) {
294     _aot_metaspace_base = base;
295     _aot_metaspace_top = top;
296   }
297 
298   static void* aot_metaspace_base() { return _aot_metaspace_base; }
299   static void* aot_metaspace_top()  { return _aot_metaspace_top;  }
300 
301 #define METASPACE_OBJ_TYPES_DO(f) \
302   f(Class) \
303   f(Symbol) \
304   f(TypeArrayU1) \
305   f(TypeArrayU2) \
306   f(TypeArrayU4) \
307   f(TypeArrayU8) \
308   f(TypeArrayOther) \
309   f(Method) \
310   f(ConstMethod) \
311   f(MethodData) \
312   f(ConstantPool) \
313   f(ConstantPoolCache) \
314   f(Annotations) \
315   f(MethodCounters) \
316   f(RecordComponent) \
317   f(KlassTrainingData) \
318   f(MethodTrainingData) \
319   f(CompileTrainingData) \
320   f(AdapterHandlerEntry) \
321   f(AdapterFingerPrint)
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 MetaspaceObj::Type array_type(size_t elem_size) {
342     switch (elem_size) {
343     case 1: return TypeArrayU1Type;
344     case 2: return TypeArrayU2Type;
345     case 4: return TypeArrayU4Type;
346     case 8: return TypeArrayU8Type;
347     default:
348       return TypeArrayOtherType;
349     }
350   }
351 
352   void* operator new(size_t size, ClassLoaderData* loader_data,
353                      size_t word_size,
354                      Type type, JavaThread* thread) throw();
355                      // can't use TRAPS from this header file.
356   void* operator new(size_t size, ClassLoaderData* loader_data,
357                      size_t word_size,
358                      Type type) throw();
359   // This is used for allocating training data. We are allocating training data in many cases where a GC cannot be triggered.
360   void* operator new(size_t size, MemTag flags);
361   void operator delete(void* p) = delete;
362 
363   // Declare a *static* method with the same signature in any subclass of MetaspaceObj
364   // that should be read-only by default. See symbol.hpp for an example. This function
365   // is used by the templates in metaspaceClosure.hpp
366   static bool is_read_only_by_default() { return false; }
367 };
368 
369 // Base class for classes that constitute name spaces.
370 
371 class Arena;
372 
373 extern char* resource_allocate_bytes(size_t size,
374     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
375 extern char* resource_allocate_bytes(Thread* thread, size_t size,
376     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
377 extern char* resource_reallocate_bytes( char *old, size_t old_size, size_t new_size,
378     AllocFailType alloc_failmode = AllocFailStrategy::EXIT_OOM);
379 extern void resource_free_bytes( Thread* thread, char *old, size_t size );
380 
381 //----------------------------------------------------------------------
382 // Base class for objects allocated in the resource area.
383 class ResourceObj {
384  public:
385   void* operator new(size_t size) {
386     return resource_allocate_bytes(size);
387   }
388 
389   void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
390     return resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
391   }
392 
393   void* operator new [](size_t size) throw() = delete;
394   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() = delete;
395 
396   void  operator delete(void* p) = delete;
397   void  operator delete [](void* p) = delete;
398 };
399 
400 class ArenaObj {
401  public:
402   void* operator new(size_t size, Arena *arena) throw();
403   void* operator new [](size_t size, Arena *arena) throw() = delete;
404 
405   void* operator new [](size_t size) throw() = delete;
406   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) throw() = delete;
407 
408   void  operator delete(void* p) = delete;
409   void  operator delete [](void* p) = delete;
410 };
411 
412 //----------------------------------------------------------------------
413 // Base class for objects allocated in the resource area per default.
414 // Optionally, objects may be allocated on the C heap with
415 // new (AnyObj::C_HEAP) Foo(...) or in an Arena with new (&arena).
416 // AnyObj's can be allocated within other objects, but don't use
417 // new or delete (allocation_type is unknown).  If new is used to allocate,
418 // use delete to deallocate.
419 class AnyObj {
420  public:
421   enum allocation_type { STACK_OR_EMBEDDED = 0, RESOURCE_AREA, C_HEAP, ARENA, allocation_mask = 0x3 };
422   static void set_allocation_type(address res, allocation_type type) NOT_DEBUG_RETURN;
423 #ifdef ASSERT
424  private:
425   // When this object is allocated on stack the new() operator is not
426   // called but garbage on stack may look like a valid allocation_type.
427   // Store negated 'this' pointer when new() is called to distinguish cases.
428   // Use second array's element for verification value to distinguish garbage.
429   uintptr_t _allocation_t[2];
430   bool is_type_set() const;
431   void initialize_allocation_info();
432  public:
433   allocation_type get_allocation_type() const;
434   bool allocated_on_stack_or_embedded() const { return get_allocation_type() == STACK_OR_EMBEDDED; }
435   bool allocated_on_res_area() const { return get_allocation_type() == RESOURCE_AREA; }
436   bool allocated_on_C_heap()   const { return get_allocation_type() == C_HEAP; }
437   bool allocated_on_arena()    const { return get_allocation_type() == ARENA; }
438 protected:
439   AnyObj(); // default constructor
440   AnyObj(const AnyObj& r); // default copy constructor
441   AnyObj& operator=(const AnyObj& r); // default copy assignment
442   ~AnyObj();
443 #endif // ASSERT
444 
445  public:
446   // CHeap allocations
447   void* operator new(size_t size, MemTag mem_tag) throw();
448   void* operator new [](size_t size, MemTag mem_tag) throw() = delete;
449   void* operator new(size_t size, const std::nothrow_t&  nothrow_constant, MemTag mem_tag) throw();
450   void* operator new [](size_t size, const std::nothrow_t&  nothrow_constant, MemTag mem_tag) throw() = delete;
451 
452   // Arena allocations
453   void* operator new(size_t size, Arena *arena);
454   void* operator new [](size_t size, Arena *arena) = delete;
455 
456   // Resource allocations
457   void* operator new(size_t size) {
458     address res = (address)resource_allocate_bytes(size);
459     DEBUG_ONLY(set_allocation_type(res, RESOURCE_AREA);)
460     return res;
461   }
462   void* operator new(size_t size, const std::nothrow_t& nothrow_constant) throw() {
463     address res = (address)resource_allocate_bytes(size, AllocFailStrategy::RETURN_NULL);
464     DEBUG_ONLY(if (res != nullptr) set_allocation_type(res, RESOURCE_AREA);)
465     return res;
466   }
467 
468   void* operator new [](size_t size) = delete;
469   void* operator new [](size_t size, const std::nothrow_t& nothrow_constant) = delete;
470   void  operator delete(void* p);
471   void  operator delete [](void* p) = delete;
472 
473 #ifndef PRODUCT
474   // Printing support
475   void print() const;
476   virtual void print_on(outputStream* st) const;
477 #endif // PRODUCT
478 };
479 
480 // One of the following macros must be used when allocating an array
481 // or object to determine whether it should reside in the C heap on in
482 // the resource area.
483 
484 #define NEW_RESOURCE_ARRAY(type, size)\
485   (type*) resource_allocate_bytes((size) * sizeof(type))
486 
487 #define NEW_RESOURCE_ARRAY_RETURN_NULL(type, size)\
488   (type*) resource_allocate_bytes((size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
489 
490 #define NEW_RESOURCE_ARRAY_IN_THREAD(thread, type, size)\
491   (type*) resource_allocate_bytes(thread, (size) * sizeof(type))
492 
493 #define NEW_RESOURCE_ARRAY_IN_THREAD_RETURN_NULL(thread, type, size)\
494   (type*) resource_allocate_bytes(thread, (size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
495 
496 #define REALLOC_RESOURCE_ARRAY(type, old, old_size, new_size)\
497   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type), (new_size) * sizeof(type))
498 
499 #define REALLOC_RESOURCE_ARRAY_RETURN_NULL(type, old, old_size, new_size)\
500   (type*) resource_reallocate_bytes((char*)(old), (old_size) * sizeof(type),\
501                                     (new_size) * sizeof(type), AllocFailStrategy::RETURN_NULL)
502 
503 #define FREE_RESOURCE_ARRAY(type, old, size)\
504   resource_free_bytes(Thread::current(), (char*)(old), (size) * sizeof(type))
505 
506 #define FREE_RESOURCE_ARRAY_IN_THREAD(thread, type, old, size)\
507   resource_free_bytes(thread, (char*)(old), (size) * sizeof(type))
508 
509 #define FREE_FAST(old)\
510     /* nop */
511 
512 #define NEW_RESOURCE_OBJ(type)\
513   NEW_RESOURCE_ARRAY(type, 1)
514 
515 #define NEW_RESOURCE_OBJ_RETURN_NULL(type)\
516   NEW_RESOURCE_ARRAY_RETURN_NULL(type, 1)
517 
518 #define NEW_C_HEAP_ARRAY3(type, size, mem_tag, pc, allocfail)\
519   (type*) AllocateHeap((size) * sizeof(type), mem_tag, pc, allocfail)
520 
521 #define NEW_C_HEAP_ARRAY2(type, size, mem_tag, pc)\
522   (type*) (AllocateHeap((size) * sizeof(type), mem_tag, pc))
523 
524 #define NEW_C_HEAP_ARRAY(type, size, mem_tag)\
525   (type*) (AllocateHeap((size) * sizeof(type), mem_tag))
526 
527 #define NEW_C_HEAP_ARRAY2_RETURN_NULL(type, size, mem_tag, pc)\
528   NEW_C_HEAP_ARRAY3(type, (size), mem_tag, pc, AllocFailStrategy::RETURN_NULL)
529 
530 #define NEW_C_HEAP_ARRAY_RETURN_NULL(type, size, mem_tag)\
531   NEW_C_HEAP_ARRAY2(type, (size), mem_tag, AllocFailStrategy::RETURN_NULL)
532 
533 #define REALLOC_C_HEAP_ARRAY(type, old, size, mem_tag)\
534   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), mem_tag))
535 
536 #define REALLOC_C_HEAP_ARRAY_RETURN_NULL(type, old, size, mem_tag)\
537   (type*) (ReallocateHeap((char*)(old), (size) * sizeof(type), mem_tag, AllocFailStrategy::RETURN_NULL))
538 
539 #define FREE_C_HEAP_ARRAY(type, old) \
540   FreeHeap((char*)(old))
541 
542 // allocate type in heap without calling ctor
543 #define NEW_C_HEAP_OBJ(type, mem_tag)\
544   NEW_C_HEAP_ARRAY(type, 1, mem_tag)
545 
546 #define NEW_C_HEAP_OBJ_RETURN_NULL(type, mem_tag)\
547   NEW_C_HEAP_ARRAY_RETURN_NULL(type, 1, mem_tag)
548 
549 // deallocate obj of type in heap without calling dtor
550 #define FREE_C_HEAP_OBJ(objname)\
551   FreeHeap((char*)objname);
552 
553 
554 //------------------------------ReallocMark---------------------------------
555 // Code which uses REALLOC_RESOURCE_ARRAY should check an associated
556 // ReallocMark, which is declared in the same scope as the reallocated
557 // pointer.  Any operation that could __potentially__ cause a reallocation
558 // should check the ReallocMark.
559 class ReallocMark: public StackObj {
560 protected:
561   NOT_PRODUCT(int _nesting;)
562 
563 public:
564   ReallocMark() PRODUCT_RETURN;
565   void check(Arena* arena = nullptr) PRODUCT_RETURN;
566 };
567 
568 // Uses mmapped memory for all allocations. All allocations are initially
569 // zero-filled. No pre-touching.
570 template <class E>
571 class MmapArrayAllocator : public AllStatic {
572  private:
573   static size_t size_for(size_t length);
574 
575  public:
576   static E* allocate_or_null(size_t length, MemTag mem_tag);
577   static E* allocate(size_t length, MemTag mem_tag);
578   static void free(E* addr, size_t length);
579 };
580 
581 // Uses malloc:ed memory for all allocations.
582 template <class E>
583 class MallocArrayAllocator : public AllStatic {
584  public:
585   static size_t size_for(size_t length);
586 
587   static E* allocate(size_t length, MemTag mem_tag);
588   static E* reallocate(E* addr, size_t new_length, MemTag mem_tag);
589   static void free(E* addr);
590 };
591 
592 #endif // SHARE_MEMORY_ALLOCATION_HPP