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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_ALLOCATION_H_
#define V8_ALLOCATION_H_
#include "include/v8-platform.h"
#include "src/base/compiler-specific.h"
#include "src/base/platform/platform.h"
#include "src/globals.h"
#include "src/v8.h"
namespace v8 {
namespace internal {
// This file defines memory allocation functions. If a first attempt at an
// allocation fails, these functions call back into the embedder, then attempt
// the allocation a second time. The embedder callback must not reenter V8.
// Called when allocation routines fail to allocate, even with a possible retry.
// This function should not return, but should terminate the current processing.
V8_EXPORT_PRIVATE void FatalProcessOutOfMemory(const char* message);
// Superclass for classes managed with new & delete.
class V8_EXPORT_PRIVATE Malloced {
void* operator new(size_t size) { return New(size); }
void operator delete(void* p) { Delete(p); }
static void* New(size_t size);
static void Delete(void* p);
template <typename T>
T* NewArray(size_t size) {
// operator new is already hooked up to SbMemoryAllocate, which will return
// null on failure, so on Starboard we just directly call operator new.
// Additionally Starboard platforms do not implement operator
// new(size_t, const std::no_throw&), and attempting to implement it seems to
// cause everything to break (since we also have exceptions off?).
T* result = new T[size];
T* result = new (std::nothrow) T[size];
if (result == nullptr) {
result = new T[size];
result = new (std::nothrow) T[size];
if (result == nullptr) FatalProcessOutOfMemory("NewArray");
return result;
template <typename T,
typename = typename std::enable_if<IS_TRIVIALLY_COPYABLE(T)>::type>
T* NewArray(size_t size, T default_val) {
T* result = reinterpret_cast<T*>(NewArray<uint8_t>(sizeof(T) * size));
for (size_t i = 0; i < size; ++i) result[i] = default_val;
return result;
template <typename T>
void DeleteArray(T* array) {
delete[] array;
// The normal strdup functions use malloc. These versions of StrDup
// and StrNDup uses new and calls the FatalProcessOutOfMemory handler
// if allocation fails.
V8_EXPORT_PRIVATE char* StrDup(const char* str);
char* StrNDup(const char* str, int n);
// Allocation policy for allocating in the C free store using malloc
// and free. Used as the default policy for lists.
class FreeStoreAllocationPolicy {
INLINE(void* New(size_t size)) { return Malloced::New(size); }
INLINE(static void Delete(void* p)) { Malloced::Delete(p); }
// Performs a malloc, with retry logic on failure. Returns nullptr on failure.
// Call free to release memory allocated with this function.
void* AllocWithRetry(size_t size);
void* AlignedAlloc(size_t size, size_t alignment);
void AlignedFree(void *ptr);
// Gets the page granularity for AllocatePages and FreePages. Addresses returned
// by AllocatePages and AllocatePage are aligned to this size.
V8_EXPORT_PRIVATE size_t AllocatePageSize();
// Gets the granularity at which the permissions and release calls can be made.
V8_EXPORT_PRIVATE size_t CommitPageSize();
// Sets the random seed so that GetRandomMmapAddr() will generate repeatable
// sequences of random mmap addresses.
V8_EXPORT_PRIVATE void SetRandomMmapSeed(int64_t seed);
// Generate a random address to be used for hinting allocation calls.
V8_EXPORT_PRIVATE void* GetRandomMmapAddr();
// Allocates memory. Permissions are set according to the access argument.
// |address| is a hint. |size| and |alignment| must be multiples of
// AllocatePageSize(). Returns the address of the allocated memory, with the
// specified size and alignment, or nullptr on failure.
V8_WARN_UNUSED_RESULT void* AllocatePages(void* address, size_t size,
size_t alignment,
PageAllocator::Permission access);
// Frees memory allocated by a call to AllocatePages. |address| and |size| must
// be multiples of AllocatePageSize(). Returns true on success, otherwise false.
V8_WARN_UNUSED_RESULT bool FreePages(void* address, const size_t size);
// Releases memory that is no longer needed. The range specified by |address|
// and |size| must be an allocated memory region. |size| and |new_size| must be
// multiples of CommitPageSize(). Memory from |new_size| to |size| is released.
// Released memory is left in an undefined state, so it should not be accessed.
// Returns true on success, otherwise false.
V8_WARN_UNUSED_RESULT bool ReleasePages(void* address, size_t size,
size_t new_size);
// Sets permissions according to |access|. |address| and |size| must be
// multiples of CommitPageSize(). Setting permission to kNoAccess may
// cause the memory contents to be lost. Returns true on success, otherwise
// false.
V8_WARN_UNUSED_RESULT bool SetPermissions(void* address, size_t size,
PageAllocator::Permission access);
// Convenience function that allocates a single system page with read and write
// permissions. |address| is a hint. Returns the base address of the memory and
// the page size via |allocated| on success. Returns nullptr on failure.
V8_WARN_UNUSED_RESULT byte* AllocatePage(void* address, size_t* allocated);
// Function that may release reserved memory regions to allow failed allocations
// to succeed. |length| is the amount of memory needed. Returns |true| if memory
// could be released, false otherwise.
V8_EXPORT_PRIVATE bool OnCriticalMemoryPressure(size_t length);
// Represents and controls an area of reserved memory.
class V8_EXPORT_PRIVATE VirtualMemory {
// Empty VirtualMemory object, controlling no reserved memory.
// Reserves virtual memory containing an area of the given size that is
// aligned per alignment. This may not be at the position returned by
// address().
VirtualMemory(size_t size, void* hint, size_t alignment = AllocatePageSize());
// Construct a virtual memory by assigning it some already mapped address
// and size.
VirtualMemory(void* address, size_t size) : address_(address), size_(size) {}
// Releases the reserved memory, if any, controlled by this VirtualMemory
// object.
// Returns whether the memory has been reserved.
bool IsReserved() const { return address_ != nullptr; }
// Initialize or resets an embedded VirtualMemory object.
void Reset();
// Returns the start address of the reserved memory.
// If the memory was reserved with an alignment, this address is not
// necessarily aligned. The user might need to round it up to a multiple of
// the alignment to get the start of the aligned block.
void* address() const {
return address_;
void* end() const {
return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(address_) +
// Returns the size of the reserved memory. The returned value is only
// meaningful when IsReserved() returns true.
// If the memory was reserved with an alignment, this size may be larger
// than the requested size.
size_t size() const { return size_; }
// Sets permissions according to the access argument. address and size must be
// multiples of CommitPageSize(). Returns true on success, otherwise false.
bool SetPermissions(void* address, size_t size,
PageAllocator::Permission access);
// Releases memory after |free_start|. Returns the number of bytes released.
size_t Release(void* free_start);
// Frees all memory.
void Free();
// Assign control of the reserved region to a different VirtualMemory object.
// The old object is no longer functional (IsReserved() returns false).
void TakeControl(VirtualMemory* from);
bool InVM(void* address, size_t size) {
return (reinterpret_cast<uintptr_t>(address_) <=
reinterpret_cast<uintptr_t>(address)) &&
((reinterpret_cast<uintptr_t>(address_) + size_) >=
(reinterpret_cast<uintptr_t>(address) + size));
void* address_; // Start address of the virtual memory.
size_t size_; // Size of the virtual memory.
bool AllocVirtualMemory(size_t size, void* hint, VirtualMemory* result);
bool AlignedAllocVirtualMemory(size_t size, size_t alignment, void* hint,
VirtualMemory* result);
} // namespace internal
} // namespace v8
#endif // V8_ALLOCATION_H_