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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
* Inline definitions of the CellAllocator methods.
* This is included from JSContext-inl.h for the definiton of JSContext::newCell
* and shouldn't need to be included elsewhere.
#ifndef gc_Allocator_inl_h
#define gc_Allocator_inl_h
#include "gc/Allocator.h"
#include "gc/Cell.h"
#include "gc/Zone.h"
#include "js/Class.h"
#include "js/RootingAPI.h"
#include "gc/Nursery-inl.h"
namespace js {
namespace gc {
template <typename T, AllowGC allowGC, typename... Args>
T* CellAllocator::NewCell(JSContext* cx, Args&&... args) {
static_assert(std::is_base_of_v<gc::Cell, T>);
// Objects. See the valid parameter list in NewObject, above.
if constexpr (std::is_base_of_v<JSObject, T>) {
return NewObject<T, allowGC>(cx, std::forward<Args>(args)...);
// BigInt
else if constexpr (std::is_base_of_v<JS::BigInt, T>) {
return NewBigInt<T, allowGC>(cx, std::forward<Args>(args)...);
// "Normal" strings (all of which can be nursery allocated). Atoms and
// external strings will fall through to the generic code below. All other
// strings go through NewString, which will forward the arguments to the
// appropriate string class's constructor.
else if constexpr (std::is_base_of_v<JSString, T> &&
!std::is_base_of_v<JSAtom, T> &&
!std::is_base_of_v<JSExternalString, T>) {
return NewString<T, allowGC>(cx, std::forward<Args>(args)...);
else {
// Allocate a new tenured GC thing that's not nursery-allocatable. Use
// cx->newCell<T>(...), where the parameters are forwarded to the type's
// constructor.
return NewTenuredCell<T, allowGC>(cx, std::forward<Args>(args)...);
template <typename T, AllowGC allowGC, typename... Args>
/* static */
T* CellAllocator::NewString(JSContext* cx, gc::Heap heap, Args&&... args) {
static_assert(std::is_base_of_v<JSString, T>);
gc::AllocKind kind = gc::MapTypeToAllocKind<T>::kind;
void* ptr = AllocNurseryOrTenuredCell<JS::TraceKind::String, allowGC>(
cx, kind, sizeof(T), heap, nullptr);
if (MOZ_UNLIKELY(!ptr)) {
return nullptr;
return new (mozilla::KnownNotNull, ptr) T(std::forward<Args>(args)...);
template <typename T, AllowGC allowGC>
/* static */
T* CellAllocator::NewBigInt(JSContext* cx, Heap heap) {
void* ptr = AllocNurseryOrTenuredCell<JS::TraceKind::BigInt, allowGC>(
cx, gc::AllocKind::BIGINT, sizeof(T), heap, nullptr);
if (MOZ_UNLIKELY(!ptr)) {
return nullptr;
return new (mozilla::KnownNotNull, ptr) T();
template <typename T, AllowGC allowGC>
/* static */
T* CellAllocator::NewObject(JSContext* cx, gc::AllocKind kind, gc::Heap heap,
const JSClass* clasp, gc::AllocSite* site) {
MOZ_ASSERT_IF(heap != gc::Heap::Tenured && clasp->hasFinalize() &&
size_t thingSize = JSObject::thingSize(kind);
void* cell = AllocNurseryOrTenuredCell<JS::TraceKind::Object, allowGC>(
cx, kind, thingSize, heap, site);
if (MOZ_UNLIKELY(!cell)) {
return nullptr;
return new (mozilla::KnownNotNull, cell) T();
template <JS::TraceKind traceKind, AllowGC allowGC>
/* static */
void* CellAllocator::AllocNurseryOrTenuredCell(JSContext* cx,
gc::AllocKind allocKind,
size_t thingSize, gc::Heap heap,
AllocSite* site) {
MOZ_ASSERT(MapAllocToTraceKind(allocKind) == traceKind);
MOZ_ASSERT(thingSize == Arena::thingSize(allocKind));
MOZ_ASSERT_IF(site && site->initialHeap() == Heap::Tenured,
heap == Heap::Tenured);
if (!PreAllocChecks<allowGC>(cx, allocKind)) {
return nullptr;
JS::Zone* zone = cx->zone();
gc::Heap minHeapToTenure = CheckedHeap(zone->minHeapToTenure(traceKind));
if (CheckedHeap(heap) < minHeapToTenure) {
if (!site) {
site = zone->unknownAllocSite(traceKind);
#ifdef JS_GC_ZEAL
site = MaybeGenerateMissingAllocSite(cx, traceKind, site);
void* ptr = cx->nursery().tryAllocateCell(site, thingSize, traceKind);
if (MOZ_LIKELY(ptr)) {
return ptr;
return RetryNurseryAlloc<allowGC>(cx, traceKind, allocKind, thingSize,
return TryNewTenuredCell<allowGC>(cx, allocKind, thingSize);
/* static */
MOZ_ALWAYS_INLINE gc::Heap CellAllocator::CheckedHeap(gc::Heap heap) {
if (heap > Heap::Tenured) {
// This helps the compiler to see that nursery allocation is never
// possible if Heap::Tenured is specified.
return heap;
template <typename T, AllowGC allowGC, typename... Args>
/* static */
T* CellAllocator::NewTenuredCell(JSContext* cx, Args&&... args) {
gc::AllocKind kind = gc::MapTypeToAllocKind<T>::kind;
void* cell = AllocTenuredCell<allowGC>(cx, kind, sizeof(T));
if (MOZ_UNLIKELY(!cell)) {
return nullptr;
return new (mozilla::KnownNotNull, cell) T(std::forward<Args>(args)...);
} // namespace gc
} // namespace js
#endif // gc_Allocator_inl_h