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diff --git a/js/public/AllocPolicy.h b/js/public/AllocPolicy.h
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+++ b/js/public/AllocPolicy.h
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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 http://mozilla.org/MPL/2.0/. */
+
+/*
+ * JS allocation policies.
+ *
+ * The allocators here are for system memory with lifetimes which are not
+ * managed by the GC. See the comment at the top of vm/MallocProvider.h.
+ */
+
+#ifndef js_AllocPolicy_h
+#define js_AllocPolicy_h
+
+#include "js/TypeDecls.h"
+#include "js/Utility.h"
+
+extern MOZ_COLD JS_PUBLIC_API void JS_ReportOutOfMemory(JSContext* cx);
+
+namespace js {
+
+class FrontendContext;
+
+enum class AllocFunction { Malloc, Calloc, Realloc };
+
+/* Base class allocation policies providing allocation methods. */
+class AllocPolicyBase {
+ public:
+  template <typename T>
+  T* maybe_pod_arena_malloc(arena_id_t arenaId, size_t numElems) {
+    return js_pod_arena_malloc<T>(arenaId, numElems);
+  }
+  template <typename T>
+  T* maybe_pod_arena_calloc(arena_id_t arenaId, size_t numElems) {
+    return js_pod_arena_calloc<T>(arenaId, numElems);
+  }
+  template <typename T>
+  T* maybe_pod_arena_realloc(arena_id_t arenaId, T* p, size_t oldSize,
+                             size_t newSize) {
+    return js_pod_arena_realloc<T>(arenaId, p, oldSize, newSize);
+  }
+  template <typename T>
+  T* pod_arena_malloc(arena_id_t arenaId, size_t numElems) {
+    return maybe_pod_arena_malloc<T>(arenaId, numElems);
+  }
+  template <typename T>
+  T* pod_arena_calloc(arena_id_t arenaId, size_t numElems) {
+    return maybe_pod_arena_calloc<T>(arenaId, numElems);
+  }
+  template <typename T>
+  T* pod_arena_realloc(arena_id_t arenaId, T* p, size_t oldSize,
+                       size_t newSize) {
+    return maybe_pod_arena_realloc<T>(arenaId, p, oldSize, newSize);
+  }
+
+  template <typename T>
+  T* maybe_pod_malloc(size_t numElems) {
+    return maybe_pod_arena_malloc<T>(js::MallocArena, numElems);
+  }
+  template <typename T>
+  T* maybe_pod_calloc(size_t numElems) {
+    return maybe_pod_arena_calloc<T>(js::MallocArena, numElems);
+  }
+  template <typename T>
+  T* maybe_pod_realloc(T* p, size_t oldSize, size_t newSize) {
+    return maybe_pod_arena_realloc<T>(js::MallocArena, p, oldSize, newSize);
+  }
+  template <typename T>
+  T* pod_malloc(size_t numElems) {
+    return pod_arena_malloc<T>(js::MallocArena, numElems);
+  }
+  template <typename T>
+  T* pod_calloc(size_t numElems) {
+    return pod_arena_calloc<T>(js::MallocArena, numElems);
+  }
+  template <typename T>
+  T* pod_realloc(T* p, size_t oldSize, size_t newSize) {
+    return pod_arena_realloc<T>(js::MallocArena, p, oldSize, newSize);
+  }
+
+  template <typename T>
+  void free_(T* p, size_t numElems = 0) {
+    js_free(p);
+  }
+};
+
+/* Policy for using system memory functions and doing no error reporting. */
+class SystemAllocPolicy : public AllocPolicyBase {
+ public:
+  void reportAllocOverflow() const {}
+  bool checkSimulatedOOM() const { return !js::oom::ShouldFailWithOOM(); }
+};
+
+MOZ_COLD JS_PUBLIC_API void ReportOutOfMemory(JSContext* cx);
+MOZ_COLD JS_PUBLIC_API void ReportOutOfMemory(FrontendContext* fc);
+
+// An out of memory condition which is easily user generatable and should
+// be specially handled to try and avoid a tab crash.
+MOZ_COLD JS_PUBLIC_API void ReportLargeOutOfMemory(JSContext* cx);
+
+/*
+ * Allocation policy that calls the system memory functions and reports errors
+ * to the context. Since the JSContext given on construction is stored for
+ * the lifetime of the container, this policy may only be used for containers
+ * whose lifetime is a shorter than the given JSContext.
+ *
+ * FIXME bug 647103 - rewrite this in terms of temporary allocation functions,
+ * not the system ones.
+ */
+class JS_PUBLIC_API TempAllocPolicy : public AllocPolicyBase {
+  // Type tag for context_bits_
+  static constexpr uintptr_t JsContextTag = 0x1;
+
+  // Either a JSContext* (if JsContextTag is set), or FrontendContext*
+  uintptr_t const context_bits_;
+
+  MOZ_ALWAYS_INLINE bool hasJSContext() const {
+    return (context_bits_ & JsContextTag) == JsContextTag;
+  }
+
+  MOZ_ALWAYS_INLINE JSContext* cx() const {
+    MOZ_ASSERT(hasJSContext());
+    return reinterpret_cast<JSContext*>(context_bits_ ^ JsContextTag);
+  }
+
+  MOZ_ALWAYS_INLINE FrontendContext* fc() const {
+    MOZ_ASSERT(!hasJSContext());
+    return reinterpret_cast<FrontendContext*>(context_bits_);
+  }
+
+  /*
+   * Non-inline helper to call JSRuntime::onOutOfMemory with minimal
+   * code bloat.
+   */
+  void* onOutOfMemory(arena_id_t arenaId, AllocFunction allocFunc,
+                      size_t nbytes, void* reallocPtr = nullptr);
+
+  template <typename T>
+  T* onOutOfMemoryTyped(arena_id_t arenaId, AllocFunction allocFunc,
+                        size_t numElems, void* reallocPtr = nullptr) {
+    size_t bytes;
+    if (MOZ_UNLIKELY(!CalculateAllocSize<T>(numElems, &bytes))) {
+      return nullptr;
+    }
+    return static_cast<T*>(
+        onOutOfMemory(arenaId, allocFunc, bytes, reallocPtr));
+  }
+
+ public:
+  MOZ_IMPLICIT TempAllocPolicy(JSContext* cx)
+      : context_bits_(uintptr_t(cx) | JsContextTag) {
+    MOZ_ASSERT((uintptr_t(cx) & JsContextTag) == 0);
+  }
+  MOZ_IMPLICIT TempAllocPolicy(FrontendContext* fc)
+      : context_bits_(uintptr_t(fc)) {
+    MOZ_ASSERT((uintptr_t(fc) & JsContextTag) == 0);
+  }
+
+  template <typename T>
+  T* pod_arena_malloc(arena_id_t arenaId, size_t numElems) {
+    T* p = this->maybe_pod_arena_malloc<T>(arenaId, numElems);
+    if (MOZ_UNLIKELY(!p)) {
+      p = onOutOfMemoryTyped<T>(arenaId, AllocFunction::Malloc, numElems);
+    }
+    return p;
+  }
+
+  template <typename T>
+  T* pod_arena_calloc(arena_id_t arenaId, size_t numElems) {
+    T* p = this->maybe_pod_arena_calloc<T>(arenaId, numElems);
+    if (MOZ_UNLIKELY(!p)) {
+      p = onOutOfMemoryTyped<T>(arenaId, AllocFunction::Calloc, numElems);
+    }
+    return p;
+  }
+
+  template <typename T>
+  T* pod_arena_realloc(arena_id_t arenaId, T* prior, size_t oldSize,
+                       size_t newSize) {
+    T* p2 = this->maybe_pod_arena_realloc<T>(arenaId, prior, oldSize, newSize);
+    if (MOZ_UNLIKELY(!p2)) {
+      p2 = onOutOfMemoryTyped<T>(arenaId, AllocFunction::Realloc, newSize,
+                                 prior);
+    }
+    return p2;
+  }
+
+  template <typename T>
+  T* pod_malloc(size_t numElems) {
+    return pod_arena_malloc<T>(js::MallocArena, numElems);
+  }
+
+  template <typename T>
+  T* pod_calloc(size_t numElems) {
+    return pod_arena_calloc<T>(js::MallocArena, numElems);
+  }
+
+  template <typename T>
+  T* pod_realloc(T* prior, size_t oldSize, size_t newSize) {
+    return pod_arena_realloc<T>(js::MallocArena, prior, oldSize, newSize);
+  }
+
+  template <typename T>
+  void free_(T* p, size_t numElems = 0) {
+    js_free(p);
+  }
+
+  void reportAllocOverflow() const;
+
+  bool checkSimulatedOOM() const {
+    if (js::oom::ShouldFailWithOOM()) {
+      if (hasJSContext()) {
+        ReportOutOfMemory(cx());
+      } else {
+        ReportOutOfMemory(fc());
+      }
+      return false;
+    }
+
+    return true;
+  }
+};
+
+/*
+ * A replacement for MallocAllocPolicy that allocates in the JS heap and adds no
+ * extra behaviours.
+ *
+ * This is currently used for allocating source buffers for parsing. Since these
+ * are temporary and will not be freed by GC, the memory is not tracked by the
+ * usual accounting.
+ */
+class MallocAllocPolicy : public AllocPolicyBase {
+ public:
+  void reportAllocOverflow() const {}
+
+  [[nodiscard]] bool checkSimulatedOOM() const { return true; }
+};
+
+} /* namespace js */
+
+#endif /* js_AllocPolicy_h */