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diff --git a/absl/base/internal/malloc_hook_invoke.h b/absl/base/internal/malloc_hook_invoke.h
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+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+///
+
+// This has the implementation details of malloc_hook that are needed
+// to use malloc-hook inside the tcmalloc system.  It does not hold
+// any of the client-facing calls that are used to add new hooks.
+//
+// IWYU pragma: private, include "base/malloc_hook-inl.h"
+
+#ifndef ABSL_BASE_INTERNAL_MALLOC_HOOK_INVOKE_H_
+#define ABSL_BASE_INTERNAL_MALLOC_HOOK_INVOKE_H_
+
+#include <sys/types.h>
+#include <atomic>
+#include <cstddef>
+
+#include "absl/base/internal/malloc_hook.h"
+
+namespace absl {
+namespace base_internal {
+
+// Maximum of 7 hooks means that HookList is 8 words.
+static constexpr int kHookListMaxValues = 7;
+
+// HookList: a class that provides synchronized insertions and removals and
+// lockless traversal.  Most of the implementation is in malloc_hook.cc.
+template <typename T>
+struct HookList {
+  static_assert(sizeof(T) <= sizeof(intptr_t), "T_should_fit_in_intptr_t");
+
+  // Adds value to the list.  Note that duplicates are allowed.  Thread-safe and
+  // blocking (acquires hooklist_spinlock).  Returns true on success; false
+  // otherwise (failures include invalid value and no space left).
+  bool Add(T value);
+
+  // Removes the first entry matching value from the list.  Thread-safe and
+  // blocking (acquires hooklist_spinlock).  Returns true on success; false
+  // otherwise (failures include invalid value and no value found).
+  bool Remove(T value);
+
+  // Store up to n values of the list in output_array, and return the number of
+  // elements stored.  Thread-safe and non-blocking.  This is fast (one memory
+  // access) if the list is empty.
+  int Traverse(T* output_array, int n) const;
+
+  // Fast inline implementation for fast path of Invoke*Hook.
+  bool empty() const {
+    // empty() is only used as an optimization to determine if we should call
+    // Traverse which has proper acquire loads.  Memory reordering around a
+    // call to empty will either lead to an unnecessary Traverse call, or will
+    // miss invoking hooks, neither of which is a problem.
+    return priv_end.load(std::memory_order_relaxed) == 0;
+  }
+
+  // This internal data is not private so that the class is an aggregate and can
+  // be initialized by the linker.  Don't access this directly.  Use the
+  // INIT_HOOK_LIST macro in malloc_hook.cc.
+
+  // One more than the index of the last valid element in priv_data.  During
+  // 'Remove' this may be past the last valid element in priv_data, but
+  // subsequent values will be 0.
+  std::atomic<int> priv_end;
+  std::atomic<intptr_t> priv_data[kHookListMaxValues];
+};
+
+extern template struct HookList<MallocHook::NewHook>;
+
+extern HookList<MallocHook::NewHook> new_hooks_;
+extern HookList<MallocHook::DeleteHook> delete_hooks_;
+extern HookList<MallocHook::SampledNewHook> sampled_new_hooks_;
+extern HookList<MallocHook::SampledDeleteHook> sampled_delete_hooks_;
+extern HookList<MallocHook::PreMmapHook> premmap_hooks_;
+extern HookList<MallocHook::MmapHook> mmap_hooks_;
+extern HookList<MallocHook::MmapReplacement> mmap_replacement_;
+extern HookList<MallocHook::MunmapHook> munmap_hooks_;
+extern HookList<MallocHook::MunmapReplacement> munmap_replacement_;
+extern HookList<MallocHook::MremapHook> mremap_hooks_;
+extern HookList<MallocHook::PreSbrkHook> presbrk_hooks_;
+extern HookList<MallocHook::SbrkHook> sbrk_hooks_;
+
+inline void MallocHook::InvokeNewHook(const void* ptr, size_t size) {
+  if (!absl::base_internal::new_hooks_.empty()) {
+    InvokeNewHookSlow(ptr, size);
+  }
+}
+
+inline void MallocHook::InvokeDeleteHook(const void* ptr) {
+  if (!absl::base_internal::delete_hooks_.empty()) {
+    InvokeDeleteHookSlow(ptr);
+  }
+}
+
+inline void MallocHook::InvokeSampledNewHook(
+    const SampledAlloc* sampled_alloc) {
+  if (!absl::base_internal::sampled_new_hooks_.empty()) {
+    InvokeSampledNewHookSlow(sampled_alloc);
+  }
+}
+
+inline void MallocHook::InvokeSampledDeleteHook(AllocHandle handle) {
+  if (!absl::base_internal::sampled_delete_hooks_.empty()) {
+    InvokeSampledDeleteHookSlow(handle);
+  }
+}
+
+inline void MallocHook::InvokePreMmapHook(const void* start,
+                                          size_t size,
+                                          int protection,
+                                          int flags,
+                                          int fd,
+                                          off_t offset) {
+  if (!absl::base_internal::premmap_hooks_.empty()) {
+    InvokePreMmapHookSlow(start, size, protection, flags, fd, offset);
+  }
+}
+
+inline void MallocHook::InvokeMmapHook(const void* result,
+                                       const void* start,
+                                       size_t size,
+                                       int protection,
+                                       int flags,
+                                       int fd,
+                                       off_t offset) {
+  if (!absl::base_internal::mmap_hooks_.empty()) {
+    InvokeMmapHookSlow(result, start, size, protection, flags, fd, offset);
+  }
+}
+
+inline bool MallocHook::InvokeMmapReplacement(const void* start,
+                                              size_t size,
+                                              int protection,
+                                              int flags,
+                                              int fd,
+                                              off_t offset,
+                                              void** result) {
+  if (!absl::base_internal::mmap_replacement_.empty()) {
+    return InvokeMmapReplacementSlow(start, size,
+                                     protection, flags,
+                                     fd, offset,
+                                     result);
+  }
+  return false;
+}
+
+inline void MallocHook::InvokeMunmapHook(const void* start, size_t size) {
+  if (!absl::base_internal::munmap_hooks_.empty()) {
+    InvokeMunmapHookSlow(start, size);
+  }
+}
+
+inline bool MallocHook::InvokeMunmapReplacement(
+    const void* start, size_t size, int* result) {
+  if (!absl::base_internal::mmap_replacement_.empty()) {
+    return InvokeMunmapReplacementSlow(start, size, result);
+  }
+  return false;
+}
+
+inline void MallocHook::InvokeMremapHook(const void* result,
+                                         const void* old_addr,
+                                         size_t old_size,
+                                         size_t new_size,
+                                         int flags,
+                                         const void* new_addr) {
+  if (!absl::base_internal::mremap_hooks_.empty()) {
+    InvokeMremapHookSlow(result, old_addr, old_size, new_size, flags, new_addr);
+  }
+}
+
+inline void MallocHook::InvokePreSbrkHook(ptrdiff_t increment) {
+  if (!absl::base_internal::presbrk_hooks_.empty() && increment != 0) {
+    InvokePreSbrkHookSlow(increment);
+  }
+}
+
+inline void MallocHook::InvokeSbrkHook(const void* result,
+                                       ptrdiff_t increment) {
+  if (!absl::base_internal::sbrk_hooks_.empty() && increment != 0) {
+    InvokeSbrkHookSlow(result, increment);
+  }
+}
+
+}  // namespace base_internal
+}  // namespace absl
+#endif  // ABSL_BASE_INTERNAL_MALLOC_HOOK_INVOKE_H_