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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.
+//
+
+// Some of our malloc implementations can invoke the following hooks whenever
+// memory is allocated or deallocated.  MallocHook is thread-safe, and things
+// you do before calling AddFooHook(MyHook) are visible to any resulting calls
+// to MyHook.  Hooks must be thread-safe.  If you write:
+//
+//   CHECK(MallocHook::AddNewHook(&MyNewHook));
+//
+// MyNewHook will be invoked in subsequent calls in the current thread, but
+// there are no guarantees on when it might be invoked in other threads.
+//
+// There are a limited number of slots available for each hook type.  Add*Hook
+// will return false if there are no slots available.  Remove*Hook will return
+// false if the given hook was not already installed.
+//
+// The order in which individual hooks are called in Invoke*Hook is undefined.
+//
+// It is safe for a hook to remove itself within Invoke*Hook and add other
+// hooks.  Any hooks added inside a hook invocation (for the same hook type)
+// will not be invoked for the current invocation.
+//
+// One important user of these hooks is the heap profiler.
+//
+// CAVEAT: If you add new MallocHook::Invoke* calls then those calls must be
+// directly in the code of the (de)allocation function that is provided to the
+// user and that function must have an ABSL_ATTRIBUTE_SECTION(malloc_hook)
+// attribute.
+//
+// Note: the Invoke*Hook() functions are defined in malloc_hook-inl.h.  If you
+// need to invoke a hook (which you shouldn't unless you're part of tcmalloc),
+// be sure to #include malloc_hook-inl.h in addition to malloc_hook.h.
+//
+// NOTE FOR C USERS: If you want to use malloc_hook functionality from
+// a C program, #include malloc_hook_c.h instead of this file.
+//
+// IWYU pragma: private, include "base/malloc_hook.h"
+
+#ifndef ABSL_BASE_INTERNAL_MALLOC_HOOK_H_
+#define ABSL_BASE_INTERNAL_MALLOC_HOOK_H_
+
+#include <sys/types.h>
+#include <cstddef>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/malloc_hook_c.h"
+#include "absl/base/port.h"
+
+namespace absl {
+namespace base_internal {
+
+// Note: malloc_hook_c.h defines MallocHook_*Hook and
+// MallocHook_{Add,Remove}*Hook.  The version of these inside the MallocHook
+// class are defined in terms of the malloc_hook_c version.  See malloc_hook_c.h
+// for details of these types/functions.
+
+class MallocHook {
+ public:
+  // The NewHook is invoked whenever an object is being allocated.
+  // Object pointer and size are passed in.
+  // It may be passed null pointer if the allocator returned null.
+  typedef MallocHook_NewHook NewHook;
+  inline static bool AddNewHook(NewHook hook) {
+    return MallocHook_AddNewHook(hook);
+  }
+  inline static bool RemoveNewHook(NewHook hook) {
+    return MallocHook_RemoveNewHook(hook);
+  }
+  inline static void InvokeNewHook(const void* ptr, size_t size);
+
+  // The DeleteHook is invoked whenever an object is being deallocated.
+  // Object pointer is passed in.
+  // It may be passed null pointer if the caller is trying to delete null.
+  typedef MallocHook_DeleteHook DeleteHook;
+  inline static bool AddDeleteHook(DeleteHook hook) {
+    return MallocHook_AddDeleteHook(hook);
+  }
+  inline static bool RemoveDeleteHook(DeleteHook hook) {
+    return MallocHook_RemoveDeleteHook(hook);
+  }
+  inline static void InvokeDeleteHook(const void* ptr);
+
+  // The SampledNewHook is invoked for some subset of object allocations
+  // according to the sampling policy of an allocator such as tcmalloc.
+  // SampledAlloc has the following fields:
+  //  * AllocHandle handle: to be set to an effectively unique value (in this
+  //    process) by allocator.
+  //  * size_t allocated_size: space actually used by allocator to host
+  //    the object.
+  //  * int stack_depth and const void* stack: invocation stack for
+  //    the allocation.
+  // The allocator invoking the hook should record the handle value and later
+  // call InvokeSampledDeleteHook() with that value.
+  typedef MallocHook_SampledNewHook SampledNewHook;
+  typedef MallocHook_SampledAlloc SampledAlloc;
+  inline static bool AddSampledNewHook(SampledNewHook hook) {
+    return MallocHook_AddSampledNewHook(hook);
+  }
+  inline static bool RemoveSampledNewHook(SampledNewHook hook) {
+    return MallocHook_RemoveSampledNewHook(hook);
+  }
+  inline static void InvokeSampledNewHook(const SampledAlloc* sampled_alloc);
+
+  // The SampledDeleteHook is invoked whenever an object previously chosen
+  // by an allocator for sampling is being deallocated.
+  // The handle identifying the object --as previously chosen by
+  // InvokeSampledNewHook()-- is passed in.
+  typedef MallocHook_SampledDeleteHook SampledDeleteHook;
+  typedef MallocHook_AllocHandle AllocHandle;
+  inline static bool AddSampledDeleteHook(SampledDeleteHook hook) {
+    return MallocHook_AddSampledDeleteHook(hook);
+  }
+  inline static bool RemoveSampledDeleteHook(SampledDeleteHook hook) {
+    return MallocHook_RemoveSampledDeleteHook(hook);
+  }
+  inline static void InvokeSampledDeleteHook(AllocHandle handle);
+
+  // The PreMmapHook is invoked with mmap's or mmap64's arguments just
+  // before the mmap/mmap64 call is actually made.  Such a hook may be useful
+  // in memory limited contexts, to catch allocations that will exceed
+  // a memory limit, and take outside actions to increase that limit.
+  typedef MallocHook_PreMmapHook PreMmapHook;
+  inline static bool AddPreMmapHook(PreMmapHook hook) {
+    return MallocHook_AddPreMmapHook(hook);
+  }
+  inline static bool RemovePreMmapHook(PreMmapHook hook) {
+    return MallocHook_RemovePreMmapHook(hook);
+  }
+  inline static void InvokePreMmapHook(const void* start,
+                                       size_t size,
+                                       int protection,
+                                       int flags,
+                                       int fd,
+                                       off_t offset);
+
+  // The MmapReplacement is invoked with mmap's arguments and place to put the
+  // result into after the PreMmapHook but before the mmap/mmap64 call is
+  // actually made.
+  // The MmapReplacement should return true if it handled the call, or false
+  // if it is still necessary to call mmap/mmap64.
+  // This should be used only by experts, and users must be be
+  // extremely careful to avoid recursive calls to mmap. The replacement
+  // should be async signal safe.
+  // Only one MmapReplacement is supported. After setting an MmapReplacement
+  // you must call RemoveMmapReplacement before calling SetMmapReplacement
+  // again.
+  typedef MallocHook_MmapReplacement MmapReplacement;
+  inline static bool SetMmapReplacement(MmapReplacement hook) {
+    return MallocHook_SetMmapReplacement(hook);
+  }
+  inline static bool RemoveMmapReplacement(MmapReplacement hook) {
+    return MallocHook_RemoveMmapReplacement(hook);
+  }
+  inline static bool InvokeMmapReplacement(const void* start,
+                                           size_t size,
+                                           int protection,
+                                           int flags,
+                                           int fd,
+                                           off_t offset,
+                                           void** result);
+
+
+  // The MmapHook is invoked with mmap's return value and arguments whenever
+  // a region of memory has been just mapped.
+  // It may be passed MAP_FAILED if the mmap failed.
+  typedef MallocHook_MmapHook MmapHook;
+  inline static bool AddMmapHook(MmapHook hook) {
+    return MallocHook_AddMmapHook(hook);
+  }
+  inline static bool RemoveMmapHook(MmapHook hook) {
+    return MallocHook_RemoveMmapHook(hook);
+  }
+  inline static void InvokeMmapHook(const void* result,
+                                    const void* start,
+                                    size_t size,
+                                    int protection,
+                                    int flags,
+                                    int fd,
+                                    off_t offset);
+
+  // The MunmapReplacement is invoked with munmap's arguments and place to put
+  // the result into just before the munmap call is actually made.
+  // The MunmapReplacement should return true if it handled the call, or false
+  // if it is still necessary to call munmap.
+  // This should be used only by experts. The replacement should be
+  // async signal safe.
+  // Only one MunmapReplacement is supported. After setting an
+  // MunmapReplacement you must call RemoveMunmapReplacement before
+  // calling SetMunmapReplacement again.
+  typedef MallocHook_MunmapReplacement MunmapReplacement;
+  inline static bool SetMunmapReplacement(MunmapReplacement hook) {
+    return MallocHook_SetMunmapReplacement(hook);
+  }
+  inline static bool RemoveMunmapReplacement(MunmapReplacement hook) {
+    return MallocHook_RemoveMunmapReplacement(hook);
+  }
+  inline static bool InvokeMunmapReplacement(const void* start,
+                                             size_t size,
+                                             int* result);
+
+  // The MunmapHook is invoked with munmap's arguments just before the munmap
+  // call is actually made.
+  // TODO(maxim): Rename this to PreMunmapHook for consistency with PreMmapHook
+  // and PreSbrkHook.
+  typedef MallocHook_MunmapHook MunmapHook;
+  inline static bool AddMunmapHook(MunmapHook hook) {
+    return MallocHook_AddMunmapHook(hook);
+  }
+  inline static bool RemoveMunmapHook(MunmapHook hook) {
+    return MallocHook_RemoveMunmapHook(hook);
+  }
+  inline static void InvokeMunmapHook(const void* start, size_t size);
+
+  // The MremapHook is invoked with mremap's return value and arguments
+  // whenever a region of memory has been just remapped.
+  typedef MallocHook_MremapHook MremapHook;
+  inline static bool AddMremapHook(MremapHook hook) {
+    return MallocHook_AddMremapHook(hook);
+  }
+  inline static bool RemoveMremapHook(MremapHook hook) {
+    return MallocHook_RemoveMremapHook(hook);
+  }
+  inline static void InvokeMremapHook(const void* result,
+                                      const void* old_addr,
+                                      size_t old_size,
+                                      size_t new_size,
+                                      int flags,
+                                      const void* new_addr);
+
+  // The PreSbrkHook is invoked with sbrk's argument just before sbrk is called
+  // -- except when the increment is 0.  This is because sbrk(0) is often called
+  // to get the top of the memory stack, and is not actually a
+  // memory-allocation call.  It may be useful in memory-limited contexts,
+  // to catch allocations that will exceed the limit and take outside
+  // actions to increase such a limit.
+  typedef MallocHook_PreSbrkHook PreSbrkHook;
+  inline static bool AddPreSbrkHook(PreSbrkHook hook) {
+    return MallocHook_AddPreSbrkHook(hook);
+  }
+  inline static bool RemovePreSbrkHook(PreSbrkHook hook) {
+    return MallocHook_RemovePreSbrkHook(hook);
+  }
+  inline static void InvokePreSbrkHook(ptrdiff_t increment);
+
+  // The SbrkHook is invoked with sbrk's result and argument whenever sbrk
+  // has just executed -- except when the increment is 0.
+  // This is because sbrk(0) is often called to get the top of the memory stack,
+  // and is not actually a memory-allocation call.
+  typedef MallocHook_SbrkHook SbrkHook;
+  inline static bool AddSbrkHook(SbrkHook hook) {
+    return MallocHook_AddSbrkHook(hook);
+  }
+  inline static bool RemoveSbrkHook(SbrkHook hook) {
+    return MallocHook_RemoveSbrkHook(hook);
+  }
+  inline static void InvokeSbrkHook(const void* result, ptrdiff_t increment);
+
+  // Pointer to a absl::GetStackTrace implementation, following the API in
+  // base/stacktrace.h.
+  using GetStackTraceFn = int (*)(void**, int, int);
+
+  // Get the current stack trace.  Try to skip all routines up to and
+  // including the caller of MallocHook::Invoke*.
+  // Use "skip_count" (similarly to absl::GetStackTrace from stacktrace.h)
+  // as a hint about how many routines to skip if better information
+  // is not available.
+  // Stack trace is filled into *result up to the size of max_depth.
+  // The actual number of stack frames filled is returned.
+  inline static int GetCallerStackTrace(void** result, int max_depth,
+                                        int skip_count,
+                                        GetStackTraceFn get_stack_trace_fn) {
+    return MallocHook_GetCallerStackTrace(result, max_depth, skip_count,
+                                          get_stack_trace_fn);
+  }
+
+#if ABSL_HAVE_MMAP
+  // Unhooked versions of mmap() and munmap().   These should be used
+  // only by experts, since they bypass heapchecking, etc.
+  // Note: These do not run hooks, but they still use the MmapReplacement
+  // and MunmapReplacement.
+  static void* UnhookedMMap(void* start, size_t size, int protection, int flags,
+                            int fd, off_t offset);
+  static int UnhookedMUnmap(void* start, size_t size);
+#endif
+
+ private:
+  // Slow path versions of Invoke*Hook.
+  static void InvokeNewHookSlow(const void* ptr,
+                                size_t size) ABSL_ATTRIBUTE_COLD;
+  static void InvokeDeleteHookSlow(const void* ptr) ABSL_ATTRIBUTE_COLD;
+  static void InvokeSampledNewHookSlow(const SampledAlloc* sampled_alloc)
+      ABSL_ATTRIBUTE_COLD;
+  static void InvokeSampledDeleteHookSlow(AllocHandle handle)
+      ABSL_ATTRIBUTE_COLD;
+  static void InvokePreMmapHookSlow(const void* start, size_t size,
+                                    int protection, int flags, int fd,
+                                    off_t offset) ABSL_ATTRIBUTE_COLD;
+  static void InvokeMmapHookSlow(const void* result, const void* start,
+                                 size_t size, int protection, int flags, int fd,
+                                 off_t offset) ABSL_ATTRIBUTE_COLD;
+  static bool InvokeMmapReplacementSlow(const void* start, size_t size,
+                                        int protection, int flags, int fd,
+                                        off_t offset,
+                                        void** result) ABSL_ATTRIBUTE_COLD;
+  static void InvokeMunmapHookSlow(const void* ptr,
+                                   size_t size) ABSL_ATTRIBUTE_COLD;
+  static bool InvokeMunmapReplacementSlow(const void* ptr, size_t size,
+                                          int* result) ABSL_ATTRIBUTE_COLD;
+  static void InvokeMremapHookSlow(const void* result, const void* old_addr,
+                                   size_t old_size, size_t new_size, int flags,
+                                   const void* new_addr) ABSL_ATTRIBUTE_COLD;
+  static void InvokePreSbrkHookSlow(ptrdiff_t increment) ABSL_ATTRIBUTE_COLD;
+  static void InvokeSbrkHookSlow(const void* result,
+                                 ptrdiff_t increment) ABSL_ATTRIBUTE_COLD;
+};
+
+}  // namespace base_internal
+}  // namespace absl
+#endif  // ABSL_BASE_INTERNAL_MALLOC_HOOK_H_