Vendor import of stripped compiler-rt trunk r375505, the last commitvendor/compiler-rt/compiler-rt-trunk-r375505vendor/compiler-rt

before the upstream Subversion repository was made read-only, and the
LLVM project migrated to GitHub:

https://llvm.org/svn/llvm-project/compiler-rt/trunk@375505

1 files changed, 519 insertions, 0 deletions

diff --git a/lib/tsan/rtl/tsan_interceptors_mac.cpp b/lib/tsan/rtl/tsan_interceptors_mac.cpp
new file mode 100644
index 000000000000..aa29536d8616
--- /dev/null
+++ b/lib/tsan/rtl/tsan_interceptors_mac.cpp
@@ -0,0 +1,519 @@
+//===-- tsan_interceptors_mac.cpp -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of ThreadSanitizer (TSan), a race detector.
+//
+// Mac-specific interceptors.
+//===----------------------------------------------------------------------===//
+
+#include "sanitizer_common/sanitizer_platform.h"
+#if SANITIZER_MAC
+
+#include "interception/interception.h"
+#include "tsan_interceptors.h"
+#include "tsan_interface.h"
+#include "tsan_interface_ann.h"
+#include "sanitizer_common/sanitizer_addrhashmap.h"
+
+#include <errno.h>
+#include <libkern/OSAtomic.h>
+#include <objc/objc-sync.h>
+#include <os/lock.h>
+#include <sys/ucontext.h>
+
+#if defined(__has_include) && __has_include(<xpc/xpc.h>)
+#include <xpc/xpc.h>
+#endif  // #if defined(__has_include) && __has_include(<xpc/xpc.h>)
+
+typedef long long_t;
+
+extern "C" {
+int getcontext(ucontext_t *ucp) __attribute__((returns_twice));
+int setcontext(const ucontext_t *ucp);
+}
+
+namespace __tsan {
+
+// The non-barrier versions of OSAtomic* functions are semantically mo_relaxed,
+// but the two variants (e.g. OSAtomicAdd32 and OSAtomicAdd32Barrier) are
+// actually aliases of each other, and we cannot have different interceptors for
+// them, because they're actually the same function.  Thus, we have to stay
+// conservative and treat the non-barrier versions as mo_acq_rel.
+static const morder kMacOrderBarrier = mo_acq_rel;
+static const morder kMacOrderNonBarrier = mo_acq_rel;
+
+#define OSATOMIC_INTERCEPTOR(return_t, t, tsan_t, f, tsan_atomic_f, mo) \
+  TSAN_INTERCEPTOR(return_t, f, t x, volatile t *ptr) {                 \
+    SCOPED_TSAN_INTERCEPTOR(f, x, ptr);                                 \
+    return tsan_atomic_f((volatile tsan_t *)ptr, x, mo);                \
+  }
+
+#define OSATOMIC_INTERCEPTOR_PLUS_X(return_t, t, tsan_t, f, tsan_atomic_f, mo) \
+  TSAN_INTERCEPTOR(return_t, f, t x, volatile t *ptr) {                        \
+    SCOPED_TSAN_INTERCEPTOR(f, x, ptr);                                        \
+    return tsan_atomic_f((volatile tsan_t *)ptr, x, mo) + x;                   \
+  }
+
+#define OSATOMIC_INTERCEPTOR_PLUS_1(return_t, t, tsan_t, f, tsan_atomic_f, mo) \
+  TSAN_INTERCEPTOR(return_t, f, volatile t *ptr) {                             \
+    SCOPED_TSAN_INTERCEPTOR(f, ptr);                                           \
+    return tsan_atomic_f((volatile tsan_t *)ptr, 1, mo) + 1;                   \
+  }
+
+#define OSATOMIC_INTERCEPTOR_MINUS_1(return_t, t, tsan_t, f, tsan_atomic_f, \
+                                     mo)                                    \
+  TSAN_INTERCEPTOR(return_t, f, volatile t *ptr) {                          \
+    SCOPED_TSAN_INTERCEPTOR(f, ptr);                                        \
+    return tsan_atomic_f((volatile tsan_t *)ptr, 1, mo) - 1;                \
+  }
+
+#define OSATOMIC_INTERCEPTORS_ARITHMETIC(f, tsan_atomic_f, m)                  \
+  m(int32_t, int32_t, a32, f##32, __tsan_atomic32_##tsan_atomic_f,             \
+    kMacOrderNonBarrier)                                                       \
+  m(int32_t, int32_t, a32, f##32##Barrier, __tsan_atomic32_##tsan_atomic_f,    \
+    kMacOrderBarrier)                                                          \
+  m(int64_t, int64_t, a64, f##64, __tsan_atomic64_##tsan_atomic_f,             \
+    kMacOrderNonBarrier)                                                       \
+  m(int64_t, int64_t, a64, f##64##Barrier, __tsan_atomic64_##tsan_atomic_f,    \
+    kMacOrderBarrier)
+
+#define OSATOMIC_INTERCEPTORS_BITWISE(f, tsan_atomic_f, m, m_orig)             \
+  m(int32_t, uint32_t, a32, f##32, __tsan_atomic32_##tsan_atomic_f,            \
+    kMacOrderNonBarrier)                                                       \
+  m(int32_t, uint32_t, a32, f##32##Barrier, __tsan_atomic32_##tsan_atomic_f,   \
+    kMacOrderBarrier)                                                          \
+  m_orig(int32_t, uint32_t, a32, f##32##Orig, __tsan_atomic32_##tsan_atomic_f, \
+    kMacOrderNonBarrier)                                                       \
+  m_orig(int32_t, uint32_t, a32, f##32##OrigBarrier,                           \
+    __tsan_atomic32_##tsan_atomic_f, kMacOrderBarrier)
+
+OSATOMIC_INTERCEPTORS_ARITHMETIC(OSAtomicAdd, fetch_add,
+                                 OSATOMIC_INTERCEPTOR_PLUS_X)
+OSATOMIC_INTERCEPTORS_ARITHMETIC(OSAtomicIncrement, fetch_add,
+                                 OSATOMIC_INTERCEPTOR_PLUS_1)
+OSATOMIC_INTERCEPTORS_ARITHMETIC(OSAtomicDecrement, fetch_sub,
+                                 OSATOMIC_INTERCEPTOR_MINUS_1)
+OSATOMIC_INTERCEPTORS_BITWISE(OSAtomicOr, fetch_or, OSATOMIC_INTERCEPTOR_PLUS_X,
+                              OSATOMIC_INTERCEPTOR)
+OSATOMIC_INTERCEPTORS_BITWISE(OSAtomicAnd, fetch_and,
+                              OSATOMIC_INTERCEPTOR_PLUS_X, OSATOMIC_INTERCEPTOR)
+OSATOMIC_INTERCEPTORS_BITWISE(OSAtomicXor, fetch_xor,
+                              OSATOMIC_INTERCEPTOR_PLUS_X, OSATOMIC_INTERCEPTOR)
+
+#define OSATOMIC_INTERCEPTORS_CAS(f, tsan_atomic_f, tsan_t, t)              \
+  TSAN_INTERCEPTOR(bool, f, t old_value, t new_value, t volatile *ptr) {    \
+    SCOPED_TSAN_INTERCEPTOR(f, old_value, new_value, ptr);                  \
+    return tsan_atomic_f##_compare_exchange_strong(                         \
+        (volatile tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value,    \
+        kMacOrderNonBarrier, kMacOrderNonBarrier);                          \
+  }                                                                         \
+                                                                            \
+  TSAN_INTERCEPTOR(bool, f##Barrier, t old_value, t new_value,              \
+                   t volatile *ptr) {                                       \
+    SCOPED_TSAN_INTERCEPTOR(f##Barrier, old_value, new_value, ptr);         \
+    return tsan_atomic_f##_compare_exchange_strong(                         \
+        (volatile tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value,    \
+        kMacOrderBarrier, kMacOrderNonBarrier);                             \
+  }
+
+OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwapInt, __tsan_atomic32, a32, int)
+OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwapLong, __tsan_atomic64, a64,
+                          long_t)
+OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwapPtr, __tsan_atomic64, a64,
+                          void *)
+OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwap32, __tsan_atomic32, a32,
+                          int32_t)
+OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwap64, __tsan_atomic64, a64,
+                          int64_t)
+
+#define OSATOMIC_INTERCEPTOR_BITOP(f, op, clear, mo)             \
+  TSAN_INTERCEPTOR(bool, f, uint32_t n, volatile void *ptr) {    \
+    SCOPED_TSAN_INTERCEPTOR(f, n, ptr);                          \
+    volatile char *byte_ptr = ((volatile char *)ptr) + (n >> 3); \
+    char bit = 0x80u >> (n & 7);                                 \
+    char mask = clear ? ~bit : bit;                              \
+    char orig_byte = op((volatile a8 *)byte_ptr, mask, mo);      \
+    return orig_byte & bit;                                      \
+  }
+
+#define OSATOMIC_INTERCEPTORS_BITOP(f, op, clear)               \
+  OSATOMIC_INTERCEPTOR_BITOP(f, op, clear, kMacOrderNonBarrier) \
+  OSATOMIC_INTERCEPTOR_BITOP(f##Barrier, op, clear, kMacOrderBarrier)
+
+OSATOMIC_INTERCEPTORS_BITOP(OSAtomicTestAndSet, __tsan_atomic8_fetch_or, false)
+OSATOMIC_INTERCEPTORS_BITOP(OSAtomicTestAndClear, __tsan_atomic8_fetch_and,
+                            true)
+
+TSAN_INTERCEPTOR(void, OSAtomicEnqueue, OSQueueHead *list, void *item,
+                 size_t offset) {
+  SCOPED_TSAN_INTERCEPTOR(OSAtomicEnqueue, list, item, offset);
+  __tsan_release(item);
+  REAL(OSAtomicEnqueue)(list, item, offset);
+}
+
+TSAN_INTERCEPTOR(void *, OSAtomicDequeue, OSQueueHead *list, size_t offset) {
+  SCOPED_TSAN_INTERCEPTOR(OSAtomicDequeue, list, offset);
+  void *item = REAL(OSAtomicDequeue)(list, offset);
+  if (item) __tsan_acquire(item);
+  return item;
+}
+
+// OSAtomicFifoEnqueue and OSAtomicFifoDequeue are only on OS X.
+#if !SANITIZER_IOS
+
+TSAN_INTERCEPTOR(void, OSAtomicFifoEnqueue, OSFifoQueueHead *list, void *item,
+                 size_t offset) {
+  SCOPED_TSAN_INTERCEPTOR(OSAtomicFifoEnqueue, list, item, offset);
+  __tsan_release(item);
+  REAL(OSAtomicFifoEnqueue)(list, item, offset);
+}
+
+TSAN_INTERCEPTOR(void *, OSAtomicFifoDequeue, OSFifoQueueHead *list,
+                 size_t offset) {
+  SCOPED_TSAN_INTERCEPTOR(OSAtomicFifoDequeue, list, offset);
+  void *item = REAL(OSAtomicFifoDequeue)(list, offset);
+  if (item) __tsan_acquire(item);
+  return item;
+}
+
+#endif
+
+TSAN_INTERCEPTOR(void, OSSpinLockLock, volatile OSSpinLock *lock) {
+  CHECK(!cur_thread()->is_dead);
+  if (!cur_thread()->is_inited) {
+    return REAL(OSSpinLockLock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(OSSpinLockLock, lock);
+  REAL(OSSpinLockLock)(lock);
+  Acquire(thr, pc, (uptr)lock);
+}
+
+TSAN_INTERCEPTOR(bool, OSSpinLockTry, volatile OSSpinLock *lock) {
+  CHECK(!cur_thread()->is_dead);
+  if (!cur_thread()->is_inited) {
+    return REAL(OSSpinLockTry)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(OSSpinLockTry, lock);
+  bool result = REAL(OSSpinLockTry)(lock);
+  if (result)
+    Acquire(thr, pc, (uptr)lock);
+  return result;
+}
+
+TSAN_INTERCEPTOR(void, OSSpinLockUnlock, volatile OSSpinLock *lock) {
+  CHECK(!cur_thread()->is_dead);
+  if (!cur_thread()->is_inited) {
+    return REAL(OSSpinLockUnlock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(OSSpinLockUnlock, lock);
+  Release(thr, pc, (uptr)lock);
+  REAL(OSSpinLockUnlock)(lock);
+}
+
+TSAN_INTERCEPTOR(void, os_lock_lock, void *lock) {
+  CHECK(!cur_thread()->is_dead);
+  if (!cur_thread()->is_inited) {
+    return REAL(os_lock_lock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_lock_lock, lock);
+  REAL(os_lock_lock)(lock);
+  Acquire(thr, pc, (uptr)lock);
+}
+
+TSAN_INTERCEPTOR(bool, os_lock_trylock, void *lock) {
+  CHECK(!cur_thread()->is_dead);
+  if (!cur_thread()->is_inited) {
+    return REAL(os_lock_trylock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_lock_trylock, lock);
+  bool result = REAL(os_lock_trylock)(lock);
+  if (result)
+    Acquire(thr, pc, (uptr)lock);
+  return result;
+}
+
+TSAN_INTERCEPTOR(void, os_lock_unlock, void *lock) {
+  CHECK(!cur_thread()->is_dead);
+  if (!cur_thread()->is_inited) {
+    return REAL(os_lock_unlock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_lock_unlock, lock);
+  Release(thr, pc, (uptr)lock);
+  REAL(os_lock_unlock)(lock);
+}
+
+TSAN_INTERCEPTOR(void, os_unfair_lock_lock, os_unfair_lock_t lock) {
+  if (!cur_thread()->is_inited || cur_thread()->is_dead) {
+    return REAL(os_unfair_lock_lock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_unfair_lock_lock, lock);
+  REAL(os_unfair_lock_lock)(lock);
+  Acquire(thr, pc, (uptr)lock);
+}
+
+TSAN_INTERCEPTOR(void, os_unfair_lock_lock_with_options, os_unfair_lock_t lock,
+                 u32 options) {
+  if (!cur_thread()->is_inited || cur_thread()->is_dead) {
+    return REAL(os_unfair_lock_lock_with_options)(lock, options);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_unfair_lock_lock_with_options, lock, options);
+  REAL(os_unfair_lock_lock_with_options)(lock, options);
+  Acquire(thr, pc, (uptr)lock);
+}
+
+TSAN_INTERCEPTOR(bool, os_unfair_lock_trylock, os_unfair_lock_t lock) {
+  if (!cur_thread()->is_inited || cur_thread()->is_dead) {
+    return REAL(os_unfair_lock_trylock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_unfair_lock_trylock, lock);
+  bool result = REAL(os_unfair_lock_trylock)(lock);
+  if (result)
+    Acquire(thr, pc, (uptr)lock);
+  return result;
+}
+
+TSAN_INTERCEPTOR(void, os_unfair_lock_unlock, os_unfair_lock_t lock) {
+  if (!cur_thread()->is_inited || cur_thread()->is_dead) {
+    return REAL(os_unfair_lock_unlock)(lock);
+  }
+  SCOPED_TSAN_INTERCEPTOR(os_unfair_lock_unlock, lock);
+  Release(thr, pc, (uptr)lock);
+  REAL(os_unfair_lock_unlock)(lock);
+}
+
+#if defined(__has_include) && __has_include(<xpc/xpc.h>)
+
+TSAN_INTERCEPTOR(void, xpc_connection_set_event_handler,
+                 xpc_connection_t connection, xpc_handler_t handler) {
+  SCOPED_TSAN_INTERCEPTOR(xpc_connection_set_event_handler, connection,
+                          handler);
+  Release(thr, pc, (uptr)connection);
+  xpc_handler_t new_handler = ^(xpc_object_t object) {
+    {
+      SCOPED_INTERCEPTOR_RAW(xpc_connection_set_event_handler);
+      Acquire(thr, pc, (uptr)connection);
+    }
+    handler(object);
+  };
+  REAL(xpc_connection_set_event_handler)(connection, new_handler);
+}
+
+TSAN_INTERCEPTOR(void, xpc_connection_send_barrier, xpc_connection_t connection,
+                 dispatch_block_t barrier) {
+  SCOPED_TSAN_INTERCEPTOR(xpc_connection_send_barrier, connection, barrier);
+  Release(thr, pc, (uptr)connection);
+  dispatch_block_t new_barrier = ^() {
+    {
+      SCOPED_INTERCEPTOR_RAW(xpc_connection_send_barrier);
+      Acquire(thr, pc, (uptr)connection);
+    }
+    barrier();
+  };
+  REAL(xpc_connection_send_barrier)(connection, new_barrier);
+}
+
+TSAN_INTERCEPTOR(void, xpc_connection_send_message_with_reply,
+                 xpc_connection_t connection, xpc_object_t message,
+                 dispatch_queue_t replyq, xpc_handler_t handler) {
+  SCOPED_TSAN_INTERCEPTOR(xpc_connection_send_message_with_reply, connection,
+                          message, replyq, handler);
+  Release(thr, pc, (uptr)connection);
+  xpc_handler_t new_handler = ^(xpc_object_t object) {
+    {
+      SCOPED_INTERCEPTOR_RAW(xpc_connection_send_message_with_reply);
+      Acquire(thr, pc, (uptr)connection);
+    }
+    handler(object);
+  };
+  REAL(xpc_connection_send_message_with_reply)
+  (connection, message, replyq, new_handler);
+}
+
+TSAN_INTERCEPTOR(void, xpc_connection_cancel, xpc_connection_t connection) {
+  SCOPED_TSAN_INTERCEPTOR(xpc_connection_cancel, connection);
+  Release(thr, pc, (uptr)connection);
+  REAL(xpc_connection_cancel)(connection);
+}
+
+#endif  // #if defined(__has_include) && __has_include(<xpc/xpc.h>)
+
+// Determines whether the Obj-C object pointer is a tagged pointer. Tagged
+// pointers encode the object data directly in their pointer bits and do not
+// have an associated memory allocation. The Obj-C runtime uses tagged pointers
+// to transparently optimize small objects.
+static bool IsTaggedObjCPointer(id obj) {
+  const uptr kPossibleTaggedBits = 0x8000000000000001ull;
+  return ((uptr)obj & kPossibleTaggedBits) != 0;
+}
+
+// Returns an address which can be used to inform TSan about synchronization
+// points (MutexLock/Unlock). The TSan infrastructure expects this to be a valid
+// address in the process space. We do a small allocation here to obtain a
+// stable address (the array backing the hash map can change). The memory is
+// never free'd (leaked) and allocation and locking are slow, but this code only
+// runs for @synchronized with tagged pointers, which is very rare.
+static uptr GetOrCreateSyncAddress(uptr addr, ThreadState *thr, uptr pc) {
+  typedef AddrHashMap<uptr, 5> Map;
+  static Map Addresses;
+  Map::Handle h(&Addresses, addr);
+  if (h.created()) {
+    ThreadIgnoreBegin(thr, pc);
+    *h = (uptr) user_alloc(thr, pc, /*size=*/1);
+    ThreadIgnoreEnd(thr, pc);
+  }
+  return *h;
+}
+
+// Returns an address on which we can synchronize given an Obj-C object pointer.
+// For normal object pointers, this is just the address of the object in memory.
+// Tagged pointers are not backed by an actual memory allocation, so we need to
+// synthesize a valid address.
+static uptr SyncAddressForObjCObject(id obj, ThreadState *thr, uptr pc) {
+  if (IsTaggedObjCPointer(obj))
+    return GetOrCreateSyncAddress((uptr)obj, thr, pc);
+  return (uptr)obj;
+}
+
+TSAN_INTERCEPTOR(int, objc_sync_enter, id obj) {
+  SCOPED_TSAN_INTERCEPTOR(objc_sync_enter, obj);
+  if (!obj) return REAL(objc_sync_enter)(obj);
+  uptr addr = SyncAddressForObjCObject(obj, thr, pc);
+  MutexPreLock(thr, pc, addr, MutexFlagWriteReentrant);
+  int result = REAL(objc_sync_enter)(obj);
+  CHECK_EQ(result, OBJC_SYNC_SUCCESS);
+  MutexPostLock(thr, pc, addr, MutexFlagWriteReentrant);
+  return result;
+}
+
+TSAN_INTERCEPTOR(int, objc_sync_exit, id obj) {
+  SCOPED_TSAN_INTERCEPTOR(objc_sync_exit, obj);
+  if (!obj) return REAL(objc_sync_exit)(obj);
+  uptr addr = SyncAddressForObjCObject(obj, thr, pc);
+  MutexUnlock(thr, pc, addr);
+  int result = REAL(objc_sync_exit)(obj);
+  if (result != OBJC_SYNC_SUCCESS) MutexInvalidAccess(thr, pc, addr);
+  return result;
+}
+
+TSAN_INTERCEPTOR(int, swapcontext, ucontext_t *oucp, const ucontext_t *ucp) {
+  {
+    SCOPED_INTERCEPTOR_RAW(swapcontext, oucp, ucp);
+  }
+  // Bacause of swapcontext() semantics we have no option but to copy its
+  // impementation here
+  if (!oucp || !ucp) {
+    errno = EINVAL;
+    return -1;
+  }
+  ThreadState *thr = cur_thread();
+  const int UCF_SWAPPED = 0x80000000;
+  oucp->uc_onstack &= ~UCF_SWAPPED;
+  thr->ignore_interceptors++;
+  int ret = getcontext(oucp);
+  if (!(oucp->uc_onstack & UCF_SWAPPED)) {
+    thr->ignore_interceptors--;
+    if (!ret) {
+      oucp->uc_onstack |= UCF_SWAPPED;
+      ret = setcontext(ucp);
+    }
+  }
+  return ret;
+}
+
+// On macOS, libc++ is always linked dynamically, so intercepting works the
+// usual way.
+#define STDCXX_INTERCEPTOR TSAN_INTERCEPTOR
+
+namespace {
+struct fake_shared_weak_count {
+  volatile a64 shared_owners;
+  volatile a64 shared_weak_owners;
+  virtual void _unused_0x0() = 0;
+  virtual void _unused_0x8() = 0;
+  virtual void on_zero_shared() = 0;
+  virtual void _unused_0x18() = 0;
+  virtual void on_zero_shared_weak() = 0;
+};
+}  // namespace
+
+// The following code adds libc++ interceptors for:
+//     void __shared_weak_count::__release_shared() _NOEXCEPT;
+//     bool __shared_count::__release_shared() _NOEXCEPT;
+// Shared and weak pointers in C++ maintain reference counts via atomics in
+// libc++.dylib, which are TSan-invisible, and this leads to false positives in
+// destructor code. These interceptors re-implements the whole functions so that
+// the mo_acq_rel semantics of the atomic decrement are visible.
+//
+// Unfortunately, the interceptors cannot simply Acquire/Release some sync
+// object and call the original function, because it would have a race between
+// the sync and the destruction of the object.  Calling both under a lock will
+// not work because the destructor can invoke this interceptor again (and even
+// in a different thread, so recursive locks don't help).
+
+STDCXX_INTERCEPTOR(void, _ZNSt3__119__shared_weak_count16__release_sharedEv,
+                   fake_shared_weak_count *o) {
+  if (!flags()->shared_ptr_interceptor)
+    return REAL(_ZNSt3__119__shared_weak_count16__release_sharedEv)(o);
+
+  SCOPED_TSAN_INTERCEPTOR(_ZNSt3__119__shared_weak_count16__release_sharedEv,
+                          o);
+  if (__tsan_atomic64_fetch_add(&o->shared_owners, -1, mo_release) == 0) {
+    Acquire(thr, pc, (uptr)&o->shared_owners);
+    o->on_zero_shared();
+    if (__tsan_atomic64_fetch_add(&o->shared_weak_owners, -1, mo_release) ==
+        0) {
+      Acquire(thr, pc, (uptr)&o->shared_weak_owners);
+      o->on_zero_shared_weak();
+    }
+  }
+}
+
+STDCXX_INTERCEPTOR(bool, _ZNSt3__114__shared_count16__release_sharedEv,
+                   fake_shared_weak_count *o) {
+  if (!flags()->shared_ptr_interceptor)
+    return REAL(_ZNSt3__114__shared_count16__release_sharedEv)(o);
+
+  SCOPED_TSAN_INTERCEPTOR(_ZNSt3__114__shared_count16__release_sharedEv, o);
+  if (__tsan_atomic64_fetch_add(&o->shared_owners, -1, mo_release) == 0) {
+    Acquire(thr, pc, (uptr)&o->shared_owners);
+    o->on_zero_shared();
+    return true;
+  }
+  return false;
+}
+
+namespace {
+struct call_once_callback_args {
+  void (*orig_func)(void *arg);
+  void *orig_arg;
+  void *flag;
+};
+
+void call_once_callback_wrapper(void *arg) {
+  call_once_callback_args *new_args = (call_once_callback_args *)arg;
+  new_args->orig_func(new_args->orig_arg);
+  __tsan_release(new_args->flag);
+}
+}  // namespace
+
+// This adds a libc++ interceptor for:
+//     void __call_once(volatile unsigned long&, void*, void(*)(void*));
+// C++11 call_once is implemented via an internal function __call_once which is
+// inside libc++.dylib, and the atomic release store inside it is thus
+// TSan-invisible. To avoid false positives, this interceptor wraps the callback
+// function and performs an explicit Release after the user code has run.
+STDCXX_INTERCEPTOR(void, _ZNSt3__111__call_onceERVmPvPFvS2_E, void *flag,
+                   void *arg, void (*func)(void *arg)) {
+  call_once_callback_args new_args = {func, arg, flag};
+  REAL(_ZNSt3__111__call_onceERVmPvPFvS2_E)(flag, &new_args,
+                                            call_once_callback_wrapper);
+}
+
+}  // namespace __tsan
+
+#endif  // SANITIZER_MAC