diff --git a/absl/base/dynamic_annotations.cc b/absl/base/dynamic_annotations.cc
new file mode 100644
index 0000000..21e822e
--- /dev/null
+++ b/absl/base/dynamic_annotations.cc
@@ -0,0 +1,129 @@
+// 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
+//
+//      https://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.
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "absl/base/dynamic_annotations.h"
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
+/* Compiler-based ThreadSanitizer defines
+   DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL = 1
+   and provides its own definitions of the functions. */
+
+#ifndef DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL
+# define DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL 0
+#endif
+
+/* Each function is empty and called (via a macro) only in debug mode.
+   The arguments are captured by dynamic tools at runtime. */
+
+#if DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL == 0 && !defined(__native_client__)
+
+#if __has_feature(memory_sanitizer)
+#include <sanitizer/msan_interface.h>
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void AnnotateRWLockCreate(const char *, int,
+                          const volatile void *){}
+void AnnotateRWLockDestroy(const char *, int,
+                           const volatile void *){}
+void AnnotateRWLockAcquired(const char *, int,
+                            const volatile void *, long){}
+void AnnotateRWLockReleased(const char *, int,
+                            const volatile void *, long){}
+void AnnotateBenignRace(const char *, int,
+                        const volatile void *,
+                        const char *){}
+void AnnotateBenignRaceSized(const char *, int,
+                             const volatile void *,
+                             size_t,
+                             const char *) {}
+void AnnotateThreadName(const char *, int,
+                        const char *){}
+void AnnotateIgnoreReadsBegin(const char *, int){}
+void AnnotateIgnoreReadsEnd(const char *, int){}
+void AnnotateIgnoreWritesBegin(const char *, int){}
+void AnnotateIgnoreWritesEnd(const char *, int){}
+void AnnotateEnableRaceDetection(const char *, int, int){}
+void AnnotateMemoryIsInitialized(const char *, int,
+                                 const volatile void *mem, size_t size) {
+#if __has_feature(memory_sanitizer)
+  __msan_unpoison(mem, size);
+#else
+  (void)mem;
+  (void)size;
+#endif
+}
+
+void AnnotateMemoryIsUninitialized(const char *, int,
+                                   const volatile void *mem, size_t size) {
+#if __has_feature(memory_sanitizer)
+  __msan_allocated_memory(mem, size);
+#else
+  (void)mem;
+  (void)size;
+#endif
+}
+
+static int GetRunningOnValgrind(void) {
+#ifdef RUNNING_ON_VALGRIND
+  if (RUNNING_ON_VALGRIND) return 1;
+#endif
+  char *running_on_valgrind_str = getenv("RUNNING_ON_VALGRIND");
+  if (running_on_valgrind_str) {
+    return strcmp(running_on_valgrind_str, "0") != 0;
+  }
+  return 0;
+}
+
+/* See the comments in dynamic_annotations.h */
+int RunningOnValgrind(void) {
+  static volatile int running_on_valgrind = -1;
+  int local_running_on_valgrind = running_on_valgrind;
+  /* C doesn't have thread-safe initialization of statics, and we
+     don't want to depend on pthread_once here, so hack it. */
+  ANNOTATE_BENIGN_RACE(&running_on_valgrind, "safe hack");
+  if (local_running_on_valgrind == -1)
+    running_on_valgrind = local_running_on_valgrind = GetRunningOnValgrind();
+  return local_running_on_valgrind;
+}
+
+/* See the comments in dynamic_annotations.h */
+double ValgrindSlowdown(void) {
+  /* Same initialization hack as in RunningOnValgrind(). */
+  static volatile double slowdown = 0.0;
+  double local_slowdown = slowdown;
+  ANNOTATE_BENIGN_RACE(&slowdown, "safe hack");
+  if (RunningOnValgrind() == 0) {
+    return 1.0;
+  }
+  if (local_slowdown == 0.0) {
+    char *env = getenv("VALGRIND_SLOWDOWN");
+    slowdown = local_slowdown = env ? atof(env) : 50.0;
+  }
+  return local_slowdown;
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+#endif  /* DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL == 0 */