3 files changed, 17 insertions, 10 deletions
diff --git a/absl/synchronization/internal/futex.h b/absl/synchronization/internal/futex.h
index 3539f491..06fbd6d0 100644
--- a/absl/synchronization/internal/futex.h
+++ b/absl/synchronization/internal/futex.h
@@ -38,6 +38,19 @@
 #include "absl/base/optimization.h"
 #include "absl/synchronization/internal/kernel_timeout.h"
 
+#ifdef ABSL_INTERNAL_HAVE_FUTEX
+#error ABSL_INTERNAL_HAVE_FUTEX may not be set on the command line
+#elif defined(__BIONIC__)
+// Bionic supports all the futex operations we need even when some of the futex
+// definitions are missing.
+#define ABSL_INTERNAL_HAVE_FUTEX
+#elif defined(__linux__) && defined(FUTEX_CLOCK_REALTIME)
+// FUTEX_CLOCK_REALTIME requires Linux >= 2.6.28.
+#define ABSL_INTERNAL_HAVE_FUTEX
+#endif
+
+#ifdef ABSL_INTERNAL_HAVE_FUTEX
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace synchronization_internal {
@@ -136,4 +149,6 @@ class Futex : public FutexImpl {};
 ABSL_NAMESPACE_END
 }  // namespace absl
 
+#endif  // ABSL_INTERNAL_HAVE_FUTEX
+
 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_FUTEX_H_
diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc
index c51855b0..2123be60 100644
--- a/absl/synchronization/internal/waiter.cc
+++ b/absl/synchronization/internal/waiter.cc
@@ -48,10 +48,6 @@
 #include "absl/base/optimization.h"
 #include "absl/synchronization/internal/kernel_timeout.h"
 
-#if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
-#include "absl/synchronization/internal/futex.h"
-#endif
-
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
diff --git a/absl/synchronization/internal/waiter.h b/absl/synchronization/internal/waiter.h
index 887f9b1b..be3df180 100644
--- a/absl/synchronization/internal/waiter.h
+++ b/absl/synchronization/internal/waiter.h
@@ -36,6 +36,7 @@
 #include <cstdint>
 
 #include "absl/base/internal/thread_identity.h"
+#include "absl/synchronization/internal/futex.h"
 #include "absl/synchronization/internal/kernel_timeout.h"
 
 // May be chosen at compile time via -DABSL_FORCE_WAITER_MODE=<index>
@@ -48,12 +49,7 @@
 #define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE
 #elif defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_WIN32
-#elif defined(__BIONIC__)
-// Bionic supports all the futex operations we need even when some of the futex
-// definitions are missing.
-#define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX
-#elif defined(__linux__) && defined(FUTEX_CLOCK_REALTIME)
-// FUTEX_CLOCK_REALTIME requires Linux >= 2.6.28.
+#elif defined(ABSL_INTERNAL_HAVE_FUTEX)
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX
 #elif defined(ABSL_HAVE_SEMAPHORE_H)
 #define ABSL_WAITER_MODE ABSL_WAITER_MODE_SEM