Internal change

PiperOrigin-RevId: 424113966
google · Jan 25, 2022 · 945af7a · 945af7a
1 parent 1d0d6eb
commit 945af7a
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Showing 2 changed files with 24 additions and 7 deletions.
diff --git a/yggdrasil_decision_forests/utils/BUILD b/yggdrasil_decision_forests/utils/BUILD
@@ -308,6 +308,15 @@ cc_library_ydf(
         "//yggdrasil_decision_forests:std_synchronization_primitives": [
             "YGG_STD_MUTEX",
             "YGG_STD_BLOCKING_COUNTER_AND_NOTIFICATION",
+            # When YGG_STD_MUTEX and YGG_STD_BLOCKING_COUNTER_AND_NOTIFICATION are set,
+            # this build rule relies on c++17 and c++20 primitives (see the comments in
+            # synchronization_primitives.h). However, this rule can effectively be compiled with
+            # c++14 using a modern enought compiler with availabilities disabled (done by defining
+            # _LIBCPP_DISABLE_AVAILABILITY).
+            #
+            # See:
+            # https://releases.llvm.org/3.1/tools/clang/docs/LanguageExtensions.html#availability
+            "_LIBCPP_DISABLE_AVAILABILITY",
         ],
         "//conditions:default": [],
     }),

diff --git a/yggdrasil_decision_forests/utils/synchronization_primitives.h b/yggdrasil_decision_forests/utils/synchronization_primitives.h
@@ -24,7 +24,7 @@
 #ifdef YGG_STD_MUTEX
 #include <condition_variable>  // c++11
 #include <mutex>               // c++11
-#include <shared_mutex>        // c++17
+#include <shared_mutex>        // c++14 and c++17
 #else
 #include "absl/synchronization/mutex.h"
 #endif
@@ -41,6 +41,14 @@ namespace utils {
 namespace concurrency {
 
 #ifdef YGG_STD_MUTEX
+
+#if _LIBCPP_STD_VER >= 17
+// shared_mutex was introduced in c++17.
+using std_shared_mutex = std::shared_mutex;
+#else
+using std_shared_mutex = std::shared_timed_mutex;
+#endif
+
 class Mutex {
  public:
   std::mutex& std() { return mu_; }
@@ -51,10 +59,10 @@ class Mutex {
 
 class SharedMutex {
  public:
-  std::shared_mutex& std() { return mu_; }
+  std_shared_mutex& std() { return mu_; }
 
  private:
-  std::shared_mutex mu_;
+  std_shared_mutex mu_;
 };
 
 class MutexLock {
@@ -69,19 +77,19 @@ class MutexLock {
 class WriterMutexLock {
  public:
   WriterMutexLock(SharedMutex* mutex) : lock_(mutex->std()) {}
-  std::unique_lock<std::shared_mutex>& std() { return lock_; }
+  std::unique_lock<std_shared_mutex>& std() { return lock_; }
 
  private:
-  std::unique_lock<std::shared_mutex> lock_;
+  std::unique_lock<std_shared_mutex> lock_;
 };
 
 class ReaderMutexLock {
  public:
   ReaderMutexLock(SharedMutex* mutex) : lock_(mutex->std()) {}
-  std::shared_lock<std::shared_mutex>& std() { return lock_; }
+  std::shared_lock<std_shared_mutex>& std() { return lock_; }
 
  private:
-  std::shared_lock<std::shared_mutex> lock_;
+  std::shared_lock<std_shared_mutex> lock_;
 };
 
 class CondVar {