1 files changed, 52 insertions, 0 deletions
diff --git a/absl/flags/flag.cc b/absl/flags/flag.cc
new file mode 100644
index 000000000000..ba002edd24f1
--- /dev/null
+++ b/absl/flags/flag.cc
@@ -0,0 +1,52 @@
+//
+//  Copyright 2019 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 "absl/flags/flag.h"
+
+#include <cstring>
+
+namespace absl {
+
+// We want to validate the type mismatch between type definition and
+// declaration. The lock-free implementation does not allow us to do it,
+// so in debug builds we always use the slower implementation, which always
+// validates the type.
+#ifndef NDEBUG
+#define ABSL_FLAGS_ATOMIC_GET(T)                              \
+  T GetFlag(const absl::Flag<T>& flag) {                      \
+    T result;                                                 \
+    flag.internal.Read(&result, &flags_internal::FlagOps<T>); \
+    return result;                                            \
+  }
+#else
+#define ABSL_FLAGS_ATOMIC_GET(T)                                            \
+  T GetFlag(const absl::Flag<T>& flag) {                                    \
+    const int64_t r = flag.internal.atomic.load(std::memory_order_acquire); \
+    if (r != flags_internal::CommandLineFlag::kAtomicInit) {                \
+      T t;                                                                  \
+      memcpy(&t, &r, sizeof(T));                                            \
+      return t;                                                             \
+    }                                                                       \
+    T result;                                                               \
+    flag.internal.Read(&result, &flags_internal::FlagOps<T>);               \
+    return result;                                                          \
+  }
+#endif
+
+ABSL_FLAGS_INTERNAL_FOR_EACH_LOCK_FREE(ABSL_FLAGS_ATOMIC_GET)
+
+#undef ABSL_FLAGS_ATOMIC_GET
+
+}  // namespace absl