path: root/absl/flags/flag.cc

//
//  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