base/notimplemented.h

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_NOTIMPLEMENTED_H_
#define BASE_NOTIMPLEMENTED_H_

#include "base/check.h"
#include "base/dcheck_is_on.h"

// The NOTIMPLEMENTED() macro annotates codepaths which have not been
// implemented yet. If output spam is a serious concern,
// NOTIMPLEMENTED_LOG_ONCE() can be used.
#if DCHECK_IS_ON()
#define NOTIMPLEMENTED() \
  ::logging::CheckError::NotImplemented(__PRETTY_FUNCTION__)

// The lambda returns false the first time it is run, and true every other time.
// Note that the `static const bool call_once` trickery is used for thread
// safety (C++11 guarantees that `call_once` is only initialized once, no UB
// even if two threads enter concurrently).
#define NOTIMPLEMENTED_LOG_ONCE()                                      \
  switch (0)                                                           \
  case 0:                                                              \
  default:                                                             \
    if ([] {                                                           \
          bool old_value = true;                                       \
          [[maybe_unused]] static const bool call_once = [](bool* b) { \
            *b = false;                                                \
            return true;                                               \
          }(&old_value);                                               \
          return old_value;                                            \
        }())                                                           \
      ;                                                                \
    else                                                               \
      NOTIMPLEMENTED()

// The TVOS_NOT_YET_IMPLEMENTED() macro marks code paths that have not yet been
// implemented for tvOS.
#define TVOS_NOT_YET_IMPLEMENTED() \
  ::logging::CheckError::NotImplemented(__PRETTY_FUNCTION__)

#else
#define NOTIMPLEMENTED() EAT_CHECK_STREAM_PARAMS()
#define NOTIMPLEMENTED_LOG_ONCE() EAT_CHECK_STREAM_PARAMS()
#define TVOS_NOT_YET_IMPLEMENTED() EAT_CHECK_STREAM_PARAMS()
#endif

#endif  // BASE_NOTIMPLEMENTED_H_