Replace a DCHECK with static_assert

webrtc/modules/audio_processing/audio_processing_impl.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 52 matching lines @@
 #define RETURN_ON_ERR(expr) \
   do {                      \
     int err = (expr);       \
     if (err != kNoError) {  \
       return err;           \
     }                       \
   } while (0)
 
 namespace webrtc {
 
-const int AudioProcessing::kNativeSampleRatesHz[] = {
-    AudioProcessing::kSampleRate8kHz,
-    AudioProcessing::kSampleRate16kHz,
-    AudioProcessing::kSampleRate32kHz,
-    AudioProcessing::kSampleRate48kHz};
-const size_t AudioProcessing::kNumNativeSampleRates =
-    arraysize(AudioProcessing::kNativeSampleRatesHz);
-const int AudioProcessing::kMaxNativeSampleRateHz = AudioProcessing::
-    kNativeSampleRatesHz[AudioProcessing::kNumNativeSampleRates - 1];
+constexpr int AudioProcessing::kNativeSampleRatesHz[];
 
 namespace {
 
 static bool LayoutHasKeyboard(AudioProcessing::ChannelLayout layout) {
   switch (layout) {
     case AudioProcessing::kMono:
     case AudioProcessing::kStereo:
       return false;
     case AudioProcessing::kMonoAndKeyboard:
     case AudioProcessing::kStereoAndKeyboard:
       return true;
   }
 
   assert(false);
   return false;
 }
 
 bool SampleRateSupportsMultiBand(int sample_rate_hz) {
   return sample_rate_hz == AudioProcessing::kSampleRate32kHz ||
          sample_rate_hz == AudioProcessing::kSampleRate48kHz;
 }
 
 int FindNativeProcessRateToUse(int minimum_rate, bool band_splitting_required) {
 #ifdef WEBRTC_ARCH_ARM_FAMILY
-  const int kMaxSplittingNativeProcessRate = AudioProcessing::kSampleRate32kHz;
+  constexpr int kMaxSplittingNativeProcessRate =
+      AudioProcessing::kSampleRate32kHz;
 #else
-  const int kMaxSplittingNativeProcessRate = AudioProcessing::kSampleRate48kHz;
+  constexpr int kMaxSplittingNativeProcessRate =
+      AudioProcessing::kSampleRate48kHz;
 #endif
-  RTC_DCHECK_LE(kMaxSplittingNativeProcessRate,
-                AudioProcessing::kMaxNativeSampleRateHz);
+  static_assert(
+      kMaxSplittingNativeProcessRate <= AudioProcessing::kMaxNativeSampleRateHz,
+      "");

[peah-webrtc, 2016/09/13 12:50:12]

Don't we want a message for the assert?

[kwiberg-webrtc, 2016/09/13 13:11:17]

No. If the assert fails, there'll be a compilation error that points to this
source line---that's enough. The second argument to static_assert is almost
never useful. (And indeed, in C++17 you're allowed to omit it.)

   const int uppermost_native_rate = band_splitting_required
                                         ? kMaxSplittingNativeProcessRate
                                         : AudioProcessing::kSampleRate48kHz;
 
   for (auto rate : AudioProcessing::kNativeSampleRatesHz) {
     if (rate >= uppermost_native_rate) {
       return uppermost_native_rate;
     }
     if (rate >= minimum_rate) {
       return rate;
@@ skipping 1476 matching lines @@
       fwd_proc_format(kSampleRate16kHz),
       split_rate(kSampleRate16kHz) {}
 
 AudioProcessingImpl::ApmCaptureState::~ApmCaptureState() = default;
 
 AudioProcessingImpl::ApmRenderState::ApmRenderState() = default;
 
 AudioProcessingImpl::ApmRenderState::~ApmRenderState() = default;
 
 }  // namespace webrtc