Disallow implicit fallthrough (#26874)

Most instances were already explicit through comments, so it's clear that the author cared about being explicit; use the compiler to ensure this is always the case.
4 years ago · ccad567e0b
parent ce483be968
commit ccad567e0b
22 changed files with 69 additions and 54 deletions
--- a/6
+++ b/6
@ -694,11 +694,12 @@ grpc_cc_library(
    ],
    external_deps = [
        "absl/base",
+        "absl/base:core_headers",
        "absl/memory",
        "absl/status",
        "absl/strings",
-        "absl/strings:str_format",
        "absl/strings:cord",
+        "absl/strings:str_format",
        "absl/synchronization",
        "absl/time:time",
        "absl/types:optional",
@ -2536,10 +2537,11 @@ grpc_cc_library(
        "src/core/ext/transport/chttp2/transport/varint.h",
    ],
    external_deps = [
+        "absl/base:core_headers",
        "absl/memory",
        "absl/status",
-        "absl/strings:str_format",
        "absl/strings",
+        "absl/strings:str_format",
    ],
    language = "c++",
    visibility = ["@grpc:grpclb"],
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -1437,6 +1437,7 @@ target_include_directories(gpr
 target_link_libraries(gpr
  ${_gRPC_ALLTARGETS_LIBRARIES}
  absl::base
+  absl::core_headers
  absl::memory
  absl::status
  absl::cord
@ -16051,7 +16052,7 @@ generate_pkgconfig(
  "gpr"
  "gRPC platform support library"
  "${gRPC_CORE_VERSION}"
-  "absl_base absl_cord absl_memory absl_optional absl_status absl_str_format absl_strings absl_synchronization absl_time"
+  "absl_base absl_cord absl_core_headers absl_memory absl_optional absl_status absl_str_format absl_strings absl_synchronization absl_time"
  "-lgpr"
  ""
  "gpr.pc")
@ -16061,7 +16062,7 @@ generate_pkgconfig(
  "gRPC"
  "high performance general RPC framework"
  "${gRPC_CORE_VERSION}"
-  "gpr openssl absl_base absl_bind_front absl_cord absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
+  "gpr openssl absl_base absl_bind_front absl_cord absl_core_headers absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
  "-lgrpc -laddress_sorting -lre2 -lupb -lcares -lz"
  ""
  "grpc.pc")
@ -16071,7 +16072,7 @@ generate_pkgconfig(
  "gRPC unsecure"
  "high performance general RPC framework without SSL"
  "${gRPC_CORE_VERSION}"
-  "gpr absl_base absl_bind_front absl_cord absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
+  "gpr absl_base absl_bind_front absl_cord absl_core_headers absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
  "-lgrpc_unsecure"
  ""
  "grpc_unsecure.pc")
@ -16081,7 +16082,7 @@ generate_pkgconfig(
  "gRPC++"
  "C++ wrapper for gRPC"
  "${gRPC_CPP_VERSION}"
-  "grpc absl_base absl_bind_front absl_cord absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
+  "grpc absl_base absl_bind_front absl_cord absl_core_headers absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
  "-lgrpc++"
  ""
  "grpc++.pc")
@ -16091,7 +16092,7 @@ generate_pkgconfig(
  "gRPC++ unsecure"
  "C++ wrapper for gRPC without SSL"
  "${gRPC_CPP_VERSION}"
-  "grpc_unsecure absl_base absl_bind_front absl_cord absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
+  "grpc_unsecure absl_base absl_bind_front absl_cord absl_core_headers absl_flat_hash_map absl_inlined_vector absl_memory absl_optional absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time"
  "-lgrpc++_unsecure"
  ""
  "grpc++_unsecure.pc")
--- a/bazel/copts.bzl
+++ b/bazel/copts.bzl
@ -14,9 +14,11 @@

 # This is a list of llvm flags to be used when being built with use_strict_warning=1
 GRPC_LLVM_WARNING_FLAGS = [
-    # Enable all & extra waninrgs
+    # Enable all & extra warnings
    "-Wall",
    "-Wextra",
+    # Avoid some known traps
+    "-Wimplicit-fallthrough",
    # Consider warnings as errors
    "-Werror",
    # Ignore unknown warning flags
--- a/build_autogenerated.yaml
+++ b/build_autogenerated.yaml
@ -393,6 +393,7 @@ libs:
  - src/core/lib/profiling/stap_timers.cc
  deps:
  - absl/base:base
+  - absl/base:core_headers
  - absl/memory:memory
  - absl/status:status
  - absl/strings:cord
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@ -189,6 +189,7 @@ Pod::Spec.new do |s|
    ss.dependency 'gRPC-Core', version
    abseil_version = '1.20210324.0'
    ss.dependency 'abseil/base/base', abseil_version
+    ss.dependency 'abseil/base/core_headers', abseil_version
    ss.dependency 'abseil/container/flat_hash_map', abseil_version
    ss.dependency 'abseil/container/inlined_vector', abseil_version
    ss.dependency 'abseil/functional/bind_front', abseil_version
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@ -179,6 +179,7 @@ Pod::Spec.new do |s|
    ss.dependency "#{s.name}/Interface", version
    ss.dependency 'BoringSSL-GRPC', '0.0.19'
    ss.dependency 'abseil/base/base', abseil_version
+    ss.dependency 'abseil/base/core_headers', abseil_version
    ss.dependency 'abseil/container/flat_hash_map', abseil_version
    ss.dependency 'abseil/container/inlined_vector', abseil_version
    ss.dependency 'abseil/functional/bind_front', abseil_version
--- a/grpc.gyp
+++ b/grpc.gyp
@ -395,6 +395,7 @@
      'type': 'static_library',
      'dependencies': [
        'absl/base:base',
+        'absl/base:core_headers',
        'absl/memory:memory',
        'absl/status:status',
        'absl/strings:cord',
--- a/src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
@ -428,7 +428,7 @@ RingHash::PickResult RingHash::Picker::Pick(PickArgs args) {
      return PickResult::Complete(ring_[first_index].subchannel);
    case GRPC_CHANNEL_IDLE:
      ScheduleSubchannelConnectionAttempt(ring_[first_index].subchannel);
-      // fallthrough
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHANNEL_CONNECTING:
      return PickResult::Queue();
    default:  // GRPC_CHANNEL_TRANSIENT_FAILURE
@ -452,7 +452,7 @@ RingHash::PickResult RingHash::Picker::Pick(PickArgs args) {
      switch (entry.connectivity_state) {
        case GRPC_CHANNEL_IDLE:
          ScheduleSubchannelConnectionAttempt(entry.subchannel);
-          // fallthrough
+          ABSL_FALLTHROUGH_INTENDED;
        case GRPC_CHANNEL_CONNECTING:
          return PickResult::Queue();
        default:
--- a/src/core/ext/transport/chttp2/transport/bin_decoder.cc
+++ b/src/core/ext/transport/chttp2/transport/bin_decoder.cc
@ -146,7 +146,7 @@ bool grpc_base64_decode_partial(struct grpc_base64_decode_context* ctx) {
      switch (input_tail) {
        case 3:
          ctx->output_cur[1] = COMPOSE_OUTPUT_BYTE_1(ctx->input_cur);
-        /* fallthrough */
+          ABSL_FALLTHROUGH_INTENDED;
        case 2:
          ctx->output_cur[0] = COMPOSE_OUTPUT_BYTE_0(ctx->input_cur);
      }
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
@ -2444,7 +2444,7 @@ static void WithUrgency(grpc_chttp2_transport* t,
      break;
    case grpc_core::chttp2::FlowControlAction::Urgency::UPDATE_IMMEDIATELY:
      grpc_chttp2_initiate_write(t, reason);
-    // fallthrough
+      ABSL_FALLTHROUGH_INTENDED;
    case grpc_core::chttp2::FlowControlAction::Urgency::QUEUE_UPDATE:
      action();
      break;
--- a/src/core/ext/transport/chttp2/transport/frame_data.cc
+++ b/src/core/ext/transport/chttp2/transport/frame_data.cc
@ -148,7 +148,7 @@ grpc_error_handle grpc_deframe_unprocessed_incoming_frames(
          grpc_slice_buffer_remove_first(slices);
          continue;
        }
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_DATA_FH_1:
        s->stats.incoming.framing_bytes++;
        p->frame_size = (static_cast<uint32_t>(*cur)) << 24;
@ -157,7 +157,7 @@ grpc_error_handle grpc_deframe_unprocessed_incoming_frames(
          grpc_slice_buffer_remove_first(slices);
          continue;
        }
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_DATA_FH_2:
        s->stats.incoming.framing_bytes++;
        p->frame_size |= (static_cast<uint32_t>(*cur)) << 16;
@ -166,7 +166,7 @@ grpc_error_handle grpc_deframe_unprocessed_incoming_frames(
          grpc_slice_buffer_remove_first(slices);
          continue;
        }
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_DATA_FH_3:
        s->stats.incoming.framing_bytes++;
        p->frame_size |= (static_cast<uint32_t>(*cur)) << 8;
@ -175,7 +175,7 @@ grpc_error_handle grpc_deframe_unprocessed_incoming_frames(
          grpc_slice_buffer_remove_first(slices);
          continue;
        }
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_DATA_FH_4:
        s->stats.incoming.framing_bytes++;
        GPR_ASSERT(stream_out != nullptr);
--- a/src/core/ext/transport/chttp2/transport/frame_goaway.cc
+++ b/src/core/ext/transport/chttp2/transport/frame_goaway.cc
@ -70,7 +70,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->last_stream_id = (static_cast<uint32_t>(*cur)) << 24;
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_LSI1:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_LSI1;
@ -78,7 +78,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->last_stream_id |= (static_cast<uint32_t>(*cur)) << 16;
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_LSI2:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_LSI2;
@ -86,7 +86,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->last_stream_id |= (static_cast<uint32_t>(*cur)) << 8;
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_LSI3:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_LSI3;
@ -94,7 +94,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->last_stream_id |= (static_cast<uint32_t>(*cur));
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_ERR0:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_ERR0;
@ -102,7 +102,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->error_code = (static_cast<uint32_t>(*cur)) << 24;
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_ERR1:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_ERR1;
@ -110,7 +110,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->error_code |= (static_cast<uint32_t>(*cur)) << 16;
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_ERR2:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_ERR2;
@ -118,7 +118,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->error_code |= (static_cast<uint32_t>(*cur)) << 8;
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_ERR3:
      if (cur == end) {
        p->state = GRPC_CHTTP2_GOAWAY_ERR3;
@ -126,7 +126,7 @@ grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
      }
      p->error_code |= (static_cast<uint32_t>(*cur));
      ++cur;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_CHTTP2_GOAWAY_DEBUG:
      if (end != cur) {
        memcpy(p->debug_data + p->debug_pos, cur,
--- a/src/core/ext/transport/chttp2/transport/frame_settings.cc
+++ b/src/core/ext/transport/chttp2/transport/frame_settings.cc
@ -146,7 +146,7 @@ grpc_error_handle grpc_chttp2_settings_parser_parse(void* p,
        }
        parser->id = static_cast<uint16_t>((static_cast<uint16_t>(*cur)) << 8);
        cur++;
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_SPS_ID1:
        if (cur == end) {
          parser->state = GRPC_CHTTP2_SPS_ID1;
@ -154,7 +154,7 @@ grpc_error_handle grpc_chttp2_settings_parser_parse(void* p,
        }
        parser->id = static_cast<uint16_t>(parser->id | (*cur));
        cur++;
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_SPS_VAL0:
        if (cur == end) {
          parser->state = GRPC_CHTTP2_SPS_VAL0;
@ -162,7 +162,7 @@ grpc_error_handle grpc_chttp2_settings_parser_parse(void* p,
        }
        parser->value = (static_cast<uint32_t>(*cur)) << 24;
        cur++;
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_SPS_VAL1:
        if (cur == end) {
          parser->state = GRPC_CHTTP2_SPS_VAL1;
@ -170,7 +170,7 @@ grpc_error_handle grpc_chttp2_settings_parser_parse(void* p,
        }
        parser->value |= (static_cast<uint32_t>(*cur)) << 16;
        cur++;
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_SPS_VAL2:
        if (cur == end) {
          parser->state = GRPC_CHTTP2_SPS_VAL2;
@ -178,7 +178,7 @@ grpc_error_handle grpc_chttp2_settings_parser_parse(void* p,
        }
        parser->value |= (static_cast<uint32_t>(*cur)) << 8;
        cur++;
-      /* fallthrough */
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_SPS_VAL3:
        if (cur == end) {
          parser->state = GRPC_CHTTP2_SPS_VAL3;
--- a/src/core/ext/transport/chttp2/transport/hpack_parser.cc
+++ b/src/core/ext/transport/chttp2/transport/hpack_parser.cc
@ -603,6 +603,7 @@ grpc_error_handle HPackParser::parse_begin(const uint8_t* cur,
        // literal key
        return parse_lithdr_incidx_v(cur, end);
      }
+      ABSL_FALLTHROUGH_INTENDED;
    case 5:
    case 6:
      // inline encoded key index
@ -626,6 +627,7 @@ grpc_error_handle HPackParser::parse_begin(const uint8_t* cur,
        // illegal value.
        return parse_illegal_op(cur, end);
      }
+      ABSL_FALLTHROUGH_INTENDED;
    case 9:
    case 10:
    case 11:
@ -1209,8 +1211,8 @@ grpc_error_handle HPackParser::AppendString(const uint8_t* cur,
        return GRPC_ERROR_NONE;
      }
      GRPC_STATS_INC_HPACK_RECV_BINARY_BASE64();
-    /* fallthrough */
    b64_byte0:
+      ABSL_FALLTHROUGH_INTENDED;
    case BinaryState::kBase64Byte0:
      if (cur == end) {
        binary_ = BinaryState::kBase64Byte0;
@ -1226,8 +1228,8 @@ grpc_error_handle HPackParser::AppendString(const uint8_t* cur,
        goto b64_byte0;
      }
      base64_buffer_ = bits << 18;
-    /* fallthrough */
    b64_byte1:
+      ABSL_FALLTHROUGH_INTENDED;
    case BinaryState::kBase64Byte1:
      if (cur == end) {
        binary_ = BinaryState::kBase64Byte1;
@ -1243,8 +1245,8 @@ grpc_error_handle HPackParser::AppendString(const uint8_t* cur,
        goto b64_byte1;
      }
      base64_buffer_ |= bits << 12;
-    /* fallthrough */
    b64_byte2:
+      ABSL_FALLTHROUGH_INTENDED;
    case BinaryState::kBase64Byte2:
      if (cur == end) {
        binary_ = BinaryState::kBase64Byte2;
@ -1260,8 +1262,8 @@ grpc_error_handle HPackParser::AppendString(const uint8_t* cur,
        goto b64_byte2;
      }
      base64_buffer_ |= bits << 6;
-    /* fallthrough */
    b64_byte3:
+      ABSL_FALLTHROUGH_INTENDED;
    case BinaryState::kBase64Byte3:
      if (cur == end) {
        binary_ = BinaryState::kBase64Byte3;
--- a/src/core/ext/transport/chttp2/transport/parsing.cc
+++ b/src/core/ext/transport/chttp2/transport/parsing.cc
@ -109,8 +109,8 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
      if (cur == end) {
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
    dts_fh_0:
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_0:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_frame_size = (static_cast<uint32_t>(*cur)) << 16;
@ -118,7 +118,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_1;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_1:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_frame_size |= (static_cast<uint32_t>(*cur)) << 8;
@ -126,7 +126,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_2;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_2:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_frame_size |= *cur;
@ -134,7 +134,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_3;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_3:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_frame_type = *cur;
@ -142,7 +142,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_4;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_4:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_frame_flags = *cur;
@ -150,7 +150,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_5;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_5:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_stream_id = ((static_cast<uint32_t>(*cur)) & 0x7f) << 24;
@ -158,7 +158,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_6;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_6:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_stream_id |= (static_cast<uint32_t>(*cur)) << 16;
@ -166,7 +166,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_7;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_7:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_stream_id |= (static_cast<uint32_t>(*cur)) << 8;
@ -174,7 +174,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
        t->deframe_state = GRPC_DTS_FH_8;
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FH_8:
      GPR_DEBUG_ASSERT(cur < end);
      t->incoming_stream_id |= (static_cast<uint32_t>(*cur));
@ -208,7 +208,7 @@ grpc_error_handle grpc_chttp2_perform_read(grpc_chttp2_transport* t,
      if (++cur == end) {
        return GRPC_ERROR_NONE;
      }
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case GRPC_DTS_FRAME:
      GPR_DEBUG_ASSERT(cur < end);
      if (static_cast<uint32_t>(end - cur) == t->incoming_frame_size) {
--- a/src/core/ext/transport/chttp2/transport/varint.cc
+++ b/src/core/ext/transport/chttp2/transport/varint.cc
@ -20,6 +20,8 @@

 #include "src/core/ext/transport/chttp2/transport/varint.h"

+#include "absl/base/attributes.h"
+
 uint32_t grpc_chttp2_hpack_varint_length(uint32_t tail_value) {
  if (tail_value < (1 << 7)) {
    return 2;
@ -39,16 +41,16 @@ void grpc_chttp2_hpack_write_varint_tail(uint32_t tail_value, uint8_t* target,
  switch (tail_length) {
    case 5:
      target[4] = static_cast<uint8_t>((tail_value >> 28) | 0x80);
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case 4:
      target[3] = static_cast<uint8_t>((tail_value >> 21) | 0x80);
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case 3:
      target[2] = static_cast<uint8_t>((tail_value >> 14) | 0x80);
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case 2:
      target[1] = static_cast<uint8_t>((tail_value >> 7) | 0x80);
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case 1:
      target[0] = static_cast<uint8_t>((tail_value) | 0x80);
  }
--- a/src/core/lib/gpr/murmur_hash.cc
+++ b/src/core/lib/gpr/murmur_hash.cc
@ -22,6 +22,8 @@

 #include <string.h>

+#include "absl/base/attributes.h"
+
 #define ROTL32(x, r) (((x) << (r)) | ((x) >> (32 - (r))))

 #define FMIX32(h)    \
@ -61,10 +63,10 @@ uint32_t gpr_murmur_hash3(const void* key, size_t len, uint32_t seed) {
  switch (len & 3) {
    case 3:
      k1 ^= (static_cast<uint32_t>(keyptr[2])) << 16;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case 2:
      k1 ^= (static_cast<uint32_t>(keyptr[1])) << 8;
-    /* fallthrough */
+      ABSL_FALLTHROUGH_INTENDED;
    case 1:
      k1 ^= keyptr[0];
      k1 *= c1;
--- a/src/core/lib/iomgr/timer_manager.cc
+++ b/src/core/lib/iomgr/timer_manager.cc
@ -250,7 +250,7 @@ static void timer_main_loop() {
          gpr_log(GPR_INFO, "timers not checked: expect another thread to");
        }
        next = GRPC_MILLIS_INF_FUTURE;
-      // fallthrough
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_TIMERS_CHECKED_AND_EMPTY:
        if (!wait_until(next)) {
          return;
--- a/src/core/lib/json/json_reader.cc
+++ b/src/core/lib/json/json_reader.cc
@ -347,8 +347,7 @@ JsonReader::Status JsonReader::Run() {
            }
            if (!SetNumber()) return Status::GRPC_JSON_PARSE_ERROR;
            state_ = State::GRPC_JSON_STATE_VALUE_END;
-            /* The missing break here is intentional. */
-            /* fallthrough */
+            ABSL_FALLTHROUGH_INTENDED;

          case State::GRPC_JSON_STATE_VALUE_END:
          case State::GRPC_JSON_STATE_OBJECT_KEY_BEGIN:
--- a/src/core/lib/slice/slice_internal.h
+++ b/src/core/lib/slice/slice_internal.h
@ -231,6 +231,7 @@ inline int grpc_slice_refcount::Eq(const grpc_slice& a, const grpc_slice& b) {
      GPR_DEBUG_ASSERT(
          (GRPC_STATIC_METADATA_INDEX(a) == GRPC_STATIC_METADATA_INDEX(b)) ==
          (a.refcount == b.refcount));
+      ABSL_FALLTHROUGH_INTENDED;
    case Type::INTERNED:
      return a.refcount == b.refcount;
    case Type::NOP:
--- a/test/core/iomgr/tcp_client_posix_test.cc
+++ b/test/core/iomgr/tcp_client_posix_test.cc
@ -170,7 +170,7 @@ void test_fails(void) {
        break;
      case GRPC_TIMERS_NOT_CHECKED:
        polling_deadline = 0;
-      // fallthrough
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_TIMERS_CHECKED_AND_EMPTY:
        GPR_ASSERT(GRPC_LOG_IF_ERROR(
            "pollset_work",
--- a/test/core/iomgr/tcp_client_uv_test.cc
+++ b/test/core/iomgr/tcp_client_uv_test.cc
@ -166,7 +166,7 @@ void test_fails(void) {
        break;
      case GRPC_TIMERS_NOT_CHECKED:
        polling_deadline = grpc_timespec_to_millis_round_up(now);
-      // fallthrough
+        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_TIMERS_CHECKED_AND_EMPTY:
        GPR_ASSERT(GRPC_LOG_IF_ERROR(
            "pollset_work",