Use C++17's [[fallthrough]]. NFC (#2091)

5 files changed, 20 insertions, 17 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 48812d13..2bfe62a8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -164,7 +164,7 @@ else ()
   #   interfaces, etc.
   # disable -Wpointer-arith: this is a GCC extension, and doesn't work in MSVC.
   add_definitions(
-    -Wall -Wextra -Wno-unused-parameter -Wpointer-arith -Wuninitialized
+    -Wall -Wextra -Wno-unused-parameter -Wpointer-arith -Wuninitialized -Wimplicit-fallthrough
   )
 
   set(CMAKE_CXX_EXTENSIONS OFF)
@@ -563,7 +563,9 @@ if (BUILD_TOOLS)
 
     if (COMPILER_IS_GNU)
       target_compile_options(uv_a PRIVATE "-Wno-sign-compare")
-    endif ()
+    elseif (COMPILER_IS_CLANG)
+      target_compile_options(uv_a PRIVATE "-Wno-implicit-fallthrough")
+    endif()
   endif()
 
   # wasm-interp
diff --git a/src/binary-reader-objdump.cc b/src/binary-reader-objdump.cc
index 23f2016f..905647f4 100644
--- a/src/binary-reader-objdump.cc
+++ b/src/binary-reader-objdump.cc
@@ -691,6 +691,7 @@ void BinaryReaderObjdumpDisassemble::LogOpcode(const char* fmt, ...) {
         case Opcode::Catch:
         case Opcode::CatchAll:
           indent_level--;
+          break;
         default:
           break;
       }
diff --git a/src/binary-reader.cc b/src/binary-reader.cc
index 0c399461..0e0b894a 100644
--- a/src/binary-reader.cc
+++ b/src/binary-reader.cc
@@ -1719,7 +1719,7 @@ Result BinaryReader::ReadInstructions(bool stop_on_end,
       case Opcode::DataDrop:
         ERROR_IF(data_count_ == kInvalidIndex,
                  "data.drop requires data count section");
-        // Fallthrough.
+        [[fallthrough]];
       case Opcode::ElemDrop: {
         Index segment;
         CHECK_RESULT(ReadIndex(&segment, "segment index"));
diff --git a/src/error-formatter.cc b/src/error-formatter.cc
index 5b0d4952..9a14cfac 100644
--- a/src/error-formatter.cc
+++ b/src/error-formatter.cc
@@ -94,7 +94,7 @@ std::string FormatErrorsToString(const Errors& errors,
           break;
         case PrintHeader::Once:
           print_header = PrintHeader::Never;
-          // Fallthrough.
+          [[fallthrough]];
         case PrintHeader::Always:
           result += header;
           result += ":\n";
diff --git a/src/prebuilt/lexer-keywords.cc b/src/prebuilt/lexer-keywords.cc
index bb7152fc..4a7da0e0 100644
--- a/src/prebuilt/lexer-keywords.cc
+++ b/src/prebuilt/lexer-keywords.cc
@@ -96,55 +96,55 @@ Perfect_Hash::hash (const char *str, size_t len)
     {
       default:
         hval += asso_values[static_cast<unsigned char>(str[26])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 26:
       case 25:
       case 24:
       case 23:
         hval += asso_values[static_cast<unsigned char>(str[22])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 22:
       case 21:
       case 20:
       case 19:
         hval += asso_values[static_cast<unsigned char>(str[18])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 18:
         hval += asso_values[static_cast<unsigned char>(str[17])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 17:
         hval += asso_values[static_cast<unsigned char>(str[16])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 16:
       case 15:
         hval += asso_values[static_cast<unsigned char>(str[14])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 14:
       case 13:
       case 12:
         hval += asso_values[static_cast<unsigned char>(str[11])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 11:
       case 10:
         hval += asso_values[static_cast<unsigned char>(str[9])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 9:
       case 8:
         hval += asso_values[static_cast<unsigned char>(str[7])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 7:
         hval += asso_values[static_cast<unsigned char>(str[6])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 6:
         hval += asso_values[static_cast<unsigned char>(str[5])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 5:
         hval += asso_values[static_cast<unsigned char>(str[4])];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 4:
       case 3:
         hval += asso_values[static_cast<unsigned char>(str[2]+1)];
-      /*FALLTHROUGH*/
+        [[fallthrough]];
       case 2:
       case 1:
         hval += asso_values[static_cast<unsigned char>(str[0]+1)];