[PATCH] D107933: [clang] Expose unreachable fallthrough annotation warning

[Nathan Chancellor via Phabricator via cfe-commits]

nathanchance updated this revision to Diff 366363.
nathanchance added a comment.

- -Wimplicit-fallthrough-unreachable -> -Wunreachable-code-fallthrough, enabled under -Wunreachable-code (Dávid, Aaron).

- Drop "case 225" from new test, as it does not add to test coverage (Nick).

- Add -Wunreachable-code-fallthrough to PR30636 test command, as it is explicitly testing that there is no unreachable warning with template function instantiation.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107933/new/

https://reviews.llvm.org/D107933

Files:
  clang/include/clang/Basic/DiagnosticGroups.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/AnalysisBasedWarnings.cpp
  clang/test/SemaCXX/P30636.cpp
  clang/test/SemaCXX/switch-implicit-fallthrough.cpp


Index: clang/test/SemaCXX/switch-implicit-fallthrough.cpp
===================================================================
--- clang/test/SemaCXX/switch-implicit-fallthrough.cpp
+++ clang/test/SemaCXX/switch-implicit-fallthrough.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough -Wunreachable-code-fallthrough %s
 
 
 int fallthrough(int n) {
@@ -193,6 +193,26 @@
         ;
   }
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunreachable-code-fallthrough"
+  switch (n) {
+      n += 300;
+      [[clang::fallthrough]];  // no warning here
+    case 221:
+      return 1;
+      [[clang::fallthrough]];  // no warning here
+    case 222:
+      return 2;
+      __attribute__((fallthrough)); // no warning here
+    case 223:
+      if (1)
+        return 3;
+      __attribute__((fallthrough)); // no warning here
+    case 224:
+      n += 400;
+  }
+#pragma clang diagnostic pop
+
   long p = static_cast<long>(n) * n;
   switch (sizeof(p)) {
     case 9:
Index: clang/test/SemaCXX/P30636.cpp
===================================================================
--- clang/test/SemaCXX/P30636.cpp
+++ clang/test/SemaCXX/P30636.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough -Wunreachable-code-fallthrough %s
 // expected-no-diagnostics
 
 template<bool param>
Index: clang/lib/Sema/AnalysisBasedWarnings.cpp
===================================================================
--- clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -1125,7 +1125,7 @@
                 // unreachable in all instantiations of the template.
                 if (!IsTemplateInstantiation)
                   S.Diag(AS->getBeginLoc(),
-                         diag::warn_fallthrough_attr_unreachable);
+                         diag::warn_unreachable_fallthrough_attr);
                 markFallthroughVisited(AS);
                 ++AnnotatedCnt;
                 break;
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -682,6 +682,9 @@
 def warn_unreachable_loop_increment : Warning<
   "loop will run at most once (loop increment never executed)">,
   InGroup<UnreachableCodeLoopIncrement>, DefaultIgnore;
+def warn_unreachable_fallthrough_attr : Warning<
+  "fallthrough annotation in unreachable code">,
+  InGroup<UnreachableCodeFallthrough>, DefaultIgnore;
 def note_unreachable_silence : Note<
   "silence by adding parentheses to mark code as explicitly dead">;
 
@@ -9578,9 +9581,6 @@
   "fallthrough annotation is outside switch statement">;
 def err_fallthrough_attr_invalid_placement : Error<
   "fallthrough annotation does not directly precede switch label">;
-def warn_fallthrough_attr_unreachable : Warning<
-  "fallthrough annotation in unreachable code">,
-  InGroup<ImplicitFallthrough>, DefaultIgnore;
 
 def warn_unreachable_default : Warning<
   "default label in switch which covers all enumeration values">,
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -819,8 +819,10 @@
 //  under separate flags.
 //
 def UnreachableCodeLoopIncrement : DiagGroup<"unreachable-code-loop-increment">;
+def UnreachableCodeFallthrough : DiagGroup<"unreachable-code-fallthrough">;
 def UnreachableCode : DiagGroup<"unreachable-code",
-                                [UnreachableCodeLoopIncrement]>;
+                                [UnreachableCodeLoopIncrement,
+                                 UnreachableCodeFallthrough]>;
 def UnreachableCodeBreak : DiagGroup<"unreachable-code-break">;
 def UnreachableCodeReturn : DiagGroup<"unreachable-code-return">;
 def UnreachableCodeAggressive : DiagGroup<"unreachable-code-aggressive",


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D107933.366363.patch
Type: text/x-patch
Size: 4200 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20210813/6baabc87/attachment-0001.bin>