[-Wunsafe-buffer-usage] Fix a fallthrough case in UPCStandalonePointer getFixits

[ziqingluo-90]

LGTM!

[NoQ]

clang/lib/Analysis/UnsafeBufferUsage.cpp

1512

This one's probably also incorrect, just harder to reach.

[NoQ]

Aha great LGTM!

You can also remove both [[fallthrough]]; annotations now that there's an unconditional break in front of them.

clang/lib/Analysis/UnsafeBufferUsage.cpp

case Strategy::Kind::Span: {
     std::optional<SourceLocation> EndOfOperand =
         getEndCharLoc(BaseDeclRefExpr, SM, Ctx.getLangOpts());
     if (EndOfOperand) {
       return FixItList{{FixItHint::CreateRemoval(derefRange),
                         FixItHint::CreateInsertion(
                             (*EndOfOperand).getLocWithOffset(1), "[0]")}};
     }
   }
     [[fallthrough]];
   case Strategy::Kind::Iterator:
   case Strategy::Kind::Array:
   case Strategy::Kind::Vector:
     llvm_unreachable("Strategy not implemented yet!");
   case Strategy::Kind::Wontfix:
     llvm_unreachable("Invalid strategy!");
   }
 
case Strategy::Kind::Span: {
       SourceManager &SM = Ctx.getSourceManager();
       // Inserts the .data() after the DRE
       std::optional<SourceLocation> EndOfOperand =
           getPastLoc(Node, SM, Ctx.getLangOpts());
 
       if (EndOfOperand)
         return FixItList{{FixItHint::CreateInsertion(
             *EndOfOperand, ".data()")}};
+      // FIXME: Points inside a macro expansion.
+      break;
     }
       [[fallthrough]];
     case Strategy::Kind::Wontfix:
     case Strategy::Kind::Iterator:
     case Strategy::Kind::Array:
     case Strategy::Kind::Vector:
       llvm_unreachable("unsupported strategies for FixableGadgets");
   }

clang/test/SemaCXX/warn-unsafe-buffer-usage-test-unreachable.cpp

+// RUN: %clang_cc1 -std=c++20 -Wunsafe-buffer-usage -fsafe-buffer-usage-suggestions -verify %s
+
+// expected-no-diagnostics
+
+typedef unsigned __darwin_size_t;
+typedef __darwin_size_t size_t;
+ #define bzero(s, n) __builtin_bzero(s, n)
+void __nosan_bzero(void *dst, size_t sz) { bzero(dst, sz); }