[clang] Add unreachable after fully covered switches, avoid GCC warnings. NFC.

[mstorsjo]

This avoids the following warnings:

../../clang/lib/AST/ExprConstant.cpp: In member function ‘bool {anonymous}::IntExprEvaluator::VisitBuiltinCallExpr(const clang::CallExpr*, unsigned int)’:
../../clang/lib/AST/ExprConstant.cpp:14104:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
14104 |   }
      |   ^
../../clang/lib/AST/ExprConstant.cpp:14105:3: note: here
14105 |   case Builtin::BIstrlen:
      |   ^~~~
../../clang/lib/Driver/ToolChains/CommonArgs.cpp: In function ‘std::string clang::driver::tools::complexRangeKindToStr(clang::LangOptionsBase::ComplexRangeKind ’:
../../clang/lib/Driver/ToolChains/CommonArgs.cpp:3523:1: warning: control reaches end of non-void function [-Wreturn-type]
 3523 | }
      | ^

[llvmbot]

@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: Martin Storsjö (mstorsjo)

Changes

This avoids the following warnings:

../../clang/lib/AST/ExprConstant.cpp: In member function ‘bool {anonymous}::IntExprEvaluator::VisitBuiltinCallExpr(const clang::CallExpr*, unsigned int)’:
../../clang/lib/AST/ExprConstant.cpp:14104:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
14104 |   }
      |   ^
../../clang/lib/AST/ExprConstant.cpp:14105:3: note: here
14105 |   case Builtin::BIstrlen:
      |   ^~~~
../../clang/lib/Driver/ToolChains/CommonArgs.cpp: In function ‘std::string clang::driver::tools::complexRangeKindToStr(clang::LangOptionsBase::ComplexRangeKind ’:
../../clang/lib/Driver/ToolChains/CommonArgs.cpp:3523:1: warning: control reaches end of non-void function [-Wreturn-type]
 3523 | }
      | ^

---

Full diff: https://github.com/llvm/llvm-project/pull/159330.diff

2 Files Affected:

• (modified) clang/lib/AST/ExprConstant.cpp (+1)
• (modified) clang/lib/Driver/ToolChains/CommonArgs.cpp (+1)

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 12e4e25bd29c4..15c4a323b7d6a 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -14101,6 +14101,7 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
       return Success(Result, E);
     }
     }
+    llvm_unreachable("Fully covered switch above");
   }
   case Builtin::BIstrlen:
   case Builtin::BIwcslen:
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index b50549219e4e8..08cd98fd04df0 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -3520,6 +3520,7 @@ std::string tools::complexRangeKindToStr(LangOptions::ComplexRangeKind Range) {
     return "none";
     break;
   }
+  llvm_unreachable("Fully covered switch above");
 }
 
 std::string

[cor3ntin]

I'm not opposed to this change but we might want to report that to GCC, it is a false positive

[mstorsjo]

I'm not opposed to this change but we might want to report that to GCC, it is a false positive

GCC considers that enums potentially can have any representable value - this is a known longtime difference between GCC and Clang to the point that we have it mentioned in our CodingStandards.