Avoid multiple -Wunreachable-code diagnostics that are triggered by

the same source range and use the unary operator fixit only when it
actually silences the warning.

rdar://24570531

Differential Revision: https://reviews.llvm.org/D28231

llvm-svn: 291757

2 files changed, 25 insertions, 5 deletions

diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
index 69d000c03ba..a2f3203762f 100644
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -218,11 +218,21 @@ static bool isConfigurationValue(const Stmt *S,
     }
     case Stmt::UnaryOperatorClass: {
       const UnaryOperator *UO = cast<UnaryOperator>(S);
-      if (SilenceableCondVal) 
-        *SilenceableCondVal = UO->getSourceRange();      
-      return UO->getOpcode() == UO_LNot &&
-             isConfigurationValue(UO->getSubExpr(), PP, SilenceableCondVal,
-                                  IncludeIntegers, WrappedInParens);
+      if (UO->getOpcode() != UO_LNot)
+        return false;
+      bool SilenceableCondValNotSet =
+          SilenceableCondVal && SilenceableCondVal->getBegin().isInvalid();
+      bool IsSubExprConfigValue =
+          isConfigurationValue(UO->getSubExpr(), PP, SilenceableCondVal,
+                               IncludeIntegers, WrappedInParens);
+      // Update the silenceable condition value source range only if the range
+      // was set directly by the child expression.
+      if (SilenceableCondValNotSet &&
+          SilenceableCondVal->getBegin().isValid() &&
+          *SilenceableCondVal ==
+              UO->getSubExpr()->IgnoreCasts()->getSourceRange())
+        *SilenceableCondVal = UO->getSourceRange();
+      return IsSubExprConfigValue;
     }
     default:
       return false;
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 5953d020b4f..a987a8ce0b3 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -56,6 +56,8 @@ using namespace clang;
 namespace {
   class UnreachableCodeHandler : public reachable_code::Callback {
     Sema &S;
+    SourceRange PreviousSilenceableCondVal;
+
   public:
     UnreachableCodeHandler(Sema &s) : S(s) {}
 
@@ -64,6 +66,14 @@ namespace {
                            SourceRange SilenceableCondVal,
                            SourceRange R1,
                            SourceRange R2) override {
+      // Avoid reporting multiple unreachable code diagnostics that are
+      // triggered by the same conditional value.
+      if (PreviousSilenceableCondVal.isValid() &&
+          SilenceableCondVal.isValid() &&
+          PreviousSilenceableCondVal == SilenceableCondVal)
+        return;
+      PreviousSilenceableCondVal = SilenceableCondVal;
+
       unsigned diag = diag::warn_unreachable;
       switch (UK) {
         case reachable_code::UK_Break: