[ReachableCode] Skip over ExprWithCleanups in isConfigurationValue

[timshen]

Summary

Fixes pr29152.

[pirama]

Tim: Thanks for looking into this. It's definitely a simpler fix than I thought it would be :)

[pirama]

Ping... I am not the author of this patch, but am interested in seeing the issue fixed :)

[srhines]

This looks good to me, but I would prefer if one of the more experienced Clang folks could officially LGTM this. Thanks.

[timshen]

Simplified the test.

[srhines]

Ping. Other developers (Firefox) are now starting to hit this issue.

[krememek]

LGTM.

clang/include/clang/AST/Stmt.h

public:
 
   /// viewAST - Visualize an AST rooted at this Stmt* using GraphViz.  Only
   ///   works on systems with GraphViz (Mac OS X) or dot+gv installed.
   void viewAST() const;
 
   /// Skip past any implicit AST nodes which might surround this
   /// statement, such as ExprWithCleanups or ImplicitCastExpr nodes.
   Stmt *IgnoreImplicit();
+  const Stmt *IgnoreImplicit() const {
+    return const_cast<Stmt *>(this)->IgnoreImplicit();
+  }
 
   /// \brief Skip no-op (attributed, compound) container stmts and skip captured
   /// stmt at the top, if \a IgnoreCaptured is true.
   Stmt *IgnoreContainers(bool IgnoreCaptured = false);
 
   const Stmt *stripLabelLikeStatements() const;
   Stmt *stripLabelLikeStatements() {
     return const_cast<Stmt*>(

clang/lib/Analysis/ReachableCode.cpp

 static bool isConfigurationValue(const Stmt *S,
                                  Preprocessor &PP,
                                  SourceRange *SilenceableCondVal = nullptr,
                                  bool IncludeIntegers = true,
                                  bool WrappedInParens = false) {
   if (!S)
     return false;
 
+  S = S->IgnoreImplicit();
+
   if (const Expr *Ex = dyn_cast<Expr>(S))
     S = Ex->IgnoreCasts();
 
   // Special case looking for the sigil '()' around an integer literal.
   if (const ParenExpr *PE = dyn_cast<ParenExpr>(S))
     if (!PE->getLocStart().isMacroID())
       return isConfigurationValue(PE->getSubExpr(), PP, SilenceableCondVal, 
                                   IncludeIntegers, true);

clang/test/SemaCXX/PR29152.cpp

+// RUN: %clang_cc1 -fsyntax-only -Wunreachable-code -verify %s
+
+static const bool False = false;
+
+struct A {
+  ~A();
+  operator bool();
+};
+void Bar();
+
+void Foo() {
+  if (False && A()) {
+    Bar(); // expected-no-diagnostics
+  }
+}