Tweak -Wuninitialized's handling of 'int x = x' to report that as the root cause of an uninitialized variable IFF there are other uses of that uninitialized variable. Fixes <rdar://problem/9259237>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@141881 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 46 insertions, 24 deletions

diff --git a/lib/Sema/AnalysisBasedWarnings.cpp b/lib/Sema/AnalysisBasedWarnings.cpp
index f461772ba7..babb8af18b 100644
--- a/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/lib/Sema/AnalysisBasedWarnings.cpp
@@ -470,7 +470,8 @@ static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
 /// as a warning. If a pariticular use is one we omit warnings for, returns
 /// false.
 static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
-                                     const Expr *E, bool isAlwaysUninit) {
+                                     const Expr *E, bool isAlwaysUninit,
+                                     bool alwaysReportSelfInit = false) {
   bool isSelfInit = false;
 
   if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
@@ -490,7 +491,7 @@ static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
       // TODO: Should we suppress maybe-uninitialized warnings for
       // variables initialized in this way?
       if (const Expr *Initializer = VD->getInit()) {
-        if (DRE == Initializer->IgnoreParenImpCasts())
+        if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
           return false;
 
         ContainsReference CR(S.Context, DRE);
@@ -541,7 +542,7 @@ struct SLocSort {
 class UninitValsDiagReporter : public UninitVariablesHandler {
   Sema &S;
   typedef SmallVector<UninitUse, 2> UsesVec;
-  typedef llvm::DenseMap<const VarDecl *, UsesVec*> UsesMap;
+  typedef llvm::DenseMap<const VarDecl *, std::pair<UsesVec*, bool> > UsesMap;
   UsesMap *uses;
   
 public:
@@ -549,17 +550,26 @@ public:
   ~UninitValsDiagReporter() { 
     flushDiagnostics();
   }
-  
-  void handleUseOfUninitVariable(const Expr *ex, const VarDecl *vd,
-                                 bool isAlwaysUninit) {
+
+  std::pair<UsesVec*, bool> &getUses(const VarDecl *vd) {
     if (!uses)
       uses = new UsesMap();
-    
-    UsesVec *&vec = (*uses)[vd];
+
+    UsesMap::mapped_type &V = (*uses)[vd];
+    UsesVec *&vec = V.first;
     if (!vec)
       vec = new UsesVec();
     
-    vec->push_back(std::make_pair(ex, isAlwaysUninit));
+    return V;
+  }
+  
+  void handleUseOfUninitVariable(const Expr *ex, const VarDecl *vd,
+                                 bool isAlwaysUninit) {
+    getUses(vd).first->push_back(std::make_pair(ex, isAlwaysUninit));
+  }
+  
+  void handleSelfInit(const VarDecl *vd) {
+    getUses(vd).second = true;    
   }
   
   void flushDiagnostics() {
@@ -568,22 +578,34 @@ public:
     
     for (UsesMap::iterator i = uses->begin(), e = uses->end(); i != e; ++i) {
       const VarDecl *vd = i->first;
-      UsesVec *vec = i->second;
-
-      // Sort the uses by their SourceLocations.  While not strictly
-      // guaranteed to produce them in line/column order, this will provide
-      // a stable ordering.
-      std::sort(vec->begin(), vec->end(), SLocSort());
-      
-      for (UsesVec::iterator vi = vec->begin(), ve = vec->end(); vi != ve;
-           ++vi) {
-        if (DiagnoseUninitializedUse(S, vd, vi->first,
-                                      /*isAlwaysUninit=*/vi->second))
-          // Skip further diagnostics for this variable. We try to warn only on
-          // the first point at which a variable is used uninitialized.
-          break;
+      const UsesMap::mapped_type &V = i->second;
+
+      UsesVec *vec = V.first;
+      bool hasSelfInit = V.second;
+
+      // Specially handle the case where we have uses of an uninitialized 
+      // variable, but the root cause is an idiomatic self-init.  We want
+      // to report the diagnostic at the self-init since that is the root cause.
+      if (!vec->empty() && hasSelfInit)
+        DiagnoseUninitializedUse(S, vd, vd->getInit()->IgnoreParenCasts(),
+                                 true, /* alwaysReportSelfInit */ true);
+      else {
+        // Sort the uses by their SourceLocations.  While not strictly
+        // guaranteed to produce them in line/column order, this will provide
+        // a stable ordering.
+        std::sort(vec->begin(), vec->end(), SLocSort());
+        
+        for (UsesVec::iterator vi = vec->begin(), ve = vec->end(); vi != ve;
+             ++vi) {
+          if (DiagnoseUninitializedUse(S, vd, vi->first,
+                                        /*isAlwaysUninit=*/vi->second))
+            // Skip further diagnostics for this variable. We try to warn only
+            // on the first point at which a variable is used uninitialized.
+            break;
+        }
       }
-
+      
+      // Release the uses vector.
       delete vec;
     }
     delete uses;