Only warn at self-initialization if some later use is always uninitialized.

llvm-svn: 142538

clang/lib/Sema/AnalysisBasedWarnings.cpp

@@ -586,9 +586,10 @@ public:
       // 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)
+      if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
         DiagnoseUninitializedUse(S, vd, vd->getInit()->IgnoreParenCasts(),
-                                 true, /* alwaysReportSelfInit */ true);
+                                 /* isAlwaysUninit */ true,
+                                 /* alwaysReportSelfInit */ true);
       else {
         // Sort the uses by their SourceLocations.  While not strictly
         // guaranteed to produce them in line/column order, this will provide
@@ -610,6 +611,16 @@ public:
     }
     delete uses;
   }
+
+private:
+  static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
+  for (UsesVec::const_iterator i = vec->begin(), e = vec->end(); i != e; ++i) {
+    if (i->second) {
+      return true;
+    }
+  }
+  return false;
+}
 };
 }
 

clang/test/Sema/uninit-variables.c

@@ -44,6 +44,15 @@ int test7(int y) {
   return x; // expected-warning{{variable 'x' may be uninitialized when used here}}
 }
 
+int test7b(int y) {
+  int x = x; // expected-note{{variable 'x' is declared here}}
+  if (y)
+    x = 1;
+  // Warn with "may be uninitialized" here (not "is uninitialized"), since the
+  // self-initialization is intended to suppress a -Wuninitialized warning.
+  return x; // expected-warning{{variable 'x' may be uninitialized when used here}}
+}
+
 int test8(int y) {
   int x;
   if (y)
@@ -415,4 +424,3 @@ void rdar9432305(float *P) {
   for (; i < 10000; ++i) // expected-warning {{variable 'i' is uninitialized when used here}}
     P[i] = 0.0f;
 }
-