-Wunreachable-code: treat 'const bool' locals as control values.

llvm-svn: 204001

clang/lib/Analysis/ReachableCode.cpp

@@ -236,7 +236,12 @@ static bool isConfigurationValue(const Stmt *S,
         // We could generalize this to local variables, but it isn't
         // clear if those truly represent configuration values that
         // gate unreachable code.
-        return !VD->hasLocalStorage();
+        if (!VD->hasLocalStorage())
+          return true;
+
+        // As a heuristic, locals that have been marked 'const' explicitly
+        // can be treated as configuration values as well.
+        return VD->getType().isLocalConstQualified();
       }
       return false;
     }

clang/test/SemaCXX/warn-unreachable.cpp

@@ -199,3 +199,22 @@ int test_arithmetic() {
   return 2; // expected-warning {{never be executed}}
 }
 
+int test_treat_const_bool_local_as_config_value() {
+  const bool controlValue = false;
+  if (!controlValue)
+    return 1;
+  test_treat_const_bool_local_as_config_value(); // no-warning
+  return 0;
+}
+
+int test_treat_non_const_bool_local_as_non_config_value() {
+  bool controlValue = false;
+  if (!controlValue)
+    return 1;
+  // There is no warning here because 'controlValue' isn't really
+  // a control value at all.  The CFG will not treat this
+  // branch as unreachable.
+  test_treat_non_const_bool_local_as_non_config_value(); // no-warning
+  return 0;
+}
+