[clang-tidy][NFC] Fix clang-analyzer-optin.cplusplus.UninitializedObj…

…ect findings

Fix issues found by clang-tidy in clang-tidy source directory.

clang-tools-extra/clang-tidy/modernize/PassByValueCheck.cpp

@@ -75,9 +75,9 @@ static bool paramReferredExactlyOnce(const CXXConstructorDecl *Ctor,
     /// the
     /// given constructor.
     bool hasExactlyOneUsageIn(const CXXConstructorDecl *Ctor) {
-      Count = 0;
+      Count = 0U;
       TraverseDecl(const_cast<CXXConstructorDecl *>(Ctor));
-      return Count == 1;
+      return Count == 1U;
     }
 
   private:
@@ -88,7 +88,7 @@ static bool paramReferredExactlyOnce(const CXXConstructorDecl *Ctor,
       if (const ParmVarDecl *To = dyn_cast<ParmVarDecl>(D->getDecl())) {
         if (To == ParamDecl) {
           ++Count;
-          if (Count > 1) {
+          if (Count > 1U) {
             // No need to look further, used more than once.
             return false;
           }
@@ -98,7 +98,7 @@ static bool paramReferredExactlyOnce(const CXXConstructorDecl *Ctor,
     }
 
     const ParmVarDecl *ParamDecl;
-    unsigned Count;
+    unsigned Count = 0U;
   };
 
   return ExactlyOneUsageVisitor(ParamDecl).hasExactlyOneUsageIn(Ctor);