[clang-tidy][NFC] Fix cppcoreguidelines-init-variables findings

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

Author: PiotrZSL

clang-tools-extra/clang-tidy/ClangTidy.cpp

@@ -133,7 +133,7 @@ class ErrorReporter {
       for (const FileByteRange &FBR : Error.Message.Ranges)
         Diag << getRange(FBR);
       // FIXME: explore options to support interactive fix selection.
-      const llvm::StringMap<Replacements> *ChosenFix;
+      const llvm::StringMap<Replacements> *ChosenFix = nullptr;
       if (ApplyFixes != FB_NoFix &&
           (ChosenFix = getFixIt(Error, ApplyFixes == FB_FixNotes))) {
         for (const auto &FileAndReplacements : *ChosenFix) {

clang-tools-extra/clang-tidy/ClangTidyCheck.cpp

@@ -97,7 +97,7 @@ static std::optional<bool> getAsBool(StringRef Value,
     return Parsed;
   // To maintain backwards compatability, we support parsing numbers as
   // booleans, even though its not supported in YAML.
-  long long Number;
+  long long Number = 0;
   if (!Value.getAsInteger(10, Number))
     return Number != 0;
   return std::nullopt;

clang-tools-extra/clang-tidy/abseil/DurationFactoryScaleCheck.cpp

@@ -159,7 +159,7 @@ void DurationFactoryScaleCheck::check(const MatchFinder::MatchResult &Result) {
     return;
 
   DurationScale Scale = *MaybeScale;
-  const Expr *Remainder;
+  const Expr *Remainder = nullptr;
   std::optional<DurationScale> NewScale;
 
   // We next handle the cases of multiplication and division.

clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp

@@ -103,9 +103,9 @@ StrCatCheckResult processCall(const CallExpr *RootCall, bool IsAppend,
 }  // namespace
 
 void RedundantStrcatCallsCheck::check(const MatchFinder::MatchResult& Result) {
-  bool IsAppend;
+  bool IsAppend = false;
 
-  const CallExpr* RootCall;
+  const CallExpr *RootCall = nullptr;
   if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrCat"))) 
   	IsAppend = false;
   else if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrAppend"))) 

clang-tools-extra/clang-tidy/altera/UnrollLoopsCheck.cpp

@@ -203,7 +203,7 @@ bool UnrollLoopsCheck::hasLargeNumIterations(const Stmt *Statement,
   // If increment is binary and not one of +, -, *, /, we can't know the loop
   // bounds.
   if (const auto *Op = dyn_cast<BinaryOperator>(Increment)) {
-    int ConstantValue;
+    int ConstantValue = 0;
     if (!extractValue(ConstantValue, Op, Context))
       return true;
     switch (Op->getOpcode()) {

clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp

@@ -151,7 +151,7 @@ void ImplicitWideningOfMultiplicationResultCheck::handlePointerOffsetting(
 
   // We are looking for a pointer offset operation,
   // with one hand being a pointer, and another one being an offset.
-  const Expr *PointerExpr, *IndexExpr;
+  const Expr *PointerExpr = nullptr, *IndexExpr = nullptr;
   if (const auto *BO = dyn_cast<BinaryOperator>(E)) {
     PointerExpr = BO->getLHS();
     IndexExpr = BO->getRHS();

clang-tools-extra/clang-tidy/bugprone/MisplacedWideningCastCheck.cpp

@@ -163,7 +163,7 @@ static int relativeCharSizesW(BuiltinType::Kind Kind) {
 }
 
 static bool isFirstWider(BuiltinType::Kind First, BuiltinType::Kind Second) {
-  int FirstSize, SecondSize;
+  int FirstSize = 0, SecondSize = 0;
   if ((FirstSize = relativeIntSizes(First)) != 0 &&
       (SecondSize = relativeIntSizes(Second)) != 0)
     return FirstSize > SecondSize;

clang-tools-extra/clang-tidy/bugprone/MultipleNewInOneExpressionCheck.cpp

@@ -29,7 +29,7 @@ bool isExprValueStored(const Expr *E, ASTContext &C) {
   DynTypedNodeList P = PMap.getParents(*E);
   if (P.size() != 1)
     return false;
-  const Expr *ParentE;
+  const Expr *ParentE = nullptr;
   while ((ParentE = P[0].get<Expr>()) && ParentE->IgnoreParenCasts() == E) {
     P = PMap.getParents(P[0]);
     if (P.size() != 1)

clang-tools-extra/clang-tidy/bugprone/RedundantBranchConditionCheck.cpp

@@ -76,7 +76,7 @@ void RedundantBranchConditionCheck::check(const MatchFinder::MatchResult &Result
   const auto *CondVar = Result.Nodes.getNodeAs<VarDecl>(CondVarStr);
   const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>(FuncStr);
 
-  const DeclRefExpr *OuterIfVar, *InnerIfVar;
+  const DeclRefExpr *OuterIfVar = nullptr, *InnerIfVar = nullptr;
   if (const auto *Inner = Result.Nodes.getNodeAs<DeclRefExpr>(InnerIfVar1Str))
     InnerIfVar = Inner;
   else

clang-tools-extra/clang-tidy/bugprone/SignalHandlerCheck.cpp

@@ -480,7 +480,7 @@ bool SignalHandlerCheck::checkFunctionCPP14(
     return true;
   }
 
-  const FunctionDecl *FBody;
+  const FunctionDecl *FBody = nullptr;
   const Stmt *BodyS = FD->getBody(FBody);
   if (!BodyS)
     return false;