Internals: Cleanup empty string constructors for clang-tidy. No functional change.

src/V3Const.cpp

@@ -1977,8 +1977,8 @@ private:
 	}
 	if (m_doNConst && anyconst) {
 	    //UINFO(9,"  Display in  "<<nodep->text()<<endl);
-	    string newFormat = "";
+            string newFormat;
-	    string fmt = "";
+            string fmt;
 	    bool inPct = false;
 	    AstNode* argp = nodep->exprsp();
 	    string text = nodep->text();

src/V3EmitC.cpp

@@ -1559,7 +1559,7 @@ void EmitCStmts::displayNode(AstNode* nodep, AstScopeName* scopenamep,
     // Convert Verilog display to C printf formats
     // 		"%0t" becomes "%d"
     emitDispState.clear();
-    string vfmt = "";
+    string vfmt;
     string::const_iterator pos = vformat.begin();
     bool inPct = false;
     for (; pos != vformat.end(); ++pos) {
@@ -2242,7 +2242,7 @@ void EmitCStmts::emitVarSort(const VarSortMap& vmap, VarVec* sortedp) {
 void EmitCStmts::emitSortedVarList(const VarVec& anons,
                                    const VarVec& nonanons,
                                    const string& prefixIfImp) {
-    string curVarCmt = "";
+    string curVarCmt;
     // Output anons
     {
         int anonMembers = anons.size();

src/V3LinkDot.cpp

@@ -485,7 +485,7 @@ public:
 	    }
 	    baddot = ident;   // So user can see where they botched it
 	    okSymp = lookupSymp;
-	    string altIdent = "";
+            string altIdent;
 	    if (m_forPrearray) {
 		// GENFOR Begin is foo__BRA__##__KET__ after we've genloop unrolled,
 		// but presently should be just "foo".

src/V3LinkResolve.cpp

@@ -256,7 +256,7 @@ private:
 	// Check display arguments, return new format string
 	string newFormat;
 	bool inPct = false;
-	string fmt = "";
+        string fmt;
 	for (string::const_iterator it = format.begin(); it != format.end(); ++it) {
 	    char ch = *it;
 	    if (!inPct && ch=='%') {

src/V3PreProc.cpp

@@ -629,7 +629,7 @@ string V3PreProcImp::defineSubst(V3DefineRef* refp) {
 	}
     }
 
-    string out = "";
+    string out;
     {   // Parse substitution define using arguments
 	string argName;
 	bool quote = false;

src/V3Simulate.h

@@ -831,7 +831,7 @@ private:
 	if (m_params) {
 	    AstNode* nextArgp = nodep->exprsp();
 
-	    string result = "";
+            string result;
 	    string format = nodep->text();
 	    string::const_iterator pos = format.begin();
 	    bool inPct = false;

src/V3Task.cpp

@@ -969,7 +969,7 @@ private:
 	else if (ftaskNoInline) prefix = "__VnoInFunc_";
 	// Unless public, v3Descope will not uniquify function names even if duplicate per-scope,
 	// so make it unique now.
-	string suffix = "";  // So, make them unique
+        string suffix;  // So, make them unique
 	if (!nodep->taskPublic()) suffix = "_"+m_scopep->nameDotless();
 	AstCFunc* cfuncp = new AstCFunc(nodep->fileline(),
 					prefix + nodep->name() + suffix,

src/V3Undriven.cpp

@@ -76,7 +76,7 @@ private:
     inline bool drivenFlag(int bit) const { return m_drivenWhole || m_flags[bit*FLAGS_PER_BIT + FLAG_DRIVEN]; }
     enum BitNamesWhich { BN_UNUSED, BN_UNDRIVEN, BN_BOTH };
     string bitNames(BitNamesWhich which) {
-	string bits="";
+        string bits;
 	bool prev = false;
 	int msb = 0;
 	// bit==-1 loops below; we do one extra iteration so end with prev=false

src/VlcTop.cpp

@@ -238,7 +238,7 @@ void VlcTop::annotateOutputFiles(const string& dirname) {
 		    if (first) {
 			first = false;
 			// Multiple columns on same line; print line just once
-			string indent = "";
+                        string indent;
 			for (string::const_iterator pos=line.begin(); pos!=line.end() && isspace(*pos); ++pos) {
 			    indent += *pos;
 			}

src/verilog.y

@@ -3070,7 +3070,7 @@ dpi_import_export<nodep>:	// ==IEEE: dpi_import_export
 	;
 
 dpi_importLabelE<strp>:		// IEEE: part of dpi_import_export
-		/* empty */				{ static string s = ""; $$ = &s; }
+		/* empty */				{ static string s; $$ = &s; }
 	|	idAny/*c_identifier*/ '='		{ $$ = $1; $<fl>$=$<fl>1; }
 	;