diff --git a/include/verilated_cov.cpp b/include/verilated_cov.cpp
index df46d5d37..753e550cb 100644
--- a/include/verilated_cov.cpp
+++ b/include/verilated_cov.cpp
@@ -90,7 +90,7 @@ public:
 class VerilatedCovImp : VerilatedCovImpBase {
 private:
     // TYPES
-    typedef std::map<std::string, int> ValueIndexMap;
+    typedef std::map<const std::string, int> ValueIndexMap;
     typedef std::map<int, std::string> IndexValueMap;
     typedef std::deque<VerilatedCovImpItem*> ItemList;
 
@@ -350,7 +350,7 @@ public:
         os << "# SystemC::Coverage-3\n";
 
         // Build list of events; totalize if collapsing hierarchy
-        typedef std::map<std::string, std::pair<std::string, vluint64_t>> EventMap;
+        typedef std::map<const std::string, std::pair<std::string, vluint64_t>> EventMap;
         EventMap eventCounts;
         for (const auto& itemp : m_items) {
             std::string name;
diff --git a/include/verilated_heavy.h b/include/verilated_heavy.h
index 3d4795de0..43da92fc2 100644
--- a/include/verilated_heavy.h
+++ b/include/verilated_heavy.h
@@ -181,8 +181,7 @@ public:
     T_Value& at(const T_Key& index) {
         const auto it = m_map.find(index);
         if (it == m_map.end()) {
-            std::pair<typename Map::iterator, bool> pit
-                = m_map.insert(std::make_pair(index, m_defaultValue));
+            const auto pit = m_map.insert(std::make_pair(index, m_defaultValue));
             return pit.first->second;
         }
         return it->second;
diff --git a/include/verilated_vcd_c.h b/include/verilated_vcd_c.h
index 63b34ec55..e5e1b334a 100644
--- a/include/verilated_vcd_c.h
+++ b/include/verilated_vcd_c.h
@@ -76,7 +76,7 @@ private:
     std::vector<char> m_suffixes;  ///< VCD line end string codes + metadata
     const char* m_suffixesp;  ///< Pointer to first element of above
 
-    typedef std::map<std::string, std::string> NameMap;
+    typedef std::map<const std::string, const std::string> NameMap;
     NameMap* m_namemapp = nullptr;  ///< List of names for the header
 
     void bufferResize(vluint64_t minsize);
diff --git a/src/V3Ast.h b/src/V3Ast.h
index 47395909c..6ae97f107 100644
--- a/src/V3Ast.h
+++ b/src/V3Ast.h
@@ -2453,7 +2453,7 @@ class AstNodeUOrStructDType : public AstNodeDType {
     // A struct or union; common handling
 private:
     // TYPES
-    typedef std::map<string, AstMemberDType*> MemberNameMap;
+    typedef std::map<const string, AstMemberDType*> MemberNameMap;
     // MEMBERS
     string m_name;  // Name from upper typedef, if any
     bool m_packed;
diff --git a/src/V3AstNodes.h b/src/V3AstNodes.h
index ca16cf88f..34b3af025 100644
--- a/src/V3AstNodes.h
+++ b/src/V3AstNodes.h
@@ -300,7 +300,7 @@ public:
 
 class AstClass : public AstNodeModule {
     // TYPES
-    typedef std::map<string, AstNode*> MemberNameMap;
+    typedef std::map<const string, AstNode*> MemberNameMap;
     // MEMBERS
     MemberNameMap m_members;  // Members or method children
     AstClassPackage* m_packagep = nullptr;  // Class package this is under
diff --git a/src/V3CUse.cpp b/src/V3CUse.cpp
index 3c02364a1..88c1cbe20 100644
--- a/src/V3CUse.cpp
+++ b/src/V3CUse.cpp
@@ -41,7 +41,7 @@ private:
     // MEMBERS
     AstNodeModule* m_modInsertp;  // Current module to insert AstCUse under
     typedef std::pair<VUseType, string> UseString;
-    std::map<UseString, AstCUse*> m_didUse;  // What we already used
+    std::map<const UseString, AstCUse*> m_didUse;  // What we already used
 
     // NODE STATE
     // Entire netlist:
diff --git a/src/V3Config.cpp b/src/V3Config.cpp
index a1e12f5f0..d36880697 100644
--- a/src/V3Config.cpp
+++ b/src/V3Config.cpp
@@ -33,7 +33,7 @@
 // cache of resolved entities. Entities stored in this container need an update
 // function that takes a reference of this type to join multiple entities into one.
 template <typename T> class V3ConfigWildcardResolver {
-    typedef std::map<string, T> Map;
+    typedef std::map<const string, T> Map;
 
     Map m_mapWildcard;  // Wildcard strings to entities
     Map m_mapResolved;  // Resolved strings to converged entities
diff --git a/src/V3Delayed.cpp b/src/V3Delayed.cpp
index c042968f9..fdd23ec39 100644
--- a/src/V3Delayed.cpp
+++ b/src/V3Delayed.cpp
@@ -95,10 +95,10 @@ private:
     bool m_inDly = false;  // True in delayed assignments
     bool m_inLoop = false;  // True in for loops
     bool m_inInitial = false;  // True in initial blocks
-    typedef std::map<std::pair<AstNodeModule*, string>, AstVar*> VarMap;
+    typedef std::map<const std::pair<AstNodeModule*, string>, AstVar*> VarMap;
     VarMap m_modVarMap;  // Table of new var names created under module
     VDouble0 m_statSharedSet;  // Statistic tracking
-    typedef std::map<AstVarScope*, int> ScopeVecMap;
+    typedef std::map<const AstVarScope*, int> ScopeVecMap;
     ScopeVecMap m_scopeVecMap;  // Next var number for each scope
 
     // METHODS
diff --git a/src/V3EmitC.cpp b/src/V3EmitC.cpp
index c07416528..243c3314b 100644
--- a/src/V3EmitC.cpp
+++ b/src/V3EmitC.cpp
@@ -2874,7 +2874,7 @@ void EmitCStmts::emitVarSort(const VarSortMap& vmap, VarVec* sortedp) {
     }
 
     // MacroTask mode.  Sort by MTask-affinity group first, size second.
-    typedef std::map<MTaskIdSet, VarSortMap> MTaskVarSortMap;
+    typedef std::map<const MTaskIdSet, VarSortMap> MTaskVarSortMap;
     MTaskVarSortMap m2v;
     for (VarSortMap::const_iterator it = vmap.begin(); it != vmap.end(); ++it) {
         int size_class = it->first;
diff --git a/src/V3EmitCSyms.cpp b/src/V3EmitCSyms.cpp
index 9193c8a9c..de4bb2e43 100644
--- a/src/V3EmitCSyms.cpp
+++ b/src/V3EmitCSyms.cpp
@@ -71,13 +71,13 @@ class EmitCSyms : EmitCBaseVisitor {
             , m_modp{modp}
             , m_scopep{scopep} {}
     };
-    typedef std::map<string, ScopeFuncData> ScopeFuncs;
-    typedef std::map<string, ScopeVarData> ScopeVars;
-    typedef std::map<string, ScopeData> ScopeNames;
+    typedef std::map<const string, ScopeFuncData> ScopeFuncs;
+    typedef std::map<const string, ScopeVarData> ScopeVars;
+    typedef std::map<const string, ScopeData> ScopeNames;
     typedef std::pair<AstScope*, AstNodeModule*> ScopeModPair;
     typedef std::pair<AstNodeModule*, AstVar*> ModVarPair;
     typedef std::vector<string> ScopeNameList;
-    typedef std::map<string, ScopeNameList> ScopeNameHierarchy;
+    typedef std::map<const string, ScopeNameList> ScopeNameHierarchy;
     struct CmpName {
         inline bool operator()(const ScopeModPair& lhsp, const ScopeModPair& rhsp) const {
             return lhsp.first->name() < rhsp.first->name();
@@ -395,7 +395,7 @@ void EmitCSyms::emitSymHdr() {
 
     if (v3Global.dpi()) {
         puts("\n// DPI TYPES for DPI Export callbacks (Internal use)\n");
-        std::map<string, int> types;  // Remove duplicates and sort
+        std::map<const string, int> types;  // Remove duplicates and sort
         for (ScopeFuncs::iterator it = m_scopeFuncs.begin(); it != m_scopeFuncs.end(); ++it) {
             AstCFunc* funcp = it->second.m_funcp;
             if (funcp->dpiExport()) {
@@ -403,9 +403,7 @@ void EmitCSyms::emitSymHdr() {
                 types["typedef void (*" + cbtype + ") (" + cFuncArgs(funcp) + ");\n"] = 1;
             }
         }
-        for (std::map<string, int>::iterator it = types.begin(); it != types.end(); ++it) {
-            puts(it->first);
-        }
+        for (const auto& i : types) puts(i.first);
     }
 
     puts("\n// SYMS CLASS\n");
@@ -432,9 +430,9 @@ void EmitCSyms::emitSymHdr() {
     puts("bool __Vm_didInit;\n");
 
     puts("\n// SUBCELL STATE\n");
-    for (std::vector<ScopeModPair>::iterator it = m_scopes.begin(); it != m_scopes.end(); ++it) {
-        AstScope* scopep = it->first;
-        AstNodeModule* modp = it->second;
+    for (const auto& i : m_scopes) {
+        AstScope* scopep = i.first;
+        AstNodeModule* modp = i.second;
         if (VN_IS(modp, Class)) continue;
         if (modp->isTop()) {
             ofp()->printf("%-30s ", (prefixNameProtect(modp) + "*").c_str());
@@ -469,9 +467,9 @@ void EmitCSyms::emitSymHdr() {
     puts(symClassName() + "(" + topClassName() + "* topp, const char* namep);\n");
     puts(string("~") + symClassName() + "() {}\n");
 
-    for (std::map<int, bool>::iterator it = m_usesVfinal.begin(); it != m_usesVfinal.end(); ++it) {
-        puts("void " + symClassName() + "_" + cvtToStr(it->first) + "(");
-        if (it->second) {
+    for (const auto& i : m_usesVfinal) {
+        puts("void " + symClassName() + "_" + cvtToStr(i.first) + "(");
+        if (i.second) {
             puts("int __Vfinal");
         } else {
             puts(topClassName() + "* topp");
@@ -619,9 +617,9 @@ void EmitCSyms::emitSymImp() {
     puts("    , __Vm_didInit(false)\n");
     puts("    // Setup submodule names\n");
     char comma = ',';
-    for (std::vector<ScopeModPair>::iterator it = m_scopes.begin(); it != m_scopes.end(); ++it) {
-        AstScope* scopep = it->first;
-        AstNodeModule* modp = it->second;
+    for (const auto& i : m_scopes) {
+        AstScope* scopep = i.first;
+        AstNodeModule* modp = i.second;
         if (modp->isTop()) {
         } else {
             puts(string("    ") + comma + " " + protect(scopep->nameDotless()));
@@ -638,9 +636,9 @@ void EmitCSyms::emitSymImp() {
     puts("// Pointer to top level\n");
     puts("TOPp = topp;\n");
     puts("// Setup each module's pointers to their submodules\n");
-    for (std::vector<ScopeModPair>::iterator it = m_scopes.begin(); it != m_scopes.end(); ++it) {
-        AstScope* scopep = it->first;
-        AstNodeModule* modp = it->second;
+    for (const auto& i : m_scopes) {
+        AstScope* scopep = i.first;
+        AstNodeModule* modp = i.second;
         if (!modp->isTop()) {
             checkSplit(false);
             string arrow = scopep->name();
@@ -656,9 +654,9 @@ void EmitCSyms::emitSymImp() {
 
     puts("// Setup each module's pointer back to symbol table (for public functions)\n");
     puts("TOPp->" + protect("__Vconfigure") + "(this, true);\n");
-    for (std::vector<ScopeModPair>::iterator it = m_scopes.begin(); it != m_scopes.end(); ++it) {
-        AstScope* scopep = it->first;
-        AstNodeModule* modp = it->second;
+    for (const auto& i : m_scopes) {
+        AstScope* scopep = i.first;
+        AstNodeModule* modp = i.second;
         if (!modp->isTop()) {
             checkSplit(false);
             // first is used by AstCoverDecl's call to __vlCoverInsert
diff --git a/src/V3File.cpp b/src/V3File.cpp
index 4f5607494..465458a72 100644
--- a/src/V3File.cpp
+++ b/src/V3File.cpp
@@ -331,7 +331,7 @@ void V3File::createMakeDir() {
 // VInFilterImp
 
 class VInFilterImp {
-    typedef std::map<string, string> FileContentsMap;
+    typedef std::map<const string, string> FileContentsMap;
     typedef VInFilter::StrList StrList;
 
     FileContentsMap m_contentsMap;  // Cache of file contents
@@ -954,7 +954,7 @@ void V3OutCFile::putsGuard() {
 
 class VIdProtectImp {
     // MEMBERS
-    typedef std::map<string, string> IdMap;
+    typedef std::map<const string, string> IdMap;
     IdMap m_nameMap;  // Map of old name into new name
     typedef std::unordered_set<std::string> IdSet;
     IdSet m_newIdSet;  // Which new names exist
diff --git a/src/V3FileLine.h b/src/V3FileLine.h
index 85aa5500a..757a4275c 100644
--- a/src/V3FileLine.h
+++ b/src/V3FileLine.h
@@ -39,7 +39,7 @@ class FileLine;
 //! source file (each with its own unique filename number).
 class FileLineSingleton {
     // TYPES
-    typedef std::map<string, int> FileNameNumMap;
+    typedef std::map<const string, int> FileNameNumMap;
     // MEMBERS
     FileNameNumMap m_namemap;  // filenameno for each filename
     std::deque<string> m_names;  // filename text for each filenameno
diff --git a/src/V3Graph.cpp b/src/V3Graph.cpp
index 2ee8c5c9b..8001d55b6 100644
--- a/src/V3Graph.cpp
+++ b/src/V3Graph.cpp
@@ -335,7 +335,7 @@ void V3Graph::dumpDotFile(const string& filename, bool colorAsSubgraph) const {
 
     // We use a map here, as we don't want to corrupt anything (userp) in the graph,
     // and we don't care if this is slow.
-    std::map<V3GraphVertex*, int> numMap;
+    std::map<const V3GraphVertex*, int> numMap;
 
     // Print vertices
     int n = 0;
diff --git a/src/V3Hashed.cpp b/src/V3Hashed.cpp
index 9196a808d..22758e288 100644
--- a/src/V3Hashed.cpp
+++ b/src/V3Hashed.cpp
@@ -174,9 +174,8 @@ void V3Hashed::dumpFile(const string& filename, bool tree) {
     }
     *logp << "\n*** STATS:\n" << endl;
     *logp << "    #InBucket   Occurrences\n";
-    for (std::map<int, int>::iterator it = dist.begin(); it != dist.end(); ++it) {
-        *logp << "    " << std::setw(9) << it->first << "  " << std::setw(12) << it->second
-              << endl;
+    for (const auto& i : dist) {
+        *logp << "    " << std::setw(9) << i.first << "  " << std::setw(12) << i.second << endl;
     }
 
     *logp << "\n*** Dump:\n" << endl;
diff --git a/src/V3Inst.cpp b/src/V3Inst.cpp
index 4a7a9040f..a7dc03ee8 100644
--- a/src/V3Inst.cpp
+++ b/src/V3Inst.cpp
@@ -141,7 +141,7 @@ class InstDeModVarVisitor : public AstNVisitor {
     // Expand all module variables, and save names for later reference
 private:
     // STATE
-    typedef std::map<string, AstVar*> VarNameMap;
+    typedef std::map<const string, AstVar*> VarNameMap;
     VarNameMap m_modVarNameMap;  // Per module, name of cloned variables
 
     VL_DEBUG_FUNC;  // Declare debug()
diff --git a/src/V3LanguageWords.h b/src/V3LanguageWords.h
index 907095605..3764f2dce 100644
--- a/src/V3LanguageWords.h
+++ b/src/V3LanguageWords.h
@@ -27,7 +27,7 @@
 class V3LanguageWords {
     // List of common reserved keywords
 private:
-    typedef std::map<string, string> KeywordMap;
+    typedef std::map<const string, string> KeywordMap;
     struct Singleton {
         KeywordMap s_kwdMap;  // List of keywords, and what language applies
         Singleton() { init(); }
diff --git a/src/V3LifePost.cpp b/src/V3LifePost.cpp
index c3ba15bbd..f7fd88a83 100644
--- a/src/V3LifePost.cpp
+++ b/src/V3LifePost.cpp
@@ -183,9 +183,8 @@ private:
             return true;
         }
         if (before(assignPostLoc, loc)) return true;
-        for (std::set<LifeLocation>::iterator it = dlyVarAssigns.begin();
-             it != dlyVarAssigns.end(); ++it) {
-            if (!before(loc, *it)) return false;
+        for (const auto& i : dlyVarAssigns) {
+            if (!before(loc, i)) return false;
         }
         return true;
     }
diff --git a/src/V3LinkParse.cpp b/src/V3LinkParse.cpp
index b5595a81c..ebdc38cac 100644
--- a/src/V3LinkParse.cpp
+++ b/src/V3LinkParse.cpp
@@ -44,7 +44,7 @@ private:
     AstUser2InUse m_inuser2;
 
     // TYPES
-    typedef std::map<std::pair<void*, string>, AstTypedef*> ImplTypedefMap;
+    typedef std::map<const std::pair<void*, string>, AstTypedef*> ImplTypedefMap;
     typedef std::set<FileLine*> FileLineSet;
 
     // STATE
diff --git a/src/V3Options.cpp b/src/V3Options.cpp
index 9caff20c6..328554e75 100644
--- a/src/V3Options.cpp
+++ b/src/V3Options.cpp
@@ -53,7 +53,7 @@
 class V3OptionsImp {
 public:
     // TYPES
-    typedef std::map<string, std::set<string>> DirMap;  // Directory listing
+    typedef std::map<const string, std::set<string>> DirMap;  // Directory listing
 
     // STATE
     std::list<string> m_allArgs;  // List of every argument encountered
@@ -61,7 +61,7 @@ public:
     std::set<string> m_incDirUserSet;  // Include directories (for removing duplicates)
     std::list<string> m_incDirFallbacks;  // Include directories (ordered)
     std::set<string> m_incDirFallbackSet;  // Include directories (for removing duplicates)
-    std::map<string, V3LangCode> m_langExts;  // Language extension map
+    std::map<const string, V3LangCode> m_langExts;  // Language extension map
     std::list<string> m_libExtVs;  // Library extensions (ordered)
     std::set<string> m_libExtVSet;  // Library extensions (for removing duplicates)
     DirMap m_dirMap;  // Directory listing
@@ -346,10 +346,7 @@ void V3Options::checkParameters() {
     if (!m_parameters.empty()) {
         std::stringstream msg;
         msg << "Parameters from the command line were not found in the design:";
-        for (std::map<string, string>::iterator it = m_parameters.begin();
-             it != m_parameters.end(); ++it) {
-            msg << " " << it->first;
-        }
+        for (const auto& i : m_parameters) msg << " " << i.first;
         v3error(msg.str());
     }
 }
diff --git a/src/V3Options.h b/src/V3Options.h
index f5d21aac3..215fc85de 100644
--- a/src/V3Options.h
+++ b/src/V3Options.h
@@ -201,7 +201,7 @@ typedef std::set<string> V3StringSet;
 class V3HierarchicalBlockOption {
 public:
     // key:parameter name, value:value (as string)
-    typedef std::map<string, string> ParamStrMap;
+    typedef std::map<const string, string> ParamStrMap;
 
 private:
     string m_origName;  // module name
@@ -218,7 +218,7 @@ public:
     const ParamStrMap params() const { return m_parameters; }
 };
 
-typedef std::map<string, V3HierarchicalBlockOption> V3HierBlockOptSet;
+typedef std::map<const string, V3HierarchicalBlockOption> V3HierBlockOptSet;
 
 //######################################################################
 // V3Options - Command line options
@@ -227,7 +227,7 @@ class V3Options {
 public:
 private:
     // TYPES
-    typedef std::map<string, int> DebugSrcMap;
+    typedef std::map<const string, int> DebugSrcMap;
 
     // MEMBERS (general options)
     V3OptionsImp* m_impp;  // Slow hidden options
@@ -245,8 +245,8 @@ private:
     V3StringList m_forceIncs;   // argument: -FI
     DebugSrcMap m_debugSrcs;    // argument: --debugi-<srcfile>=<level>
     DebugSrcMap m_dumpTrees;    // argument: --dump-treei-<srcfile>=<level>
-    std::map<string,string> m_parameters;  // Parameters
-    std::map<string, V3HierarchicalBlockOption> m_hierBlocks;  // main switch: --hierarchical-block
+    std::map<const string, string> m_parameters;  // Parameters
+    std::map<const string, V3HierarchicalBlockOption> m_hierBlocks;  // main switch: --hierarchical-block
 
     bool m_preprocOnly = false;     // main switch: -E
     bool m_makePhony = false;       // main switch: -MP
diff --git a/src/V3Param.cpp b/src/V3Param.cpp
index 7c384c685..e8ae9d7a0 100644
--- a/src/V3Param.cpp
+++ b/src/V3Param.cpp
@@ -68,8 +68,8 @@
 class ParameterizedHierBlocks {
     typedef std::multimap<string, const V3HierarchicalBlockOption*> HierBlockOptsByOrigName;
     typedef HierBlockOptsByOrigName::const_iterator HierMapIt;
-    typedef std::map<string, AstNodeModule*> HierBlockModMap;
-    typedef std::map<string, AstConst*> ParamConstMap;
+    typedef std::map<const string, AstNodeModule*> HierBlockModMap;
+    typedef std::map<const string, AstConst*> ParamConstMap;
     typedef std::map<const V3HierarchicalBlockOption*, ParamConstMap> ParamsMap;
 
     // MEMBERS
@@ -218,17 +218,17 @@ private:
     typedef std::deque<std::pair<AstIfaceRefDType*, AstIfaceRefDType*>> IfaceRefRefs;
 
     // STATE
-    typedef std::map<AstNode*, AstNode*> CloneMap;
+    typedef std::map<const AstNode*, AstNode*> CloneMap;
     struct ModInfo {
         AstNodeModule* m_modp;  // Module with specified name
         CloneMap m_cloneMap;  // Map of old-varp -> new cloned varp
         explicit ModInfo(AstNodeModule* modp)
             : m_modp{modp} {}
     };
-    typedef std::map<string, ModInfo> ModNameMap;
+    typedef std::map<const string, ModInfo> ModNameMap;
     ModNameMap m_modNameMap;  // Hash of created module flavors by name
 
-    typedef std::map<string, string> LongMap;
+    typedef std::map<const string, string> LongMap;
     LongMap m_longMap;  // Hash of very long names to unique identity number
     int m_longId = 0;
 
@@ -237,7 +237,7 @@ private:
     V3StringSet m_allModuleNames;
 
     typedef std::pair<int, string> ValueMapValue;
-    typedef std::map<V3Hash, ValueMapValue> ValueMap;
+    typedef std::map<const V3Hash, ValueMapValue> ValueMap;
     ValueMap m_valueMap;  // Hash of node hash to (param value, name)
     int m_nextValue = 1;  // Next value to use in m_valueMap
 
@@ -370,7 +370,7 @@ private:
         }
     }
     void relinkPinsByName(AstPin* startpinp, AstNodeModule* modp) {
-        std::map<string, AstVar*> nameToPin;
+        std::map<const string, AstVar*> nameToPin;
         for (AstNode* stmtp = modp->stmtsp(); stmtp; stmtp = stmtp->nextp()) {
             if (AstVar* varp = VN_CAST(stmtp, Var)) {
                 if (varp->isIO() || varp->isGParam() || varp->isIfaceRef()) {
diff --git a/src/V3PreProc.cpp b/src/V3PreProc.cpp
index 022704efe..b43db96b9 100644
--- a/src/V3PreProc.cpp
+++ b/src/V3PreProc.cpp
@@ -108,7 +108,7 @@ public:
 class V3PreProcImp : public V3PreProc {
 public:
     // TYPES
-    typedef std::map<string, VDefine> DefinesMap;
+    typedef std::map<const string, VDefine> DefinesMap;
     typedef VInFilter::StrList StrList;
 
     // debug() -> see V3PreShellImp::debug; use --debugi-V3PreShell
@@ -585,7 +585,7 @@ string V3PreProcImp::defineSubst(VDefineRef* refp) {
     string value = defValue(refp->name());
     UINFO(4, "defineValue    '" << V3PreLex::cleanDbgStrg(value) << "'" << endl);
 
-    std::map<string, string> argValueByName;
+    std::map<const string, string> argValueByName;
     {  // Parse argument list into map
         unsigned numArgs = 0;
         string argName;
diff --git a/src/V3Simulate.h b/src/V3Simulate.h
index 5d6b4ccf5..b8baebd4d 100644
--- a/src/V3Simulate.h
+++ b/src/V3Simulate.h
@@ -61,7 +61,7 @@ public:
 };
 
 typedef std::deque<AstConst*> ConstDeque;
-typedef std::map<AstNodeDType*, ConstDeque> ConstPile;
+typedef std::map<const AstNodeDType*, ConstDeque> ConstPile;
 
 class SimulateVisitor : public AstNVisitor {
     // Simulate a node tree, returning value of variables
diff --git a/src/V3Stats.cpp b/src/V3Stats.cpp
index e2a954267..bb75f0e30 100644
--- a/src/V3Stats.cpp
+++ b/src/V3Stats.cpp
@@ -34,7 +34,7 @@ class StatsVisitor : public AstNVisitor {
 private:
     // NODE STATE/TYPES
 
-    typedef std::map<string, int> NameMap;  // Number of times a name appears
+    typedef std::map<const string, int> NameMap;  // Number of times a name appears
 
     // STATE
     string m_stage;  // Name of the stage we are scanning
diff --git a/src/V3Table.cpp b/src/V3Table.cpp
index b91348489..b83c44a68 100644
--- a/src/V3Table.cpp
+++ b/src/V3Table.cpp
@@ -222,7 +222,7 @@ private:
 
     void createTableVars(AstNode* nodep) {
         // Create table for each output
-        typedef std::map<string, int> NameCounts;
+        typedef std::map<const string, int> NameCounts;
         NameCounts namecounts;
         for (const AstVarScope* outvscp : m_outVarps) {
             AstVar* outvarp = outvscp->varp();
diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index c31598adb..ffe957a22 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -104,7 +104,7 @@ private:
 
     // TYPES
     typedef std::map<std::pair<AstScope*, AstVar*>, AstVarScope*> VarToScopeMap;
-    typedef std::map<AstNodeFTask*, AstClass*> FuncToClassMap;
+    typedef std::map<const AstNodeFTask*, AstClass*> FuncToClassMap;
     typedef std::vector<AstInitial*> Initials;
     // MEMBERS
     VarToScopeMap m_varToScopeMap;  // Map for Var -> VarScope mappings
@@ -341,7 +341,7 @@ private:
         IM_AFTER,  // Pointing at last inserted stmt, insert after
         IM_WHILE_PRECOND  // Pointing to for loop, add to body end
     };
-    typedef std::map<string, std::pair<AstNodeFTask*, string>> DpiNames;
+    typedef std::map<const string, std::pair<AstNodeFTask*, string>> DpiNames;
 
     // STATE
     TaskStateVisitor* m_statep;  // Common state between visitors
@@ -1388,7 +1388,7 @@ V3TaskConnects V3Task::taskConnects(AstNodeFTaskRef* nodep, AstNode* taskStmtsp)
     // Missing pin/expr?  We return (pinvar, nullptr)
     // Extra   pin/expr?  We clean it up
 
-    typedef std::map<string, int> NameToIndex;
+    typedef std::map<const string, int> NameToIndex;
     NameToIndex nameToIndex;
     V3TaskConnects tconnects;
     UASSERT_OBJ(nodep->taskp(), nodep, "unlinked");
diff --git a/src/V3Trace.cpp b/src/V3Trace.cpp
index 3aeace7ab..3b983055b 100644
--- a/src/V3Trace.cpp
+++ b/src/V3Trace.cpp
@@ -741,8 +741,8 @@ private:
 
         // Remove refs to traced values from TraceDecl nodes, these have now moved under
         // TraceInc
-        for (TraceVec::iterator it = traces.begin(); it != traces.end(); ++it) {
-            AstNode* const valuep = it->second->nodep()->valuep();
+        for (const auto& i : traces) {
+            AstNode* const valuep = i.second->nodep()->valuep();
             valuep->unlinkFrBack();
             valuep->deleteTree();
         }
diff --git a/src/V3Width.cpp b/src/V3Width.cpp
index acc745b75..aad9bc657 100644
--- a/src/V3Width.cpp
+++ b/src/V3Width.cpp
@@ -191,7 +191,7 @@ public:
 class WidthVisitor : public AstNVisitor {
 private:
     // TYPES
-    typedef std::map<std::pair<AstNodeDType*, AstAttrType>, AstVar*> TableMap;
+    typedef std::map<std::pair<const AstNodeDType*, AstAttrType>, AstVar*> TableMap;
     typedef std::map<int, AstPatMember*> PatVecMap;
 
     // STATE
@@ -1880,7 +1880,7 @@ private:
         // Assign missing values
         V3Number num(nodep, nodep->width(), 0);
         V3Number one(nodep, nodep->width(), 1);
-        std::map<V3Number, AstEnumItem*> inits;
+        std::map<const V3Number, AstEnumItem*> inits;
         for (AstEnumItem* itemp = nodep->itemsp(); itemp;
              itemp = VN_CAST(itemp->nextp(), EnumItem)) {
             if (itemp->valuep()) {
@@ -2982,7 +2982,7 @@ private:
         // which member each AstPatMember corresponds to before we can
         // determine the dtypep for that PatMember's value, and then
         // width the initial value appropriately.
-        typedef std::map<AstMemberDType*, AstPatMember*> PatMap;
+        typedef std::map<const AstMemberDType*, AstPatMember*> PatMap;
         PatMap patmap;
         {
             AstMemberDType* memp = vdtypep->membersp();
diff --git a/src/VlcPoint.h b/src/VlcPoint.h
index 83eefd85d..208dc5c56 100644
--- a/src/VlcPoint.h
+++ b/src/VlcPoint.h
@@ -93,7 +93,7 @@ public:
 class VlcPoints {
 private:
     // MEMBERS
-    typedef std::map<string, vluint64_t> NameMap;  // Sorted by name (ordered)
+    typedef std::map<const string, vluint64_t> NameMap;  // Sorted by name (ordered)
     NameMap m_nameMap;  //< Name to point-number
     std::vector<VlcPoint> m_points;  //< List of all points
     vluint64_t m_numPoints = 0;  //< Total unique points
diff --git a/src/VlcSource.h b/src/VlcSource.h
index 4f8e90e19..06d1cd847 100644
--- a/src/VlcSource.h
+++ b/src/VlcSource.h
@@ -101,7 +101,7 @@ public:
 class VlcSources {
 public:
     // TYPES
-    typedef std::map<string, VlcSource> NameMap;
+    typedef std::map<const string, VlcSource> NameMap;
 
 private:
     // MEMBERS