diff --git a/include/verilated.cpp b/include/verilated.cpp
index 97212fc49..1d69650da 100644
--- a/include/verilated.cpp
+++ b/include/verilated.cpp
@@ -1639,12 +1639,12 @@ std::string VL_TO_STRING_W(int words, WDataInP obj) {
 
 std::string VL_TOLOWER_NN(const std::string& ld) VL_MT_SAFE {
     std::string out = ld;
-    for (std::string::iterator it = out.begin(); it != out.end(); ++it) *it = tolower(*it);
+    for (auto& cr : out) cr = tolower(cr);
     return out;
 }
 std::string VL_TOUPPER_NN(const std::string& ld) VL_MT_SAFE {
     std::string out = ld;
-    for (std::string::iterator it = out.begin(); it != out.end(); ++it) *it = toupper(*it);
+    for (auto& cr : out) cr = toupper(cr);
     return out;
 }
 
@@ -1862,8 +1862,8 @@ void VlReadMem::setData(void* valuep, const std::string& rhs) {
     QData shift = m_hex ? 4ULL : 1ULL;
     bool innum = false;
     // Shift value in
-    for (std::string::const_iterator it = rhs.begin(); it != rhs.end(); ++it) {
-        char c = tolower(*it);
+    for (const auto& i : rhs) {
+        char c = tolower(i);
         int value = (c >= 'a' ? (c == 'x' ? VL_RAND_RESET_I(4) : (c - 'a' + 10)) : (c - '0'));
         if (m_bits <= 8) {
             CData* datap = reinterpret_cast<CData*>(valuep);
@@ -2312,7 +2312,7 @@ static void removeCb(Verilated::VoidPCb cb, void* datap, VoidPCbList& cbs) {
     cbs.remove(pair);
 }
 static void runCallbacks(VoidPCbList& cbs) VL_MT_SAFE {
-    for (VoidPCbList::iterator it = cbs.begin(); it != cbs.end(); ++it) { it->first(it->second); }
+    for (const auto& i : cbs) i.first(i.second);
 }
 
 void Verilated::addFlushCb(VoidPCb cb, void* datap) VL_MT_SAFE {
@@ -2445,9 +2445,7 @@ void VerilatedImp::internalsDump() VL_MT_SAFE {
     VL_PRINTF_MT("internalsDump:\n");
     versionDump();
     VL_PRINTF_MT("  Argv:");
-    for (ArgVec::const_iterator it = s_s.m_argVec.begin(); it != s_s.m_argVec.end(); ++it) {
-        VL_PRINTF_MT(" %s", it->c_str());
-    }
+    for (const auto& i : s_s.m_argVec) VL_PRINTF_MT(" %s", i.c_str());
     VL_PRINTF_MT("\n");
     scopesDump();
     exportsDump();
@@ -2675,7 +2673,7 @@ void VerilatedScope::varInsert(int finalize, const char* namep, void* datap, boo
 // cppcheck-suppress unusedFunction  // Used by applications
 VerilatedVar* VerilatedScope::varFind(const char* namep) const VL_MT_SAFE_POSTINIT {
     if (VL_LIKELY(m_varsp)) {
-        VerilatedVarNameMap::iterator it = m_varsp->find(namep);
+        const auto it = m_varsp->find(namep);
         if (VL_LIKELY(it != m_varsp->end())) return &(it->second);
     }
     return nullptr;
@@ -2708,9 +2706,7 @@ void VerilatedScope::scopeDump() const {
         }
     }
     if (VerilatedVarNameMap* varsp = this->varsp()) {
-        for (VerilatedVarNameMap::const_iterator it = varsp->begin(); it != varsp->end(); ++it) {
-            VL_PRINTF_MT("       VAR %p: %s\n", &(it->second), it->first);
-        }
+        for (const auto& i : *varsp) VL_PRINTF_MT("       VAR %p: %s\n", &(i.second), i.first);
     }
 }
 
diff --git a/include/verilated_cov.cpp b/include/verilated_cov.cpp
index ca8b9e688..df46d5d37 100644
--- a/include/verilated_cov.cpp
+++ b/include/verilated_cov.cpp
@@ -119,7 +119,7 @@ private:
     // PRIVATE METHODS
     int valueIndex(const std::string& value) VL_REQUIRES(m_mutex) {
         static int nextIndex = KEY_UNDEF + 1;
-        ValueIndexMap::iterator iter = m_valueIndexes.find(value);
+        const auto iter = m_valueIndexes.find(value);
         if (iter != m_valueIndexes.end()) return iter->second;
         nextIndex++;
         assert(nextIndex > 0);  // Didn't rollover
@@ -231,10 +231,7 @@ private:
 #undef SELF_CHECK
     }
     void clearGuts() VL_REQUIRES(m_mutex) {
-        for (ItemList::const_iterator it = m_items.begin(); it != m_items.end(); ++it) {
-            VerilatedCovImpItem* itemp = *(it);
-            VL_DO_DANGLING(delete itemp, itemp);
-        }
+        for (const auto& itemp : m_items) VL_DO_DANGLING(delete itemp, itemp);
         m_items.clear();
         m_indexValues.clear();
         m_valueIndexes.clear();
@@ -252,8 +249,7 @@ public:
         const VerilatedLockGuard lock(m_mutex);
         if (matchp && matchp[0]) {
             ItemList newlist;
-            for (ItemList::iterator it = m_items.begin(); it != m_items.end(); ++it) {
-                VerilatedCovImpItem* itemp = *(it);
+            for (const auto& itemp : m_items) {
                 if (!itemMatchesString(itemp, matchp)) {
                     VL_DO_DANGLING(delete itemp, itemp);
                 } else {
@@ -266,9 +262,7 @@ public:
     void zero() VL_EXCLUDES(m_mutex) {
         Verilated::quiesce();
         const VerilatedLockGuard lock(m_mutex);
-        for (ItemList::const_iterator it = m_items.begin(); it != m_items.end(); ++it) {
-            (*it)->zero();
-        }
+        for (const auto& itemp : m_items) itemp->zero();
     }
 
     // We assume there's always call to i/f/p in that order
@@ -358,8 +352,7 @@ public:
         // Build list of events; totalize if collapsing hierarchy
         typedef std::map<std::string, std::pair<std::string, vluint64_t>> EventMap;
         EventMap eventCounts;
-        for (ItemList::iterator it = m_items.begin(); it != m_items.end(); ++it) {
-            VerilatedCovImpItem* itemp = *(it);
+        for (const auto& itemp : m_items) {
             std::string name;
             std::string hier;
             bool per_instance = false;
@@ -390,7 +383,7 @@ public:
             // inefficient)
 
             // Find or insert the named event
-            EventMap::iterator cit = eventCounts.find(name);
+            const auto cit = eventCounts.find(name);
             if (cit != eventCounts.end()) {
                 const std::string& oldhier = cit->second.first;
                 cit->second.second += itemp->count();
@@ -401,11 +394,11 @@ public:
         }
 
         // Output body
-        for (EventMap::const_iterator it = eventCounts.begin(); it != eventCounts.end(); ++it) {
+        for (const auto& i : eventCounts) {
             os << "C '" << std::dec;
-            os << it->first;
-            if (!it->second.first.empty()) os << keyValueFormatter(VL_CIK_HIER, it->second.first);
-            os << "' " << it->second.second;
+            os << i.first;
+            if (!i.second.first.empty()) os << keyValueFormatter(VL_CIK_HIER, i.second.first);
+            os << "' " << i.second.second;
             os << std::endl;
         }
     }
diff --git a/include/verilated_fst_c.cpp b/include/verilated_fst_c.cpp
index b3ce35958..80c149abc 100644
--- a/include/verilated_fst_c.cpp
+++ b/include/verilated_fst_c.cpp
@@ -80,7 +80,7 @@ void VerilatedFst::open(const char* filename) VL_MT_UNSAFE {
     VerilatedTrace<VerilatedFst>::traceInit();
 
     // Clear the scope stack
-    std::list<std::string>::iterator it = m_curScope.begin();
+    auto it = m_curScope.begin();
     while (it != m_curScope.end()) {
         fstWriterSetUpscope(m_fst);
         it = m_curScope.erase(it);
@@ -89,10 +89,7 @@ void VerilatedFst::open(const char* filename) VL_MT_UNSAFE {
     // convert m_code2symbol into an array for fast lookup
     if (!m_symbolp) {
         m_symbolp = new fstHandle[nextCode()];
-        for (Code2SymbolType::iterator it = m_code2symbol.begin(); it != m_code2symbol.end();
-             ++it) {
-            m_symbolp[it->first] = it->second;
-        }
+        for (const auto& i : m_code2symbol) m_symbolp[i.first] = i.second;
     }
     m_code2symbol.clear();
 
@@ -140,8 +137,8 @@ void VerilatedFst::declare(vluint32_t code, const char* name, int dtypenum, fstV
     tokens.insert(tokens.begin(), moduleName());  // Add current module to the hierarchy
 
     // Find point where current and new scope diverge
-    std::list<std::string>::iterator cur_it = m_curScope.begin();
-    std::list<std::string>::iterator new_it = tokens.begin();
+    auto cur_it = m_curScope.begin();
+    auto new_it = tokens.begin();
     while (cur_it != m_curScope.end() && new_it != tokens.end()) {
         if (*cur_it != *new_it) break;
         ++cur_it;
@@ -171,7 +168,7 @@ void VerilatedFst::declare(vluint32_t code, const char* name, int dtypenum, fstV
         fstWriterEmitEnumTableRef(m_fst, enumNum);
     }
 
-    Code2SymbolType::const_iterator it = m_code2symbol.find(code);
+    const auto it = vlstd::as_const(m_code2symbol).find(code);
     if (it == m_code2symbol.end()) {  // New
         m_code2symbol[code]
             = fstWriterCreateVar(m_fst, vartype, vardir, bits, name_str.c_str(), 0);
diff --git a/include/verilated_heavy.h b/include/verilated_heavy.h
index f67e234bc..eb43fe595 100644
--- a/include/verilated_heavy.h
+++ b/include/verilated_heavy.h
@@ -145,21 +145,21 @@ public:
     int exists(const T_Key& index) const { return m_map.find(index) != m_map.end(); }
     // Return first element.  Verilog: function int first(ref index);
     int first(T_Key& indexr) const {
-        typename Map::const_iterator it = m_map.begin();
+        const auto it = m_map.cbegin();
         if (it == m_map.end()) return 0;
         indexr = it->first;
         return 1;
     }
     // Return last element.  Verilog: function int last(ref index)
     int last(T_Key& indexr) const {
-        typename Map::const_reverse_iterator it = m_map.rbegin();
+        const auto it = m_map.crbegin();
         if (it == m_map.rend()) return 0;
         indexr = it->first;
         return 1;
     }
     // Return next element. Verilog: function int next(ref index)
     int next(T_Key& indexr) const {
-        typename Map::const_iterator it = m_map.find(indexr);
+        auto it = m_map.find(indexr);
         if (VL_UNLIKELY(it == m_map.end())) return 0;
         ++it;
         if (VL_UNLIKELY(it == m_map.end())) return 0;
@@ -168,7 +168,7 @@ public:
     }
     // Return prev element. Verilog: function int prev(ref index)
     int prev(T_Key& indexr) const {
-        typename Map::const_iterator it = m_map.find(indexr);
+        auto it = m_map.find(indexr);
         if (VL_UNLIKELY(it == m_map.end())) return 0;
         if (VL_UNLIKELY(it == m_map.begin())) return 0;
         --it;
@@ -179,7 +179,7 @@ public:
     // Can't just overload operator[] or provide a "at" reference to set,
     // because we need to be able to insert only when the value is set
     T_Value& at(const T_Key& index) {
-        typename Map::iterator it = m_map.find(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));
@@ -189,7 +189,7 @@ public:
     }
     // Accessing. Verilog: v = assoc[index]
     const T_Value& at(const T_Key& index) const {
-        typename Map::iterator it = m_map.find(index);
+        const auto it = m_map.find(index);
         if (it == m_map.end()) {
             return m_defaultValue;
         } else {
@@ -204,8 +204,8 @@ public:
     std::string to_string() const {
         std::string out = "'{";
         std::string comma;
-        for (typename Map::const_iterator it = m_map.begin(); it != m_map.end(); ++it) {
-            out += comma + VL_TO_STRING(it->first) + ":" + VL_TO_STRING(it->second);
+        for (const auto& i : m_map) {
+            out += comma + VL_TO_STRING(i.first) + ":" + VL_TO_STRING(i.second);
             comma = ", ";
         }
         // Default not printed - maybe random init data
@@ -239,10 +239,9 @@ void VL_WRITEMEM_N(bool hex, int bits, const std::string& filename,
                    const VlAssocArray<T_Key, T_Value>& obj, QData start, QData end) VL_MT_SAFE {
     VlWriteMem wmem(hex, bits, filename, start, end);
     if (VL_UNLIKELY(!wmem.isOpen())) return;
-    for (typename VlAssocArray<T_Key, T_Value>::const_iterator it = obj.begin(); it != obj.end();
-         ++it) {
-        QData addr = it->first;
-        if (addr >= start && addr <= end) wmem.print(addr, true, &(it->second));
+    for (const auto& i : obj) {
+        QData addr = i.first;
+        if (addr >= start && addr <= end) wmem.print(addr, true, &(i.second));
     }
 }
 
@@ -361,8 +360,8 @@ public:
     std::string to_string() const {
         std::string out = "'{";
         std::string comma;
-        for (typename Deque::const_iterator it = m_deque.begin(); it != m_deque.end(); ++it) {
-            out += comma + VL_TO_STRING(*it);
+        for (const auto& i : m_deque) {
+            out += comma + VL_TO_STRING(i);
             comma = ", ";
         }
         return out + "} ";
diff --git a/include/verilated_imp.h b/include/verilated_imp.h
index 905b42e3a..515d221c8 100644
--- a/include/verilated_imp.h
+++ b/include/verilated_imp.h
@@ -112,7 +112,7 @@ public:
             // Unfortunately to release the lock we need to copy the message
             // (Or have the message be a pointer, but then new/delete cost on each message)
             // We assume messages are small, so copy
-            auto it = m_queue.begin();
+            const auto it = m_queue.begin();
             const VerilatedMsg msg = *(it);
             m_queue.erase(it);
             m_mutex.unlock();
@@ -284,9 +284,9 @@ public:
                         "%Error: Verilog called $test$plusargs or $value$plusargs without"
                         " testbench C first calling Verilated::commandArgs(argc,argv).");
         }
-        for (ArgVec::const_iterator it = s_s.m_argVec.begin(); it != s_s.m_argVec.end(); ++it) {
-            if ((*it)[0] == '+') {
-                if (0 == strncmp(prefixp, it->c_str() + 1, len)) return *it;
+        for (const auto& i : s_s.m_argVec) {
+            if (i[0] == '+') {
+                if (0 == strncmp(prefixp, i.c_str() + 1, len)) return i;
             }
         }
         return "";
@@ -305,7 +305,7 @@ public:
     // per map overhead * N scopes would take much more space and cache thrashing.
     static inline void userInsert(const void* scopep, void* userKey, void* userData) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_userMapMutex);
-        UserMap::iterator it = s_s.m_userMap.find(std::make_pair(scopep, userKey));
+        const auto it = s_s.m_userMap.find(std::make_pair(scopep, userKey));
         if (it != s_s.m_userMap.end()) {
             it->second = userData;
         } else {
@@ -314,7 +314,7 @@ public:
     }
     static inline void* userFind(const void* scopep, void* userKey) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_userMapMutex);
-        UserMap::const_iterator it = s_s.m_userMap.find(std::make_pair(scopep, userKey));
+        const auto& it = vlstd::as_const(s_s.m_userMap).find(std::make_pair(scopep, userKey));
         if (VL_UNLIKELY(it == s_s.m_userMap.end())) return nullptr;
         return it->second;
     }
@@ -324,7 +324,7 @@ private:
     static void userEraseScope(const VerilatedScope* scopep) VL_MT_SAFE {
         // Slow ok - called once/scope on destruction, so we simply iterate.
         const VerilatedLockGuard lock(s_s.m_userMapMutex);
-        for (UserMap::iterator it = s_s.m_userMap.begin(); it != s_s.m_userMap.end();) {
+        for (auto it = s_s.m_userMap.begin(); it != s_s.m_userMap.end();) {
             if (it->first.first == scopep) {
                 s_s.m_userMap.erase(it++);
             } else {
@@ -335,13 +335,13 @@ private:
     static void userDump() VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_userMapMutex);  // Avoid it changing in middle of dump
         bool first = true;
-        for (UserMap::const_iterator it = s_s.m_userMap.begin(); it != s_s.m_userMap.end(); ++it) {
+        for (const auto& i : s_s.m_userMap) {
             if (first) {
                 VL_PRINTF_MT("  userDump:\n");
                 first = false;
             }
-            VL_PRINTF_MT("    DPI_USER_DATA scope %p key %p: %p\n", it->first.first,
-                         it->first.second, it->second);
+            VL_PRINTF_MT("    DPI_USER_DATA scope %p key %p: %p\n", i.first.first, i.first.second,
+                         i.second);
         }
     }
 
@@ -350,7 +350,7 @@ public:  // But only for verilated*.cpp
     static void scopeInsert(const VerilatedScope* scopep) VL_MT_SAFE {
         // Slow ok - called once/scope at construction
         const VerilatedLockGuard lock(s_s.m_nameMutex);
-        VerilatedScopeNameMap::iterator it = s_s.m_nameMap.find(scopep->name());
+        const auto it = s_s.m_nameMap.find(scopep->name());
         if (it == s_s.m_nameMap.end()) {
             s_s.m_nameMap.insert(it, std::make_pair(scopep->name(), scopep));
         }
@@ -358,7 +358,7 @@ public:  // But only for verilated*.cpp
     static inline const VerilatedScope* scopeFind(const char* namep) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_nameMutex);
         // If too slow, can assume this is only VL_MT_SAFE_POSINIT
-        VerilatedScopeNameMap::const_iterator it = s_s.m_nameMap.find(namep);
+        const auto& it = s_s.m_nameMap.find(namep);
         if (VL_UNLIKELY(it == s_s.m_nameMap.end())) return nullptr;
         return it->second;
     }
@@ -366,15 +366,14 @@ public:  // But only for verilated*.cpp
         // Slow ok - called once/scope at destruction
         const VerilatedLockGuard lock(s_s.m_nameMutex);
         userEraseScope(scopep);
-        VerilatedScopeNameMap::iterator it = s_s.m_nameMap.find(scopep->name());
+        const auto it = s_s.m_nameMap.find(scopep->name());
         if (it != s_s.m_nameMap.end()) s_s.m_nameMap.erase(it);
     }
     static void scopesDump() VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_nameMutex);
         VL_PRINTF_MT("  scopesDump:\n");
-        for (VerilatedScopeNameMap::const_iterator it = s_s.m_nameMap.begin();
-             it != s_s.m_nameMap.end(); ++it) {
-            const VerilatedScope* scopep = it->second;
+        for (const auto& i : s_s.m_nameMap) {
+            const VerilatedScope* scopep = i.second;
             scopep->scopeDump();
         }
         VL_PRINTF_MT("\n");
@@ -408,7 +407,7 @@ public:  // But only for verilated*.cpp
     static int exportInsert(const char* namep) VL_MT_SAFE {
         // Slow ok - called once/function at creation
         const VerilatedLockGuard lock(s_s.m_exportMutex);
-        ExportNameMap::iterator it = s_s.m_exportMap.find(namep);
+        const auto it = s_s.m_exportMap.find(namep);
         if (it == s_s.m_exportMap.end()) {
             s_s.m_exportMap.insert(it, std::make_pair(namep, s_s.m_exportNext++));
             return s_s.m_exportNext++;
@@ -418,7 +417,7 @@ public:  // But only for verilated*.cpp
     }
     static int exportFind(const char* namep) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_exportMutex);
-        ExportNameMap::const_iterator it = s_s.m_exportMap.find(namep);
+        const auto& it = s_s.m_exportMap.find(namep);
         if (VL_LIKELY(it != s_s.m_exportMap.end())) return it->second;
         std::string msg = (std::string("%Error: Testbench C called ") + namep
                            + " but no such DPI export function name exists in ANY model");
@@ -428,22 +427,20 @@ public:  // But only for verilated*.cpp
     static const char* exportName(int funcnum) VL_MT_SAFE {
         // Slowpath; find name for given export; errors only so no map to reverse-map it
         const VerilatedLockGuard lock(s_s.m_exportMutex);
-        for (ExportNameMap::const_iterator it = s_s.m_exportMap.begin();
-             it != s_s.m_exportMap.end(); ++it) {
-            if (it->second == funcnum) return it->first;
+        for (const auto& i : s_s.m_exportMap) {
+            if (i.second == funcnum) return i.first;
         }
         return "*UNKNOWN*";
     }
     static void exportsDump() VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_exportMutex);
         bool first = true;
-        for (ExportNameMap::const_iterator it = s_s.m_exportMap.begin();
-             it != s_s.m_exportMap.end(); ++it) {
+        for (const auto& i : s_s.m_exportMap) {
             if (first) {
                 VL_PRINTF_MT("  exportDump:\n");
                 first = false;
             }
-            VL_PRINTF_MT("    DPI_EXPORT_NAME %05d: %s\n", it->second, it->first);
+            VL_PRINTF_MT("    DPI_EXPORT_NAME %05d: %s\n", i.second, i.first);
         }
     }
     // We don't free up m_exportMap until the end, because we can't be sure
@@ -500,9 +497,7 @@ public:  // But only for verilated*.cpp
     static void fdFlush(IData fdi) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_fdMutex);
         const VerilatedFpList fdlist = fdToFpList(fdi);
-        for (VerilatedFpList::const_iterator it = fdlist.begin(); it != fdlist.end(); ++it) {
-            fflush(*it);
-        }
+        for (const auto& i : fdlist) fflush(i);
     }
     static IData fdSeek(IData fdi, IData offset, IData origin) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_fdMutex);
@@ -520,9 +515,9 @@ public:  // But only for verilated*.cpp
     static void fdWrite(IData fdi, const std::string& output) VL_MT_SAFE {
         const VerilatedLockGuard lock(s_s.m_fdMutex);
         const VerilatedFpList fdlist = fdToFpList(fdi);
-        for (VerilatedFpList::const_iterator it = fdlist.begin(); it != fdlist.end(); ++it) {
-            if (VL_UNLIKELY(!*it)) continue;
-            fwrite(output.c_str(), 1, output.size(), *it);
+        for (const auto& i : fdlist) {
+            if (VL_UNLIKELY(!i)) continue;
+            fwrite(output.c_str(), 1, output.size(), i);
         }
     }
     static void fdClose(IData fdi) VL_MT_SAFE {
diff --git a/include/verilated_save.h b/include/verilated_save.h
index 767d99589..adc65fa8d 100644
--- a/include/verilated_save.h
+++ b/include/verilated_save.h
@@ -252,10 +252,9 @@ VerilatedSerialize& operator<<(VerilatedSerialize& os, VlAssocArray<T_Key, T_Val
     os << rhs.atDefault();
     vluint32_t len = rhs.size();
     os << len;
-    for (typename VlAssocArray<T_Key, T_Value>::const_iterator it = rhs.begin(); it != rhs.end();
-         ++it) {
-        T_Key index = it->first;  // Copy to get around const_iterator
-        T_Value value = it->second;
+    for (const auto& i : rhs) {
+        T_Key index = i.first;  // Copy to get around const_iterator
+        T_Value value = i.second;
         os << index << value;
     }
     return os;
diff --git a/include/verilated_threads.cpp b/include/verilated_threads.cpp
index f45ae065d..4edd9db71 100644
--- a/include/verilated_threads.cpp
+++ b/include/verilated_threads.cpp
@@ -125,9 +125,9 @@ void VlThreadPool::setupProfilingClientThread() {
 
 void VlThreadPool::profileAppendAll(const VlProfileRec& rec) {
     const VerilatedLockGuard lk(m_mutex);
-    for (ProfileSet::iterator it = m_allProfiles.begin(); it != m_allProfiles.end(); ++it) {
+    for (const auto& profilep : m_allProfiles) {
         // Every thread's profile trace gets a copy of rec.
-        (*it)->emplace_back(rec);
+        profilep->emplace_back(rec);
     }
 }
 
@@ -152,13 +152,12 @@ void VlThreadPool::profileDump(const char* filenamep, vluint64_t ticksElapsed) {
     fprintf(fp, "VLPROF stat yields %" VL_PRI64 "u\n", VlMTaskVertex::yields());
 
     vluint32_t thread_id = 0;
-    for (ProfileSet::const_iterator pit = m_allProfiles.begin(); pit != m_allProfiles.end();
-         ++pit) {
+    for (const auto& pi : m_allProfiles) {
         ++thread_id;
 
         bool printing = false;  // False while in warmup phase
-        for (ProfileTrace::const_iterator eit = (*pit)->begin(); eit != (*pit)->end(); ++eit) {
-            switch (eit->m_type) {
+        for (const auto& ei : *pi) {
+            switch (ei.m_type) {
             case VlProfileRec::TYPE_BARRIER:  //
                 printing = true;
                 break;
@@ -168,9 +167,8 @@ void VlThreadPool::profileDump(const char* filenamep, vluint64_t ticksElapsed) {
                         "VLPROF mtask %d"
                         " start %" VL_PRI64 "u end %" VL_PRI64 "u elapsed %" VL_PRI64 "u"
                         " predict_time %u cpu %u on thread %u\n",
-                        eit->m_mtaskId, eit->m_startTime, eit->m_endTime,
-                        (eit->m_endTime - eit->m_startTime), eit->m_predictTime, eit->m_cpu,
-                        thread_id);
+                        ei.m_mtaskId, ei.m_startTime, ei.m_endTime,
+                        (ei.m_endTime - ei.m_startTime), ei.m_predictTime, ei.m_cpu, thread_id);
                 break;
             default: assert(false); break;  // LCOV_EXCL_LINE
             }
diff --git a/include/verilated_vcd_c.cpp b/include/verilated_vcd_c.cpp
index 6ae9b51e2..863195546 100644
--- a/include/verilated_vcd_c.cpp
+++ b/include/verilated_vcd_c.cpp
@@ -185,15 +185,15 @@ void VerilatedVcd::makeNameMap() {
     // If no scope was specified, prefix everything with a "top"
     // This comes from user instantiations with no name - IE Vtop("").
     bool nullScope = false;
-    for (NameMap::const_iterator it = m_namemapp->begin(); it != m_namemapp->end(); ++it) {
-        const std::string& hiername = it->first;
+    for (const auto& i : *m_namemapp) {
+        const std::string& hiername = i.first;
         if (!hiername.empty() && hiername[0] == '\t') nullScope = true;
     }
     if (nullScope) {
         NameMap* newmapp = new NameMap;
-        for (NameMap::const_iterator it = m_namemapp->begin(); it != m_namemapp->end(); ++it) {
-            const std::string& hiername = it->first;
-            const std::string& decl = it->second;
+        for (const auto& i : *m_namemapp) {
+            const std::string& hiername = i.first;
+            const std::string& decl = i.second;
             std::string newname = std::string("top");
             if (hiername[0] != '\t') newname += ' ';
             newname += hiername;
@@ -367,9 +367,9 @@ void VerilatedVcd::dumpHeader() {
 
     // Print the signal names
     const char* lastName = "";
-    for (NameMap::const_iterator it = m_namemapp->begin(); it != m_namemapp->end(); ++it) {
-        const std::string& hiernamestr = it->first;
-        const std::string& decl = it->second;
+    for (const auto& i : *m_namemapp) {
+        const std::string& hiernamestr = i.first;
+        const std::string& decl = i.second;
 
         // Determine difference between the old and new names
         const char* hiername = hiernamestr.c_str();
diff --git a/include/verilated_vpi.cpp b/include/verilated_vpi.cpp
index 09c1d7fa1..831402dad 100644
--- a/include/verilated_vpi.cpp
+++ b/include/verilated_vpi.cpp
@@ -445,21 +445,21 @@ public:
         VpioCbList& cbObjList = s_s.m_cbObjLists[cbp->reason()];
         // We do not remove it now as we may be iterating the list,
         // instead set to nullptr and will cleanup later
-        for (VpioCbList::iterator it = cbObjList.begin(); it != cbObjList.end(); ++it) {
-            if (*it == cbp) *it = nullptr;
+        for (auto& ir : cbObjList) {
+            if (ir == cbp) ir = nullptr;
         }
     }
     static void cbTimedRemove(VerilatedVpioCb* cbp) {
-        VpioTimedCbs::iterator it = s_s.m_timedCbs.find(std::make_pair(cbp->time(), cbp));
-        if (VL_LIKELY(it != s_s.m_timedCbs.end())) { s_s.m_timedCbs.erase(it); }
+        const auto it = s_s.m_timedCbs.find(std::make_pair(cbp->time(), cbp));
+        if (VL_LIKELY(it != s_s.m_timedCbs.end())) s_s.m_timedCbs.erase(it);
     }
     static void callTimedCbs() VL_MT_UNSAFE_ONE {
         assertOneCheck();
         QData time = VL_TIME_Q();
-        for (VpioTimedCbs::iterator it = s_s.m_timedCbs.begin(); it != s_s.m_timedCbs.end();) {
+        for (auto it = s_s.m_timedCbs.begin(); it != s_s.m_timedCbs.end();) {
             if (VL_UNLIKELY(it->first <= time)) {
                 VerilatedVpioCb* vop = it->second;
-                VpioTimedCbs::iterator last_it = it;
+                const auto last_it = it;
                 ++it;  // Timed callbacks are one-shot
                 s_s.m_timedCbs.erase(last_it);
                 VL_DEBUG_IF_PLI(VL_DBG_MSGF("- vpi: timed_callback %p\n", vop););
@@ -470,14 +470,14 @@ public:
         }
     }
     static QData cbNextDeadline() {
-        VpioTimedCbs::const_iterator it = s_s.m_timedCbs.begin();
-        if (VL_LIKELY(it != s_s.m_timedCbs.end())) return it->first;
+        const auto it = s_s.m_timedCbs.cbegin();
+        if (VL_LIKELY(it != s_s.m_timedCbs.cend())) return it->first;
         return ~0ULL;  // maxquad
     }
     static bool callCbs(vluint32_t reason) VL_MT_UNSAFE_ONE {
         VpioCbList& cbObjList = s_s.m_cbObjLists[reason];
         bool called = false;
-        for (VpioCbList::iterator it = cbObjList.begin(); it != cbObjList.end();) {
+        for (auto it = cbObjList.begin(); it != cbObjList.end();) {
             if (VL_UNLIKELY(!*it)) {  // Deleted earlier, cleanup
                 it = cbObjList.erase(it);
                 continue;
@@ -494,7 +494,7 @@ public:
         VpioCbList& cbObjList = s_s.m_cbObjLists[cbValueChange];
         typedef std::set<VerilatedVpioVar*> VpioVarSet;
         VpioVarSet update;  // set of objects to update after callbacks
-        for (VpioCbList::iterator it = cbObjList.begin(); it != cbObjList.end();) {
+        for (auto it = cbObjList.begin(); it != cbObjList.end();) {
             if (VL_UNLIKELY(!*it)) {  // Deleted earlier, cleanup
                 it = cbObjList.erase(it);
                 continue;
@@ -515,9 +515,7 @@ public:
                 }
             }
         }
-        for (VpioVarSet::const_iterator it = update.begin(); it != update.end(); ++it) {
-            memcpy((*it)->prevDatap(), (*it)->varDatap(), (*it)->entSize());
-        }
+        for (const auto& ip : update) { memcpy(ip->prevDatap(), ip->varDatap(), ip->entSize()); }
     }
 
     static VerilatedVpiError* error_info() VL_MT_UNSAFE_ONE;  // getter for vpi error info
@@ -1253,7 +1251,7 @@ vpiHandle vpi_iterate(PLI_INT32 type, vpiHandle object) {
         VerilatedVpioModule* vop = VerilatedVpioModule::castp(object);
         const VerilatedHierarchyMap* map = VerilatedImp::hierarchyMap();
         const VerilatedScope* mod = vop ? vop->scopep() : nullptr;
-        VerilatedHierarchyMap::const_iterator it = map->find(const_cast<VerilatedScope*>(mod));
+        const auto it = vlstd::as_const(map)->find(const_cast<VerilatedScope*>(mod));
         if (it == map->end()) return 0;
         return ((new VerilatedVpioModuleIter(it->second))->castVpiHandle());
     }
diff --git a/include/verilatedos.h b/include/verilatedos.h
index 536fa224a..4ababb153 100644
--- a/include/verilatedos.h
+++ b/include/verilatedos.h
@@ -488,6 +488,14 @@ typedef unsigned long long vluint64_t;  ///< 64-bit unsigned type
 #define VL_STRINGIFY(x) VL_STRINGIFY2(x)
 #define VL_STRINGIFY2(x) #x
 
+//=========================================================================
+// Conversions
+
+namespace vlstd {
+// C++17's std::as_const
+template <class T> T const& as_const(T& v) { return v; }
+};  // namespace vlstd
+
 //=========================================================================
 
 #endif  // Guard
diff --git a/src/V3Active.cpp b/src/V3Active.cpp
index c7a07315d..560ab2912 100644
--- a/src/V3Active.cpp
+++ b/src/V3Active.cpp
@@ -109,7 +109,7 @@ public:
         AstActive* activep = nullptr;
         AstSenTree* activeSenp = m_activeSens.find(sensesp);
         if (activeSenp) {
-            ActiveMap::iterator it = m_activeMap.find(activeSenp);
+            const auto it = m_activeMap.find(activeSenp);
             UASSERT(it != m_activeMap.end(), "Corrupt active map");
             activep = it->second;
         }
diff --git a/src/V3Ast.cpp b/src/V3Ast.cpp
index b222d87eb..33aeda69c 100644
--- a/src/V3Ast.cpp
+++ b/src/V3Ast.cpp
@@ -1267,8 +1267,6 @@ AstNodeDType* AstNode::findVoidDType() const {
 // AstNVisitor
 
 void AstNVisitor::doDeletes() {
-    for (std::vector<AstNode*>::iterator it = m_deleteps.begin(); it != m_deleteps.end(); ++it) {
-        (*it)->deleteTree();
-    }
+    for (AstNode* nodep : m_deleteps) nodep->deleteTree();
     m_deleteps.clear();
 }
diff --git a/src/V3Ast.h b/src/V3Ast.h
index 909e5aaa9..32ba8f4f6 100644
--- a/src/V3Ast.h
+++ b/src/V3Ast.h
@@ -2464,7 +2464,7 @@ public:
     void clearCache() { m_members.clear(); }
     void repairMemberCache();
     AstMemberDType* findMember(const string& name) const {
-        MemberNameMap::const_iterator it = m_members.find(name);
+        const auto it = m_members.find(name);
         return (it == m_members.end()) ? nullptr : it->second;
     }
     static int lsb() { return 0; }
diff --git a/src/V3AstNodes.cpp b/src/V3AstNodes.cpp
index aa00791ae..2e7ee6406 100644
--- a/src/V3AstNodes.cpp
+++ b/src/V3AstNodes.cpp
@@ -481,9 +481,9 @@ string AstVar::vlPropDecl(string propName) const {
         out += "static const int " + propName + "__ulims[";
         out += cvtToStr(ulims.size());
         out += "] = {";
-        std::vector<int>::const_iterator it = ulims.begin();
+        auto it = ulims.cbegin();
         out += cvtToStr(*it);
-        while (++it != ulims.end()) {
+        while (++it != ulims.cend()) {
             out += ", ";
             out += cvtToStr(*it);
         }
@@ -920,7 +920,7 @@ AstBasicDType* AstTypeTable::findInsertSameDType(AstBasicDType* nodep) {
     VBasicTypeKey key(nodep->width(), nodep->widthMin(), nodep->numeric(), nodep->keyword(),
                       nodep->nrange());
     DetailedMap& mapr = m_detailedMap;
-    DetailedMap::const_iterator it = mapr.find(key);
+    const auto it = mapr.find(key);
     if (it != mapr.end()) return it->second;
     mapr.insert(make_pair(key, nodep));
     nodep->generic(true);
diff --git a/src/V3AstNodes.h b/src/V3AstNodes.h
index 80a159b02..c5222666d 100644
--- a/src/V3AstNodes.h
+++ b/src/V3AstNodes.h
@@ -333,7 +333,7 @@ public:
     void clearCache() { m_members.clear(); }
     void repairCache();
     AstNode* findMember(const string& name) const {
-        MemberNameMap::const_iterator it = m_members.find(name);
+        const auto it = m_members.find(name);
         return (it == m_members.end()) ? nullptr : it->second;
     }
     bool isVirtual() const { return m_virtual; }
@@ -4728,7 +4728,7 @@ public:
     AstNode* addIndexValuep(uint32_t index, AstNode* newp) {
         // Returns old value, caller must garbage collect
         AstNode* oldp = nullptr;
-        KeyItemMap::iterator it = m_map.find(index);
+        const auto it = m_map.find(index);
         if (it != m_map.end()) {
             oldp = it->second->valuep();
             it->second->valuep(newp);
@@ -4740,7 +4740,7 @@ public:
         return oldp;
     }
     AstNode* getIndexValuep(uint32_t index) const {
-        KeyItemMap::const_iterator it = m_map.find(index);
+        const auto it = m_map.find(index);
         if (it == m_map.end()) {
             return nullptr;
         } else {
diff --git a/src/V3Branch.cpp b/src/V3Branch.cpp
index 0b7de7552..d2c75242c 100644
--- a/src/V3Branch.cpp
+++ b/src/V3Branch.cpp
@@ -108,8 +108,7 @@ private:
 
     // METHODS
     void calc_tasks() {
-        for (CFuncVec::iterator it = m_cfuncsp.begin(); it != m_cfuncsp.end(); ++it) {
-            AstCFunc* nodep = *it;
+        for (AstCFunc* nodep : m_cfuncsp) {
             if (!nodep->dontInline()) nodep->isInline(true);
         }
     }
diff --git a/src/V3Broken.cpp b/src/V3Broken.cpp
index fc4de04cf..b4e811342 100644
--- a/src/V3Broken.cpp
+++ b/src/V3Broken.cpp
@@ -54,7 +54,7 @@ public:
     static void deleted(const AstNode* nodep) {
         // Called by operator delete on any node - only if VL_LEAK_CHECKS
         if (debug() >= 9) cout << "-nodeDel:  " << cvtToHex(nodep) << endl;
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         UASSERT_OBJ(!(iter == s_nodes.end() || !(iter->second & FLAG_ALLOCATED)),
                     reinterpret_cast<const AstNode*>(nodep),
                     "Deleting AstNode object that was never tracked or already deleted");
@@ -67,7 +67,7 @@ public:
     static void addNewed(const AstNode* nodep) {
         // Called by operator new on any node - only if VL_LEAK_CHECKS
         if (debug() >= 9) cout << "-nodeNew:  " << cvtToHex(nodep) << endl;
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         UASSERT_OBJ(!(iter != s_nodes.end() && (iter->second & FLAG_ALLOCATED)), nodep,
                     "Newing AstNode object that is already allocated");
         if (iter == s_nodes.end()) {
@@ -78,7 +78,7 @@ public:
     static void setUnder(const AstNode* nodep, bool flag) {
         // Called by BrokenCheckVisitor when each node entered/exited
         if (!okIfLinkedTo(nodep)) return;
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         if (iter != s_nodes.end()) {
             iter->second &= ~FLAG_UNDER_NOW;
             if (flag) iter->second |= FLAG_UNDER_NOW;
@@ -89,7 +89,7 @@ public:
         // cppcheck-suppress knownConditionTrueFalse
         if (!linkable) return;  // save some time, else the map will get huge!
 #endif
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         if (VL_UNCOVERABLE(iter == s_nodes.end())) {
 #ifdef VL_LEAK_CHECKS
             nodep->v3fatalSrc("AstNode is in tree, but not allocated");
@@ -113,7 +113,7 @@ public:
         // Some generic node has a pointer to this node.  Is it allocated?
         // Use this when might not be in tree; otherwise use okIfLinkedTo().
 #ifdef VL_LEAK_CHECKS
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         if (iter == s_nodes.end()) return false;
         if (!(iter->second & FLAG_ALLOCATED)) return false;
 #endif
@@ -121,7 +121,7 @@ public:
     }
     static bool okIfLinkedTo(const AstNode* nodep) {
         // Some node in tree has a pointer to this node.  Is it kosher?
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         if (iter == s_nodes.end()) return false;
 #ifdef VL_LEAK_CHECKS
         if (!(iter->second & FLAG_ALLOCATED)) return false;
@@ -133,7 +133,7 @@ public:
     static bool okIfAbove(const AstNode* nodep) {
         // Must be linked to and below current node
         if (!okIfLinkedTo(nodep)) return false;
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         if (iter == s_nodes.end()) return false;
         if ((iter->second & FLAG_UNDER_NOW)) return false;
         return true;
@@ -141,7 +141,7 @@ public:
     static bool okIfBelow(const AstNode* nodep) {
         // Must be linked to and below current node
         if (!okIfLinkedTo(nodep)) return false;
-        NodeMap::iterator iter = s_nodes.find(nodep);
+        const auto iter = s_nodes.find(nodep);
         if (iter == s_nodes.end()) return false;
         if (!(iter->second & FLAG_UNDER_NOW)) return false;
         return true;
diff --git a/src/V3Cdc.cpp b/src/V3Cdc.cpp
index cbe2c3840..9ada2ccc3 100644
--- a/src/V3Cdc.cpp
+++ b/src/V3Cdc.cpp
@@ -543,9 +543,7 @@ private:
             }
         }
         stable_sort(report.begin(), report.end());
-        for (std::deque<string>::iterator it = report.begin(); it != report.end(); ++it) {
-            *ofp << *it;
-        }
+        for (const auto& line : report) *ofp << line;
     }
 
     void edgeDomainRecurse(CdcEitherVertex* vertexp, bool traceDests, int level) {
diff --git a/src/V3Combine.cpp b/src/V3Combine.cpp
index 3d4fbc95b..5a7181187 100644
--- a/src/V3Combine.cpp
+++ b/src/V3Combine.cpp
@@ -108,8 +108,8 @@ public:
     void deleteCall(AstCCall* nodep) {
         std::pair<CallMmap::iterator, CallMmap::iterator> eqrange
             = m_callMmap.equal_range(nodep->funcp());
-        for (CallMmap::iterator nextit = eqrange.first; nextit != eqrange.second;) {
-            CallMmap::iterator eqit = nextit++;
+        for (auto nextit = eqrange.first; nextit != eqrange.second;) {
+            const auto eqit = nextit++;
             AstCCall* callp = eqit->second;
             if (callp == nodep) {
                 m_callMmap.erase(eqit);
diff --git a/src/V3Config.cpp b/src/V3Config.cpp
index d205bb7a8..d801d901b 100644
--- a/src/V3Config.cpp
+++ b/src/V3Config.cpp
@@ -60,7 +60,7 @@ public:
     // Access an entity and resolve wildcards that match it
     T* resolve(const string& name) {
         // Lookup if it was resolved before, typically not
-        typename Map::iterator it = m_mapResolved.find(name);
+        auto it = m_mapResolved.find(name);
         if (VL_UNLIKELY(it != m_mapResolved.end())) { return &it->second; }
 
         T* newp = nullptr;
diff --git a/src/V3Const.cpp b/src/V3Const.cpp
index 57c4ef583..97083ccb5 100644
--- a/src/V3Const.cpp
+++ b/src/V3Const.cpp
@@ -1788,14 +1788,8 @@ private:
                         vec.push_back(senp);
                     }
                     stable_sort(vec.begin(), vec.end(), SenItemCmp());
-                    for (std::vector<AstSenItem*>::iterator it = vec.begin(); it != vec.end();
-                         ++it) {
-                        (*it)->unlinkFrBack();
-                    }
-                    for (std::vector<AstSenItem*>::iterator it = vec.begin(); it != vec.end();
-                         ++it) {
-                        nodep->addSensesp(*it);
-                    }
+                    for (const auto& ip : vec) ip->unlinkFrBack();
+                    for (const auto& ip : vec) nodep->addSensesp(ip);
                     break;
                 }
             }
diff --git a/src/V3Coverage.cpp b/src/V3Coverage.cpp
index b7460d460..3651fa6e6 100644
--- a/src/V3Coverage.cpp
+++ b/src/V3Coverage.cpp
@@ -140,7 +140,7 @@ private:
     string traceNameForLine(AstNode* nodep, const string& type) {
         string name = "vlCoverageLineTrace_" + nodep->fileline()->filebasenameNoExt() + "__"
                       + cvtToStr(nodep->fileline()->lineno()) + "_" + type;
-        VarNameMap::iterator it = m_varnames.find(name);
+        const auto it = m_varnames.find(name);
         if (it == m_varnames.end()) {
             m_varnames.insert(make_pair(name, 1));
         } else {
diff --git a/src/V3CoverageJoin.cpp b/src/V3CoverageJoin.cpp
index c78818f4b..94da008d7 100644
--- a/src/V3CoverageJoin.cpp
+++ b/src/V3CoverageJoin.cpp
@@ -54,20 +54,16 @@ private:
         // Note uses user4
         V3Hashed hashed;  // Duplicate code detection
         // Hash all of the original signals we toggle cover
-        for (ToggleList::iterator it = m_toggleps.begin(); it != m_toggleps.end(); ++it) {
-            AstCoverToggle* nodep = *it;
-            hashed.hashAndInsert(nodep->origp());
-        }
+        for (AstCoverToggle* nodep : m_toggleps) hashed.hashAndInsert(nodep->origp());
         // Find if there are any duplicates
-        for (ToggleList::iterator it = m_toggleps.begin(); it != m_toggleps.end(); ++it) {
-            AstCoverToggle* nodep = *it;
+        for (AstCoverToggle* nodep : m_toggleps) {
             // nodep->backp() is null if we already detected it's a duplicate and unlinked it.
             if (nodep->backp()) {
                 // Want to choose a base node, and keep finding duplicates that are identical.
                 // This prevents making chains where a->b, then c->d, then b->c, as we'll
                 // find a->b, a->c, a->d directly.
                 while (true) {
-                    V3Hashed::iterator dupit = hashed.findDuplicate(nodep->origp());
+                    const auto dupit = hashed.findDuplicate(nodep->origp());
                     if (dupit == hashed.end()) break;
                     //
                     AstNode* duporigp = hashed.iteratorNodep(dupit);
diff --git a/src/V3Dead.cpp b/src/V3Dead.cpp
index 10e547884..b13aaae6e 100644
--- a/src/V3Dead.cpp
+++ b/src/V3Dead.cpp
@@ -358,8 +358,7 @@ private:
     }
 
     void deadCheckCells() {
-        for (std::vector<AstCell*>::iterator it = m_cellsp.begin(); it != m_cellsp.end(); ++it) {
-            AstCell* cellp = *it;
+        for (AstCell* cellp : m_cellsp) {
             if (cellp->user1() == 0 && !cellp->modp()->stmtsp()) {
                 cellp->modp()->user1Inc(-1);
                 VL_DO_DANGLING(cellp->unlinkFrBack()->deleteTree(), cellp);
@@ -386,8 +385,7 @@ private:
 
     void deadCheckVar() {
         // Delete any unused varscopes
-        for (std::vector<AstVarScope*>::iterator it = m_vscsp.begin(); it != m_vscsp.end(); ++it) {
-            AstVarScope* vscp = *it;
+        for (AstVarScope* vscp : m_vscsp) {
             if (vscp->user1() == 0) {
                 UINFO(4, "  Dead " << vscp << endl);
                 std::pair<AssignMap::iterator, AssignMap::iterator> eqrange
diff --git a/src/V3Delayed.cpp b/src/V3Delayed.cpp
index 1a4d17a64..00fdfbaa4 100644
--- a/src/V3Delayed.cpp
+++ b/src/V3Delayed.cpp
@@ -120,7 +120,7 @@ private:
         AstVar* varp;
         AstNodeModule* addmodp = oldvarscp->scopep()->modp();
         // We need a new AstVar, but only one for all scopes, to match the new AstVarScope
-        VarMap::iterator it = m_modVarMap.find(make_pair(addmodp, name));
+        const auto it = m_modVarMap.find(make_pair(addmodp, name));
         if (it != m_modVarMap.end()) {
             // Created module's AstVar earlier under some other scope
             varp = it->second;
diff --git a/src/V3Descope.cpp b/src/V3Descope.cpp
index f451e482f..44788487d 100644
--- a/src/V3Descope.cpp
+++ b/src/V3Descope.cpp
@@ -148,7 +148,7 @@ private:
         for (FuncMmap::iterator it = m_modFuncs.begin(); it != m_modFuncs.end(); ++it) {
             string name = it->first;
             AstCFunc* topFuncp = it->second;
-            FuncMmap::iterator nextIt1 = it;
+            auto nextIt1 = it;
             ++nextIt1;
             bool moreOfSame1 = (nextIt1 != m_modFuncs.end() && nextIt1->first == name);
             if (moreOfSame1) {
@@ -171,7 +171,7 @@ private:
                      eachIt != m_modFuncs.end() && eachIt->first == name; ++eachIt) {
                     it = eachIt;
                     AstCFunc* funcp = eachIt->second;
-                    FuncMmap::iterator nextIt2 = eachIt;
+                    auto nextIt2 = eachIt;
                     ++nextIt2;
                     bool moreOfSame = (nextIt2 != m_modFuncs.end() && nextIt2->first == name);
                     UASSERT_OBJ(funcp->scopep(), funcp, "Not scoped");
diff --git a/src/V3EmitC.cpp b/src/V3EmitC.cpp
index 3f0ffd8c9..870fc5cb8 100644
--- a/src/V3EmitC.cpp
+++ b/src/V3EmitC.cpp
@@ -226,8 +226,7 @@ public:
 
         stable_sort(funcsp.begin(), funcsp.end(), CmpName());
 
-        for (FuncVec::iterator it = funcsp.begin(); it != funcsp.end(); ++it) {
-            const AstCFunc* funcp = *it;
+        for (const AstCFunc* funcp : funcsp) {
             ofp()->putsPrivate(funcp->declPrivate());
             if (!funcp->ifdef().empty()) puts("#ifdef " + funcp->ifdef() + "\n");
             if (funcp->isStatic().trueUnknown()) puts("static ");
@@ -1528,9 +1527,7 @@ class EmitCImp : EmitCStmts {
         puts("QData __req = false;  // Logically a bool\n");  // But not because it results in
                                                               // faster code
         bool gotOne = false;
-        for (std::vector<AstChangeDet*>::iterator it = m_blkChangeDetVec.begin();
-             it != m_blkChangeDetVec.end(); ++it) {
-            AstChangeDet* changep = *it;
+        for (AstChangeDet* changep : m_blkChangeDetVec) {
             if (changep->lhsp()) {
                 if (!gotOne) {  // Not a clocked block
                     puts("__req |= (");
@@ -1543,9 +1540,7 @@ class EmitCImp : EmitCStmts {
         if (gotOne) puts(");\n");
         if (gotOne && !v3Global.opt.protectIds()) {
             // puts("VL_DEBUG_IF( if (__req) cout<<\"- CLOCKREQ );");
-            for (std::vector<AstChangeDet*>::iterator it = m_blkChangeDetVec.begin();
-                 it != m_blkChangeDetVec.end(); ++it) {
-                AstChangeDet* nodep = *it;
+            for (AstChangeDet* nodep : m_blkChangeDetVec) {
                 if (nodep->lhsp()) {
                     puts("VL_DEBUG_IF( if(__req && (");
                     bool gotOneIgnore = false;
@@ -1854,8 +1849,7 @@ void EmitCStmts::emitVarCtors(bool* firstp) {
         ofp()->indentInc();
         puts("\n");
         puts("#if (SYSTEMC_VERSION>20011000)\n");  // SystemC 2.0.1 and newer
-        for (VarVec::iterator it = m_ctorVarsVec.begin(); it != m_ctorVarsVec.end(); ++it) {
-            const AstVar* varp = *it;
+        for (const AstVar* varp : m_ctorVarsVec) {
             bool isArray = !VN_CAST(varp->dtypeSkipRefp(), BasicDType);
             if (isArray) {
                 puts("// Skipping array: ");
@@ -2887,7 +2881,7 @@ void EmitCStmts::emitSortedVarList(const VarVec& anons, const VarVec& nonanons,
         }
         if (anonL1s != 1)
             puts("// Anonymous structures to workaround compiler member-count bugs\n");
-        VarVec::const_iterator it = anons.begin();
+        auto it = anons.cbegin();
         for (int l3 = 0; l3 < anonL3s && it != anons.end(); ++l3) {
             if (anonL3s != 1) puts("struct {\n");
             for (int l2 = 0; l2 < anonL2s && it != anons.end(); ++l2) {
diff --git a/src/V3EmitCSyms.cpp b/src/V3EmitCSyms.cpp
index 4878bede3..31e370a25 100644
--- a/src/V3EmitCSyms.cpp
+++ b/src/V3EmitCSyms.cpp
@@ -168,7 +168,7 @@ class EmitCSyms : EmitCBaseVisitor {
 
     void varHierarchyScopes(string scp) {
         while (!scp.empty()) {
-            ScopeNames::const_iterator scpit = m_vpiScopeCandidates.find(scp);
+            const auto scpit = m_vpiScopeCandidates.find(scp);
             if ((scpit != m_vpiScopeCandidates.end())
                 && (m_scopeNames.find(scp) == m_scopeNames.end())) {
                 m_scopeNames.insert(make_pair(scpit->second.m_symName, scpit->second));
@@ -704,8 +704,8 @@ void EmitCSyms::emitSymImp() {
                  ++lit) {
                 string fromname = scopeSymString(it->first);
                 string toname = scopeSymString(*lit);
-                ScopeNames::const_iterator from = m_scopeNames.find(fromname);
-                ScopeNames::const_iterator to = m_scopeNames.find(toname);
+                const auto from = vlstd::as_const(m_scopeNames).find(fromname);
+                const auto to = vlstd::as_const(m_scopeNames).find(toname);
                 UASSERT(from != m_scopeNames.end(), fromname + " not in m_scopeNames");
                 UASSERT(to != m_scopeNames.end(), toname + " not in m_scopeNames");
                 puts("__Vhier.add(");
@@ -859,8 +859,7 @@ void EmitCSyms::emitDpiHdr() {
 
     int firstExp = 0;
     int firstImp = 0;
-    for (std::vector<AstCFunc*>::iterator it = m_dpis.begin(); it != m_dpis.end(); ++it) {
-        AstCFunc* nodep = *it;
+    for (AstCFunc* nodep : m_dpis) {
         if (nodep->dpiExportWrapper()) {
             if (!firstExp++) puts("\n// DPI EXPORTS\n");
             puts("// DPI export" + ifNoProtect(" at " + nodep->fileline()->ascii()) + "\n");
@@ -909,8 +908,7 @@ void EmitCSyms::emitDpiImp() {
     puts("#include \"" + topClassName() + ".h\"\n");
     puts("\n");
 
-    for (std::vector<AstCFunc*>::iterator it = m_dpis.begin(); it != m_dpis.end(); ++it) {
-        AstCFunc* nodep = *it;
+    for (AstCFunc* nodep : m_dpis) {
         if (nodep->dpiExportWrapper()) {
             puts("#ifndef _VL_DPIDECL_" + nodep->name() + "\n");
             puts("#define _VL_DPIDECL_" + nodep->name() + "\n");
diff --git a/src/V3EmitMk.cpp b/src/V3EmitMk.cpp
index 27f50be50..4b67ba894 100644
--- a/src/V3EmitMk.cpp
+++ b/src/V3EmitMk.cpp
@@ -210,8 +210,7 @@ public:
         of.puts("# User .cpp files (from .cpp's on Verilator command line)\n");
         of.puts("VM_USER_CLASSES = \\\n");
         const V3StringSet& cppFiles = v3Global.opt.cppFiles();
-        for (V3StringSet::const_iterator it = cppFiles.begin(); it != cppFiles.end(); ++it) {
-            string cppfile = *it;
+        for (const auto& cppfile : cppFiles) {
             of.puts("\t" + V3Os::filenameNonExt(cppfile) + " \\\n");
             string dir = V3Os::filenameDir(cppfile);
             dirs.insert(dir);
@@ -220,9 +219,7 @@ public:
 
         of.puts("# User .cpp directories (from .cpp's on Verilator command line)\n");
         of.puts("VM_USER_DIR = \\\n");
-        for (V3StringSet::iterator it = dirs.begin(); it != dirs.end(); ++it) {
-            of.puts("\t" + *it + " \\\n");
-        }
+        for (const auto& i : dirs) of.puts("\t" + i + " \\\n");
         of.puts("\n");
 
         of.puts("\n### Default rules...\n");
diff --git a/src/V3EmitXml.cpp b/src/V3EmitXml.cpp
index 262dde0be..3d5e4e466 100644
--- a/src/V3EmitXml.cpp
+++ b/src/V3EmitXml.cpp
@@ -293,10 +293,9 @@ public:
         nodep->accept(*this);
         // Xml output
         m_os << "<module_files>\n";
-        for (std::deque<FileLine*>::iterator it = m_nodeModules.begin(); it != m_nodeModules.end();
-             ++it) {
-            m_os << "<file id=\"" << (*it)->filenameLetters() << "\" filename=\""
-                 << (*it)->filename() << "\" language=\"" << (*it)->language().ascii() << "\"/>\n";
+        for (const FileLine* ifp : m_nodeModules) {
+            m_os << "<file id=\"" << ifp->filenameLetters() << "\" filename=\"" << ifp->filename()
+                 << "\" language=\"" << ifp->language().ascii() << "\"/>\n";
         }
         m_os << "</module_files>\n";
     }
diff --git a/src/V3File.cpp b/src/V3File.cpp
index 6b003c6a7..b3df18c1a 100644
--- a/src/V3File.cpp
+++ b/src/V3File.cpp
@@ -149,26 +149,23 @@ inline void V3FileDependImp::writeDepend(const string& filename) {
     const std::unique_ptr<std::ofstream> ofp(V3File::new_ofstream(filename));
     if (ofp->fail()) v3fatal("Can't write " << filename);
 
-    for (std::set<DependFile>::iterator iter = m_filenameList.begin();
-         iter != m_filenameList.end(); ++iter) {
-        if (iter->target()) { *ofp << iter->filename() << " "; }
+    for (const DependFile& i : m_filenameList) {
+        if (i.target()) *ofp << i.filename() << " ";
     }
     *ofp << " : ";
     *ofp << v3Global.opt.bin();
     *ofp << " ";
 
-    for (std::set<DependFile>::iterator iter = m_filenameList.begin();
-         iter != m_filenameList.end(); ++iter) {
-        if (!iter->target()) { *ofp << iter->filename() << " "; }
+    for (const DependFile& i : m_filenameList) {
+        if (!i.target()) *ofp << i.filename() << " ";
     }
 
     *ofp << endl;
 
     if (v3Global.opt.makePhony()) {
         *ofp << endl;
-        for (std::set<DependFile>::iterator iter = m_filenameList.begin();
-             iter != m_filenameList.end(); ++iter) {
-            if (!iter->target()) { *ofp << iter->filename() << ":" << endl; }
+        for (const DependFile& i : m_filenameList) {
+            if (!i.target()) *ofp << i.filename() << ":" << endl;
         }
     }
 }
@@ -576,7 +573,7 @@ protected:
     friend class VInFilter;
     // Read file contents and return it
     bool readWholefile(const string& filename, StrList& outl) {
-        FileContentsMap::iterator it = m_contentsMap.find(filename);
+        const auto it = m_contentsMap.find(filename);
         if (it != m_contentsMap.end()) {
             outl.push_back(it->second);
             return true;
@@ -592,12 +589,12 @@ protected:
     }
     size_t listSize(StrList& sl) {
         size_t out = 0;
-        for (StrList::iterator it = sl.begin(); it != sl.end(); ++it) out += it->length();
+        for (const string& i : sl) out += i.length();
         return out;
     }
     string listString(StrList& sl) {
         string out;
-        for (StrList::iterator it = sl.begin(); it != sl.end(); ++it) out += *it;
+        for (const string& i : sl) out += i;
         return out;
     }
     // CONSTRUCTORS
@@ -984,7 +981,7 @@ public:
     // METHODS
     string passthru(const string& old) {
         if (!v3Global.opt.protectIds()) return old;
-        IdMap::iterator it = m_nameMap.find(old);
+        const auto it = m_nameMap.find(old);
         if (it != m_nameMap.end()) {
             // No way to go back and correct the older crypt name
             UASSERT(old == it->second,
@@ -997,7 +994,7 @@ public:
     }
     string protectIf(const string& old, bool doIt) {
         if (!v3Global.opt.protectIds() || old.empty() || !doIt) return old;
-        IdMap::iterator it = m_nameMap.find(old);
+        const auto it = m_nameMap.find(old);
         if (it != m_nameMap.end())
             return it->second;
         else {
diff --git a/src/V3FileLine.cpp b/src/V3FileLine.cpp
index 9ba9f91bb..42a68f2e8 100644
--- a/src/V3FileLine.cpp
+++ b/src/V3FileLine.cpp
@@ -58,7 +58,7 @@ string FileLineSingleton::filenameLetters(int fileno) {
 //! We associate a language with each source file, so we also set the default
 //! for this.
 int FileLineSingleton::nameToNumber(const string& filename) {
-    FileNameNumMap::const_iterator it = m_namemap.find(filename);
+    const auto it = vlstd::as_const(m_namemap).find(filename);
     if (VL_LIKELY(it != m_namemap.end())) return it->second;
     int num = m_names.size();
     m_names.push_back(filename);
@@ -454,7 +454,7 @@ void* FileLine::operator new(size_t size) {
 void FileLine::operator delete(void* objp, size_t size) {
     if (!objp) return;
     FileLine* flp = static_cast<FileLine*>(objp);
-    FileLineCheckSet::iterator it = fileLineLeakChecks.find(flp);
+    const auto it = fileLineLeakChecks.find(flp);
     if (it != fileLineLeakChecks.end()) {
         fileLineLeakChecks.erase(it);
     } else {
@@ -470,7 +470,7 @@ void FileLine::deleteAllRemaining() {
     // that way.  Unfortunately this makes our leak checking a big mess, so
     // only when leak checking we'll track them all and cleanup.
     while (true) {
-        FileLineCheckSet::iterator it = fileLineLeakChecks.begin();
+        const auto it = fileLineLeakChecks.begin();
         if (it == fileLineLeakChecks.end()) break;
         delete *it;
         // Operator delete will remove the iterated object from the list.
diff --git a/src/V3Gate.cpp b/src/V3Gate.cpp
index 38c2332c9..1e67d08af 100644
--- a/src/V3Gate.cpp
+++ b/src/V3Gate.cpp
@@ -983,8 +983,8 @@ public:
         hash(extra1p);
         hash(extra2p);
 
-        V3Hashed::iterator inserted = m_hashed.hashAndInsert(rhsp);
-        V3Hashed::iterator dupit = m_hashed.findDuplicate(rhsp, this);
+        const auto inserted = m_hashed.hashAndInsert(rhsp);
+        const auto dupit = m_hashed.findDuplicate(rhsp, this);
         // Even though rhsp was just inserted, V3Hashed::findDuplicate doesn't
         // return anything in the hash that has the same pointer (V3Hashed.cpp::findDuplicate)
         // So dupit is either a different, duplicate rhsp, or the end of the hash.
diff --git a/src/V3Global.cpp b/src/V3Global.cpp
index d18a26c2e..7faf26c5d 100644
--- a/src/V3Global.cpp
+++ b/src/V3Global.cpp
@@ -83,7 +83,7 @@ void V3Global::dumpCheckGlobalTree(const string& stagename, int newNumber, bool
 }
 
 const std::string& V3Global::ptrToId(const void* p) {
-    PtrToIdMap::iterator it = m_ptrToId.find(p);
+    auto it = m_ptrToId.find(p);
     if (it == m_ptrToId.end()) {
         std::ostringstream os;
         if (p) {
diff --git a/src/V3GraphAcyc.cpp b/src/V3GraphAcyc.cpp
index d57a54953..393b74754 100644
--- a/src/V3GraphAcyc.cpp
+++ b/src/V3GraphAcyc.cpp
@@ -189,10 +189,7 @@ public:
         : m_origGraphp{origGraphp}
         , m_origEdgeFuncp{edgeFuncp} {}
     ~GraphAcyc() {
-        for (std::vector<OrigEdgeList*>::iterator it = m_origEdgeDelp.begin();
-             it != m_origEdgeDelp.end(); ++it) {
-            delete (*it);
-        }
+        for (OrigEdgeList* ip : m_origEdgeDelp) delete ip;
         m_origEdgeDelp.clear();
     }
     void main();
@@ -476,10 +473,7 @@ void GraphAcyc::place() {
 
     // Process each edge in weighted order
     m_placeStep = 10;
-    for (std::vector<V3GraphEdge*>::iterator it = edges.begin(); it != edges.end(); ++it) {
-        V3GraphEdge* edgep = (*it);
-        placeTryEdge(edgep);
-    }
+    for (V3GraphEdge* edgep : edges) placeTryEdge(edgep);
 }
 
 void GraphAcyc::placeTryEdge(V3GraphEdge* edgep) {
diff --git a/src/V3GraphAlg.cpp b/src/V3GraphAlg.cpp
index 7ae0b241b..560f475df 100644
--- a/src/V3GraphAlg.cpp
+++ b/src/V3GraphAlg.cpp
@@ -487,9 +487,7 @@ void V3Graph::sortVertices() {
     }
     std::stable_sort(vertices.begin(), vertices.end(), GraphSortVertexCmp());
     this->verticesUnlink();
-    for (std::vector<V3GraphVertex*>::iterator it = vertices.begin(); it != vertices.end(); ++it) {
-        (*it)->verticesPushBack(this);
-    }
+    for (V3GraphVertex* ip : vertices) ip->verticesPushBack(this);
 }
 
 void V3Graph::sortEdges() {
diff --git a/src/V3GraphDfa.cpp b/src/V3GraphDfa.cpp
index 9157c283c..40fcaadee 100644
--- a/src/V3GraphDfa.cpp
+++ b/src/V3GraphDfa.cpp
@@ -182,7 +182,7 @@ private:
         // not depend on order of edges
         uint32_t hash = hashDfaOrigins(nfasWithInput);
 
-        std::pair<HashMap::iterator, HashMap::iterator> eqrange = m_hashMap.equal_range(hash);
+        const auto eqrange = m_hashMap.equal_range(hash);
         for (HashMap::iterator it = eqrange.first; it != eqrange.second; ++it) {
             DfaVertex* testp = it->second;
             if (compareDfaOrigins(nfasWithInput, testp)) {
diff --git a/src/V3GraphStream.h b/src/V3GraphStream.h
index 1056b965e..233184397 100644
--- a/src/V3GraphStream.h
+++ b/src/V3GraphStream.h
@@ -197,7 +197,7 @@ private:
             for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep = edgep->outNextp()) {
                 V3GraphVertex* toVertexp = edgep->top();
 
-                typename WaitingVertices::iterator it = m_waitingVertices.find(toVertexp);
+                const auto it = m_waitingVertices.find(toVertexp);
                 UASSERT_OBJ(it != m_waitingVertices.end(), toVertexp,
                             "Found edge into vertex not in waiting list.");
                 if (it->second.unblock()) {
@@ -209,7 +209,7 @@ private:
             for (V3GraphEdge* edgep = vertexp->inBeginp(); edgep; edgep = edgep->inNextp()) {
                 V3GraphVertex* fromVertexp = edgep->fromp();
 
-                typename WaitingVertices::iterator it = m_waitingVertices.find(fromVertexp);
+                const auto it = m_waitingVertices.find(fromVertexp);
                 UASSERT_OBJ(it != m_waitingVertices.end(), fromVertexp,
                             "Found edge into vertex not in waiting list.");
                 if (it->second.unblock()) {
diff --git a/src/V3HierBlock.cpp b/src/V3HierBlock.cpp
index 1b3bdf9a4..39435e078 100644
--- a/src/V3HierBlock.cpp
+++ b/src/V3HierBlock.cpp
@@ -377,7 +377,7 @@ V3HierBlockPlan::HierVector V3HierBlockPlan::hierBlocksSorted() const {
         for (V3HierBlock::HierBlockSet::const_iterator it = p.begin(); it != p.end(); ++it) {
             // Delete hblockp from parrents. If a parent does not have a child anymore, then it is
             // a leaf too.
-            const ChildrenMap::iterator parentIt = childrenOfHierBlock.find(*it);
+            const auto parentIt = childrenOfHierBlock.find(*it);
             UASSERT_OBJ(parentIt != childrenOfHierBlock.end(), (*it)->modp(), "must be included");
             const V3HierBlock::HierBlockSet::size_type erased = parentIt->second.erase(hblockp);
             UASSERT_OBJ(erased == 1, hblockp->modp(),
diff --git a/src/V3Inline.cpp b/src/V3Inline.cpp
index 00e3dd2bd..b6879a20d 100644
--- a/src/V3Inline.cpp
+++ b/src/V3Inline.cpp
@@ -174,7 +174,7 @@ private:
 
         // Iterate through all modules in bottom-up order.
         // Make a final inlining decision for each.
-        for (ModVec::reverse_iterator it = m_allMods.rbegin(); it != m_allMods.rend(); ++it) {
+        for (auto it = m_allMods.rbegin(); it != m_allMods.rend(); ++it) {
             AstNodeModule* modp = *it;
 
             // If we're going to inline some modules into this one,
diff --git a/src/V3Inst.cpp b/src/V3Inst.cpp
index 6419f98eb..7919c547f 100644
--- a/src/V3Inst.cpp
+++ b/src/V3Inst.cpp
@@ -164,7 +164,7 @@ public:
         m_modVarNameMap.insert(make_pair(nodep->name(), nodep));
     }
     AstVar* find(const string& name) {
-        VarNameMap::iterator it = m_modVarNameMap.find(name);
+        const auto it = m_modVarNameMap.find(name);
         if (it != m_modVarNameMap.end()) {
             return it->second;
         } else {
diff --git a/src/V3LanguageWords.h b/src/V3LanguageWords.h
index 3e571e3b2..a11a6a222 100644
--- a/src/V3LanguageWords.h
+++ b/src/V3LanguageWords.h
@@ -41,7 +41,7 @@ public:
     static const_iterator begin() { return s().s_kwdMap.begin(); }
     static const_iterator end() { return s().s_kwdMap.end(); }
     static string isKeyword(const string& kwd) {
-        KeywordMap::const_iterator it = s().s_kwdMap.find(kwd);
+        const auto it = vlstd::as_const(s().s_kwdMap).find(kwd);
         if (it == s().s_kwdMap.end()) return "";
         return it->second;
     }
diff --git a/src/V3Life.cpp b/src/V3Life.cpp
index 9c3ee4bc8..dff42a07e 100644
--- a/src/V3Life.cpp
+++ b/src/V3Life.cpp
@@ -55,10 +55,9 @@ public:
     ~LifeState() {
         V3Stats::addStatSum("Optimizations, Lifetime assign deletions", m_statAssnDel);
         V3Stats::addStatSum("Optimizations, Lifetime constant prop", m_statAssnCon);
-        for (std::vector<AstNode*>::iterator it = m_unlinkps.begin(); it != m_unlinkps.end();
-             ++it) {
-            (*it)->unlinkFrBack();
-            (*it)->deleteTree();
+        for (AstNode* ip : m_unlinkps) {
+            ip->unlinkFrBack();
+            ip->deleteTree();
         }
     }
     // METHODS
@@ -168,7 +167,7 @@ public:
         // Do we have a old assignment we can nuke?
         UINFO(4, "     ASSIGNof: " << nodep << endl);
         UINFO(7, "       new: " << assp << endl);
-        LifeMap::iterator it = m_map.find(nodep);
+        const auto it = m_map.find(nodep);
         if (it != m_map.end()) {
             checkRemoveAssign(it);
             it->second.simpleAssign(assp);
@@ -179,7 +178,7 @@ public:
     }
     void complexAssign(AstVarScope* nodep) {
         UINFO(4, "     clearof: " << nodep << endl);
-        LifeMap::iterator it = m_map.find(nodep);
+        const auto it = m_map.find(nodep);
         if (it != m_map.end()) {
             it->second.complexAssign();
         } else {
@@ -188,7 +187,7 @@ public:
     }
     void varUsageReplace(AstVarScope* nodep, AstVarRef* varrefp) {
         // Variable rvalue.  If it references a constant, we can simply replace it
-        LifeMap::iterator it = m_map.find(nodep);
+        const auto it = m_map.find(nodep);
         if (it != m_map.end()) {
             if (AstConst* constp = it->second.constNodep()) {
                 if (!varrefp->varp()->isSigPublic()) {
@@ -208,7 +207,7 @@ public:
         }
     }
     void complexAssignFind(AstVarScope* nodep) {
-        LifeMap::iterator it = m_map.find(nodep);
+        const auto it = m_map.find(nodep);
         if (it != m_map.end()) {
             UINFO(4, "     casfind: " << it->first << endl);
             it->second.complexAssign();
@@ -217,7 +216,7 @@ public:
         }
     }
     void consumedFind(AstVarScope* nodep) {
-        LifeMap::iterator it = m_map.find(nodep);
+        const auto it = m_map.find(nodep);
         if (it != m_map.end()) {
             it->second.consumed();
         } else {
@@ -254,7 +253,7 @@ public:
             if (it->second.setBeforeUse() && nodep->user1()) {
                 // Both branches set the var, we can remove the assignment before the IF.
                 UINFO(4, "DUALBRANCH " << nodep << endl);
-                LifeMap::iterator itab = m_map.find(nodep);
+                const auto itab = m_map.find(nodep);
                 if (itab != m_map.end()) checkRemoveAssign(itab);
             }
         }
diff --git a/src/V3LinkCells.cpp b/src/V3LinkCells.cpp
index 72617a00c..df69692b1 100644
--- a/src/V3LinkCells.cpp
+++ b/src/V3LinkCells.cpp
@@ -467,7 +467,7 @@ private:
     void readModNames() {
         // mangled_name, BlockOptions
         const V3HierBlockOptSet& hierBlocks = v3Global.opt.hierBlocks();
-        V3HierBlockOptSet::const_iterator hierIt = hierBlocks.find(v3Global.opt.topModule());
+        const auto hierIt = vlstd::as_const(hierBlocks).find(v3Global.opt.topModule());
         UASSERT((hierIt != hierBlocks.end()) == v3Global.opt.hierChild(),
                 "information of the top module must exist if --hierarchical-child is set");
         // Look at all modules, and store pointers to all module names
diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 1a67bd700..327e44154 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -396,7 +396,7 @@ public:
         return symp;
     }
     VSymEnt* getScopeSym(AstScope* nodep) {
-        NameScopeSymMap::iterator it = m_nameScopeSymMap.find(nodep->name());
+        const auto it = m_nameScopeSymMap.find(nodep->name());
         UASSERT_OBJ(it != m_nameScopeSymMap.end(), nodep,
                     "Scope never assigned a symbol entry '" << nodep->name() << "'");
         return it->second;
@@ -404,7 +404,7 @@ public:
     void implicitOkAdd(AstNodeModule* nodep, const string& varname) {
         // Mark the given variable name as being allowed to be implicitly declared
         if (nodep) {
-            ImplicitNameSet::iterator it = m_implicitNameSet.find(make_pair(nodep, varname));
+            const auto it = m_implicitNameSet.find(make_pair(nodep, varname));
             if (it == m_implicitNameSet.end()) {
                 m_implicitNameSet.insert(make_pair(nodep, varname));
             }
@@ -438,9 +438,7 @@ public:
         return ifacerefp;
     }
     void computeIfaceVarSyms() {
-        for (IfaceVarSyms::iterator it = m_ifaceVarSyms.begin(); it != m_ifaceVarSyms.end();
-             ++it) {
-            VSymEnt* varSymp = *it;
+        for (VSymEnt* varSymp : m_ifaceVarSyms) {
             AstVar* varp = varSymp ? VN_CAST(varSymp->nodep(), Var) : nullptr;
             UINFO(9, "  insAllIface se" << cvtToHex(varSymp) << " " << varp << endl);
             AstIfaceRefDType* ifacerefp = ifaceRefFromArray(varp->subDTypep());
@@ -507,7 +505,7 @@ public:
                 VSymEnt* lhsp = it->first;
                 VSymEnt* srcp = lhsp;
                 while (true) {  // Follow chain of aliases up to highest level non-alias
-                    ScopeAliasMap::iterator it2 = m_scopeAliasMap[samn].find(srcp);
+                    const auto it2 = m_scopeAliasMap[samn].find(srcp);
                     if (it2 != m_scopeAliasMap[samn].end()) {
                         srcp = it2->second;
                         continue;
diff --git a/src/V3LinkJump.cpp b/src/V3LinkJump.cpp
index 943b2f2d6..b37647628 100644
--- a/src/V3LinkJump.cpp
+++ b/src/V3LinkJump.cpp
@@ -255,8 +255,7 @@ private:
         UINFO(8, "   DISABLE " << nodep << endl);
         iterateChildren(nodep);
         AstNodeBlock* blockp = nullptr;
-        for (BlockStack::reverse_iterator it = m_blockStack.rbegin(); it != m_blockStack.rend();
-             ++it) {
+        for (auto it = m_blockStack.rbegin(); it != m_blockStack.rend(); ++it) {
             UINFO(9, "    UNDERBLK  " << *it << endl);
             if ((*it)->name() == nodep->name()) {
                 blockp = *it;
diff --git a/src/V3Localize.cpp b/src/V3Localize.cpp
index 59b36cda8..c9ee6b9f4 100644
--- a/src/V3Localize.cpp
+++ b/src/V3Localize.cpp
@@ -118,8 +118,7 @@ private:
         flags.setNodeFlags(nodep);
     }
     void moveVars() {
-        for (std::vector<AstVar*>::iterator it = m_varps.begin(); it != m_varps.end(); ++it) {
-            AstVar* nodep = *it;
+        for (AstVar* nodep : m_varps) {
             if (nodep->valuep()) clearOptimizable(nodep, "HasInitValue");
             if (!VarFlags(nodep).m_stdFuncAsn) clearStdOptimizable(nodep, "NoStdAssign");
             VarFlags flags(nodep);
diff --git a/src/V3Number.cpp b/src/V3Number.cpp
index ebe50b49e..cdeb13f22 100644
--- a/src/V3Number.cpp
+++ b/src/V3Number.cpp
@@ -567,8 +567,8 @@ string V3Number::displayed(AstNode* nodep, const string& vformat) const {
 }
 
 string V3Number::displayed(FileLine* fl, const string& vformat) const {
-    string::const_iterator pos = vformat.begin();
-    UASSERT(pos != vformat.end() && pos[0] == '%',
+    auto pos = vformat.cbegin();
+    UASSERT(pos != vformat.cend() && pos[0] == '%',
             "$display-like function with non format argument " << *this);
     ++pos;
     bool left = false;
@@ -2400,14 +2400,14 @@ V3Number& V3Number::opToLowerN(const V3Number& lhs) {
     NUM_ASSERT_OP_ARGS1(lhs);
     NUM_ASSERT_STRING_ARGS1(lhs);
     std::string out = lhs.toString();
-    for (std::string::iterator it = out.begin(); it != out.end(); ++it) { *it = tolower(*it); }
+    for (auto& cr : out) cr = tolower(cr);
     return setString(out);
 }
 V3Number& V3Number::opToUpperN(const V3Number& lhs) {
     NUM_ASSERT_OP_ARGS1(lhs);
     NUM_ASSERT_STRING_ARGS1(lhs);
     std::string out = lhs.toString();
-    for (std::string::iterator it = out.begin(); it != out.end(); ++it) { *it = toupper(*it); }
+    for (auto& cr : out) cr = toupper(cr);
     return setString(out);
 }
 
diff --git a/src/V3Options.cpp b/src/V3Options.cpp
index ae28b8ff8..1fa8e2be4 100644
--- a/src/V3Options.cpp
+++ b/src/V3Options.cpp
@@ -469,7 +469,7 @@ string V3Options::fileExists(const string& filename) {
     string dir = V3Os::filenameDir(filename);
     string basename = V3Os::filenameNonDir(filename);
 
-    V3OptionsImp::DirMap::iterator diriter = m_impp->m_dirMap.find(dir);
+    auto diriter = m_impp->m_dirMap.find(dir);
     if (diriter == m_impp->m_dirMap.end()) {
         // Read the listing
         m_impp->m_dirMap.insert(std::make_pair(dir, std::set<string>()));
@@ -484,7 +484,7 @@ string V3Options::fileExists(const string& filename) {
     }
     // Find it
     std::set<string>* filesetp = &(diriter->second);
-    std::set<string>::iterator fileiter = filesetp->find(basename);
+    const auto fileiter = filesetp->find(basename);
     if (fileiter == filesetp->end()) {
         return "";  // Not found
     }
@@ -495,9 +495,8 @@ string V3Options::fileExists(const string& filename) {
 }
 
 string V3Options::filePathCheckOneDir(const string& modname, const string& dirname) {
-    for (std::list<string>::iterator extIter = m_impp->m_libExtVs.begin();
-         extIter != m_impp->m_libExtVs.end(); ++extIter) {
-        string fn = V3Os::filenameFromDirBase(dirname, modname + *extIter);
+    for (const string& i : m_impp->m_libExtVs) {
+        string fn = V3Os::filenameFromDirBase(dirname, modname + i);
         string exists = fileExists(fn);
         if (exists != "") {
             // Strip ./, it just looks ugly
@@ -530,14 +529,12 @@ string V3Options::filePath(FileLine* fl, const string& modname, const string& la
     // Find a filename to read the specified module name,
     // using the incdir and libext's.
     // Return "" if not found.
-    for (std::list<string>::iterator dirIter = m_impp->m_incDirUsers.begin();
-         dirIter != m_impp->m_incDirUsers.end(); ++dirIter) {
-        string exists = filePathCheckOneDir(modname, *dirIter);
+    for (const string& dir : m_impp->m_incDirUsers) {
+        string exists = filePathCheckOneDir(modname, dir);
         if (exists != "") return exists;
     }
-    for (std::list<string>::iterator dirIter = m_impp->m_incDirFallbacks.begin();
-         dirIter != m_impp->m_incDirFallbacks.end(); ++dirIter) {
-        string exists = filePathCheckOneDir(modname, *dirIter);
+    for (const string& dir : m_impp->m_incDirFallbacks) {
+        string exists = filePathCheckOneDir(modname, dir);
         if (exists != "") return exists;
     }
 
@@ -568,19 +565,15 @@ void V3Options::filePathLookedMsg(FileLine* fl, const string& modname) {
                         << endl);
         }
         std::cerr << V3Error::warnMore() << "... Looked in:" << endl;
-        for (std::list<string>::iterator dirIter = m_impp->m_incDirUsers.begin();
-             dirIter != m_impp->m_incDirUsers.end(); ++dirIter) {
-            for (std::list<string>::iterator extIter = m_impp->m_libExtVs.begin();
-                 extIter != m_impp->m_libExtVs.end(); ++extIter) {
-                string fn = V3Os::filenameFromDirBase(*dirIter, modname + *extIter);
+        for (const string& dir : m_impp->m_incDirUsers) {
+            for (const string& ext : m_impp->m_libExtVs) {
+                string fn = V3Os::filenameFromDirBase(dir, modname + ext);
                 std::cerr << V3Error::warnMore() << "     " << fn << endl;
             }
         }
-        for (std::list<string>::iterator dirIter = m_impp->m_incDirFallbacks.begin();
-             dirIter != m_impp->m_incDirFallbacks.end(); ++dirIter) {
-            for (std::list<string>::iterator extIter = m_impp->m_libExtVs.begin();
-                 extIter != m_impp->m_libExtVs.end(); ++extIter) {
-                string fn = V3Os::filenameFromDirBase(*dirIter, modname + *extIter);
+        for (const string& dir : m_impp->m_incDirFallbacks) {
+            for (const string& ext : m_impp->m_libExtVs) {
+                string fn = V3Os::filenameFromDirBase(dir, modname + ext);
                 std::cerr << V3Error::warnMore() << "     " << fn << endl;
             }
         }
@@ -596,7 +589,7 @@ V3LangCode V3Options::fileLanguage(const string& filename) {
     string::size_type pos;
     if ((pos = ext.rfind('.')) != string::npos) {
         ext.erase(0, pos + 1);
-        std::map<string, V3LangCode>::iterator it = m_impp->m_langExts.find(ext);
+        const auto it = m_impp->m_langExts.find(ext);
         if (it != m_impp->m_langExts.end()) return it->second;
     }
     return m_defaultLanguage;
@@ -1816,7 +1809,7 @@ void V3Options::setDebugMode(int level) {
 }
 
 void V3Options::setDebugSrcLevel(const string& srcfile, int level) {
-    DebugSrcMap::iterator iter = m_debugSrcs.find(srcfile);
+    const auto iter = m_debugSrcs.find(srcfile);
     if (iter != m_debugSrcs.end()) {
         iter->second = level;
     } else {
@@ -1828,7 +1821,7 @@ int V3Options::debugSrcLevel(const string& srcfile_path, int default_level) {
     // For simplicity, calling functions can just use __FILE__ for srcfile.
     // That means though we need to cleanup the filename from ../Foo.cpp -> Foo
     string srcfile = V3Os::filenameNonDirExt(srcfile_path);
-    DebugSrcMap::iterator iter = m_debugSrcs.find(srcfile);
+    const auto iter = m_debugSrcs.find(srcfile);
     if (iter != m_debugSrcs.end()) {
         return iter->second;
     } else {
@@ -1837,7 +1830,7 @@ int V3Options::debugSrcLevel(const string& srcfile_path, int default_level) {
 }
 
 void V3Options::setDumpTreeLevel(const string& srcfile, int level) {
-    DebugSrcMap::iterator iter = m_dumpTrees.find(srcfile);
+    const auto iter = m_dumpTrees.find(srcfile);
     if (iter != m_dumpTrees.end()) {
         iter->second = level;
     } else {
@@ -1849,7 +1842,7 @@ int V3Options::dumpTreeLevel(const string& srcfile_path) {
     // For simplicity, calling functions can just use __FILE__ for srcfile.
     // That means though we need to cleanup the filename from ../Foo.cpp -> Foo
     string srcfile = V3Os::filenameNonDirExt(srcfile_path);
-    DebugSrcMap::iterator iter = m_dumpTrees.find(srcfile);
+    const auto iter = m_dumpTrees.find(srcfile);
     if (iter != m_dumpTrees.end()) {
         return iter->second;
     } else {
diff --git a/src/V3Order.cpp b/src/V3Order.cpp
index b87230714..80ab77e66 100644
--- a/src/V3Order.cpp
+++ b/src/V3Order.cpp
@@ -157,7 +157,7 @@ public:
     V3List<OrderMoveVertex*>& readyVertices() { return m_readyVertices; }
     static OrderMoveDomScope* findCreate(const AstSenTree* domainp, const AstScope* scopep) {
         const DomScopeKey key = make_pair(domainp, scopep);
-        DomScopeMap::iterator iter = s_dsMap.find(key);
+        const auto iter = s_dsMap.find(key);
         if (iter != s_dsMap.end()) {
             return iter->second;
         } else {
@@ -1222,10 +1222,7 @@ public:
             }
         }
         // Destruction
-        for (std::deque<OrderUser*>::iterator it = m_orderUserps.begin();
-             it != m_orderUserps.end(); ++it) {
-            delete *it;
-        }
+        for (OrderUser* ip : m_orderUserps) delete ip;
         m_graph.debug(V3Error::debugDefault());
     }
     void main(AstNode* nodep) { iterate(nodep); }
@@ -1573,9 +1570,7 @@ void OrderVisitor::processEdgeReport() {
 
     *logp << "Signals and their clock domains:" << endl;
     stable_sort(report.begin(), report.end());
-    for (std::deque<string>::iterator it = report.begin(); it != report.end(); ++it) {
-        *logp << (*it) << endl;
-    }
+    for (const string& i : report) *logp << i << endl;
 }
 
 void OrderVisitor::processMoveClear() {
@@ -1888,9 +1883,7 @@ void OrderVisitor::processMTasks() {
         const AstSenTree* last_domainp = nullptr;
         AstCFunc* leafCFuncp = nullptr;
         int leafStmts = 0;
-        for (MTaskState::Logics::iterator it = state.m_logics.begin(); it != state.m_logics.end();
-             ++it) {
-            const OrderLogicVertex* logicp = *it;
+        for (const OrderLogicVertex* logicp : state.m_logics) {
             if (logicp->domainp() != last_domainp) {
                 // Start a new leaf function.
                 leafCFuncp = nullptr;
diff --git a/src/V3Param.cpp b/src/V3Param.cpp
index ab46e7bf7..3e07a3de2 100644
--- a/src/V3Param.cpp
+++ b/src/V3Param.cpp
@@ -169,7 +169,7 @@ public:
                     AstConst* constp = VN_CAST(pinp->exprp(), Const);
                     UASSERT_OBJ(constp, pinp,
                                 "parameter for a hierarchical block must have been constified");
-                    ParamConstMap::const_iterator pIt = params.find(modvarp->name());
+                    const auto pIt = vlstd::as_const(params).find(modvarp->name());
                     UINFO(5, "Comparing " << modvarp->name() << " " << constp << std::endl);
                     if (pIt == params.end() || paramIdx >= params.size()
                         || !areSame(constp, pIt->second)) {
@@ -190,7 +190,7 @@ public:
         UASSERT_OBJ(modIt != m_hierBlockMod.end(), firstPinp,
                     hierIt->second->mangledName() << " is not found");
 
-        HierBlockModMap::const_iterator it = m_hierBlockMod.find(hierIt->second->mangledName());
+        const auto it = vlstd::as_const(m_hierBlockMod).find(hierIt->second->mangledName());
         if (it == m_hierBlockMod.end()) return nullptr;
         return it->second;
     }
@@ -309,7 +309,7 @@ private:
         // Force hash collisions -- for testing only
         if (VL_UNLIKELY(v3Global.opt.debugCollision())) hash = V3Hash();
         int num;
-        ValueMap::iterator it = m_valueMap.find(hash);
+        const auto it = m_valueMap.find(hash);
         if (it != m_valueMap.end() && it->second.second == key) {
             num = it->second.first;
         } else {
@@ -355,12 +355,12 @@ private:
             if (pinp->modVarp()) {
                 // Find it in the clone structure
                 // UINFO(8,"Clone find 0x"<<hex<<(uint32_t)pinp->modVarp()<<endl);
-                CloneMap::iterator cloneiter = clonemapp->find(pinp->modVarp());
+                const auto cloneiter = clonemapp->find(pinp->modVarp());
                 UASSERT_OBJ(cloneiter != clonemapp->end(), pinp,
                             "Couldn't find pin in clone list");
                 pinp->modVarp(VN_CAST(cloneiter->second, Var));
             } else if (pinp->modPTypep()) {
-                CloneMap::iterator cloneiter = clonemapp->find(pinp->modPTypep());
+                const auto cloneiter = clonemapp->find(pinp->modPTypep());
                 UASSERT_OBJ(cloneiter != clonemapp->end(), pinp,
                             "Couldn't find pin in clone list");
                 pinp->modPTypep(VN_CAST(cloneiter->second, ParamTypeDType));
@@ -380,7 +380,7 @@ private:
         }
         for (AstPin* pinp = startpinp; pinp; pinp = VN_CAST(pinp->nextp(), Pin)) {
             if (AstVar* varp = pinp->modVarp()) {
-                std::map<string, AstVar*>::const_iterator varIt = nameToPin.find(varp->name());
+                const auto varIt = vlstd::as_const(nameToPin).find(varp->name());
                 UASSERT_OBJ(varIt != nameToPin.end(), varp,
                             "Not found in " << modp->prettyNameQ());
                 pinp->modVarp(varIt->second);
@@ -444,7 +444,7 @@ private:
         // Hitting a cell adds to the appropriate level of this level-sorted list,
         // so since cells originally exist top->bottom we process in top->bottom order too.
         while (!m_todoModps.empty()) {
-            LevelModMap::iterator itm = m_todoModps.begin();
+            const auto itm = m_todoModps.cbegin();
             AstNodeModule* nodep = itm->second;
             m_todoModps.erase(itm);
             if (!nodep->user5SetOnce()) {  // Process once; note clone() must clear so we do it
@@ -457,8 +457,7 @@ private:
                 //
                 // Process interface cells, then non-interface which may ref an interface cell
                 for (int nonIf = 0; nonIf < 2; ++nonIf) {
-                    for (CellList::iterator it = m_cellps.begin(); it != m_cellps.end(); ++it) {
-                        AstCell* cellp = *it;
+                    for (AstCell* cellp : m_cellps) {
                         if ((nonIf == 0 && VN_IS(cellp->modp(), Iface))
                             || (nonIf == 1 && !VN_IS(cellp->modp(), Iface))) {
                             string fullName(m_modp->hierName());
@@ -469,8 +468,7 @@ private:
                         }
                     }
                 }
-                for (CellList::iterator it = m_cellps.begin(); it != m_cellps.end(); ++it) {
-                    AstCell* cellp = *it;
+                for (AstCell* cellp : m_cellps) {
                     if (string* genHierNamep = (string*)cellp->user5p()) {
                         cellp->user5p(nullptr);
                         VL_DO_DANGLING(delete genHierNamep, genHierNamep);
@@ -964,7 +962,7 @@ void ParamVisitor::visitCell(AstCell* nodep, const string& hierName) {
             // Shorter name is convenient for hierarchical block
             string newname = longname;
             if (longname.length() > 30 || srcModp->hierBlock()) {
-                LongMap::iterator iter = m_longMap.find(longname);
+                const auto iter = m_longMap.find(longname);
                 if (iter != m_longMap.end()) {
                     newname = iter->second;
                 } else {
@@ -983,7 +981,7 @@ void ParamVisitor::visitCell(AstCell* nodep, const string& hierName) {
             //
             // Already made this flavor?
             AstNodeModule* cellmodp = nullptr;
-            ModNameMap::iterator iter = m_modNameMap.find(newname);
+            auto iter = m_modNameMap.find(newname);
             if (iter != m_modNameMap.end()) cellmodp = iter->second.m_modp;
             if (!cellmodp) {
                 // Deep clone of new module
diff --git a/src/V3ParseSym.h b/src/V3ParseSym.h
index 660b38cc9..3837aa096 100644
--- a/src/V3ParseSym.h
+++ b/src/V3ParseSym.h
@@ -127,8 +127,7 @@ public:
     }
     void showUpward() {
         UINFO(1, "ParseSym Stack:\n");
-        for (SymStack::reverse_iterator it = m_sympStack.rbegin(); it != m_sympStack.rend();
-             ++it) {
+        for (auto it = m_sympStack.rbegin(); it != m_sympStack.rend(); ++it) {
             VSymEnt* symp = *it;
             UINFO(1, "    " << symp->nodep() << endl);
         }
diff --git a/src/V3Partition.cpp b/src/V3Partition.cpp
index ae4df51f4..6890dc13e 100644
--- a/src/V3Partition.cpp
+++ b/src/V3Partition.cpp
@@ -244,7 +244,7 @@ public:
         //
         // This generalizes to multiple seed nodes also.
         while (!m_pending.empty()) {
-            PropCpPendSet::reverse_iterator it = m_pending.rbegin();
+            const auto it = m_pending.rbegin();
             V3GraphVertex* updateMep = (*it).key();
             uint32_t cpGrowBy = (*it).value();
             m_pending.erase(it);
@@ -297,12 +297,12 @@ private:
         // Confirm that we only set each node's CP once.  That's an
         // important property of PartPropagateCp which allows it to be far
         // faster than a recursive algorithm on some graphs.
-        CpMap::iterator it = m_seen.find(vxp);
+        const auto it = m_seen.find(vxp);
         UASSERT_OBJ(it == m_seen.end(), vxp, "Set CP on node twice");
         m_seen[vxp] = cost;
     }
     uint32_t critPathCost(V3GraphVertex* vxp, GraphWay way) const {
-        CpMap::const_iterator it = m_cp.find(vxp);
+        const auto it = m_cp.find(vxp);
         if (it != m_cp.end()) return it->second;
         return 0;
     }
@@ -425,7 +425,7 @@ public:
             LogicMTask* mtaskp = dynamic_cast<LogicMTask*>(vxp);
             EdgeSet& edges = mtaskp->m_edges[way.invert()];
             // This is mtaskp's relative with longest !wayward inclusive CP:
-            EdgeSet::reverse_iterator edgeIt = edges.rbegin();
+            const auto edgeIt = edges.rbegin();
             uint32_t edgeCp = (*edgeIt).value();
             UASSERT_OBJ(edgeCp == cp, vxp, "CP doesn't match longest wayward edge");
         }
@@ -686,8 +686,7 @@ public:
              << " (should match the computed critical path cost (CP) for the graph)\n";
 
         // Dump
-        for (std::vector<const LogicMTask*>::iterator it = path.begin(); it != path.end(); ++it) {
-            const LogicMTask* mtaskp = *it;
+        for (const LogicMTask* mtaskp : path) {
             *osp << "begin mtask with cost " << mtaskp->cost() << endl;
             for (VxList::const_iterator lit = mtaskp->vertexListp()->begin();
                  lit != mtaskp->vertexListp()->end(); ++lit) {
@@ -1523,7 +1522,7 @@ private:
 
         // Don't make all NxN/2 possible pairs of prereqs, that's a lot
         // to cart around. Just make a few pairs.
-        std::vector<LogicMTask*>::iterator it = shortestPrereqs.begin();
+        auto it = shortestPrereqs.cbegin();
         for (unsigned i = 0; exhaustive || (i < 3); ++i) {
             if (it == shortestPrereqs.end()) break;
             LogicMTask* ap = *(it++);
@@ -1834,7 +1833,7 @@ private:
             rankIt->second.erase(mergedp);
 
             while (!rankIt->second.empty()) {
-                LogicMTaskSet::iterator begin = rankIt->second.begin();
+                const auto begin = rankIt->second.cbegin();
                 LogicMTask* donorp = *begin;
                 UASSERT_OBJ(donorp != mergedp, donorp, "Donor can't be merged edge");
                 rankIt->second.erase(begin);
@@ -2360,7 +2359,7 @@ void V3Partition::setupMTaskDeps(V3Graph* mtasksp, const Vx2MTaskMap* vx2mtaskp)
                 UASSERT(outp->weight() > 0, "Mtask not assigned weight");
                 const MTaskMoveVertex* top = dynamic_cast<MTaskMoveVertex*>(outp->top());
                 UASSERT(top, "MoveVertex not associated to mtask");
-                Vx2MTaskMap::const_iterator it = vx2mtaskp->find(top);
+                const auto it = vlstd::as_const(vx2mtaskp)->find(top);
                 UASSERT(it != vx2mtaskp->end(), "MTask map can't find id");
                 LogicMTask* otherMTaskp = it->second;
                 UASSERT(otherMTaskp, "nullptr other Mtask");
diff --git a/src/V3Partition.h b/src/V3Partition.h
index dde438302..231ebf8d2 100644
--- a/src/V3Partition.h
+++ b/src/V3Partition.h
@@ -86,7 +86,7 @@ public:
     PartPtrIdMap() {}
     // METHODS
     vluint64_t findId(const void* ptrp) const {
-        PtrMap::const_iterator it = m_id.find(ptrp);
+        const auto it = m_id.find(ptrp);
         if (it != m_id.end()) return it->second;
         m_id[ptrp] = m_nextId;
         return m_nextId++;
diff --git a/src/V3PreProc.cpp b/src/V3PreProc.cpp
index 1adbf78de..8653ad3bb 100644
--- a/src/V3PreProc.cpp
+++ b/src/V3PreProc.cpp
@@ -299,11 +299,11 @@ void V3PreProcImp::undefineall() {
     }
 }
 bool V3PreProcImp::defExists(const string& name) {
-    DefinesMap::iterator iter = m_defines.find(name);
+    const auto iter = m_defines.find(name);
     return (iter != m_defines.end());
 }
 string V3PreProcImp::defValue(const string& name) {
-    DefinesMap::iterator iter = m_defines.find(name);
+    const auto iter = m_defines.find(name);
     if (iter == m_defines.end()) {
         fileline()->v3error("Define or directive not defined: `" + name);
         return "";
@@ -311,7 +311,7 @@ string V3PreProcImp::defValue(const string& name) {
     return iter->second.value();
 }
 string V3PreProcImp::defParams(const string& name) {
-    DefinesMap::iterator iter = m_defines.find(name);
+    const auto iter = m_defines.find(name);
     if (iter == m_defines.end()) {
         fileline()->v3error("Define or directive not defined: `" + name);
         return "";
@@ -319,7 +319,7 @@ string V3PreProcImp::defParams(const string& name) {
     return iter->second.params();
 }
 FileLine* V3PreProcImp::defFileline(const string& name) {
-    DefinesMap::iterator iter = m_defines.find(name);
+    const auto iter = m_defines.find(name);
     if (iter == m_defines.end()) return nullptr;
     return iter->second.fileline();
 }
@@ -686,7 +686,7 @@ string V3PreProcImp::defineSubst(VDefineRef* refp) {
             }
             if (argName != "") {
                 // Found a possible variable substitution
-                std::map<string, string>::iterator iter = argValueByName.find(argName);
+                const auto iter = argValueByName.find(argName);
                 if (iter != argValueByName.end()) {
                     // Substitute
                     string subst = iter->second;
@@ -795,9 +795,7 @@ void V3PreProcImp::openFile(FileLine* fl, VInFilter* filterp, const string& file
     FileLine* flsp = new FileLine(filename);
     flsp->lineno(1);
     flsp->newContent();
-    for (StrList::iterator it = wholefile.begin(); it != wholefile.end(); ++it) {
-        flsp->contentp()->pushText(*it);
-    }
+    for (const string& i : wholefile) flsp->contentp()->pushText(i);
 
     // Create new stream structure
     m_lexp->scanNewFile(flsp);
diff --git a/src/V3Reloop.cpp b/src/V3Reloop.cpp
index 1579d7e1e..eeb47b0c6 100644
--- a/src/V3Reloop.cpp
+++ b/src/V3Reloop.cpp
@@ -124,8 +124,7 @@ private:
                 if (debug() >= 9) whilep->dumpTree(cout, "-new: ");
 
                 // Remove remaining assigns
-                for (AssVec::iterator it = m_mgAssignps.begin(); it != m_mgAssignps.end(); ++it) {
-                    AstNodeAssign* assp = *it;
+                for (AstNodeAssign* assp : m_mgAssignps) {
                     if (assp != bodyp) {
                         VL_DO_DANGLING(assp->unlinkFrBack()->deleteTree(), assp);
                     }
diff --git a/src/V3Scope.cpp b/src/V3Scope.cpp
index 2e8207222..6b2f8518a 100644
--- a/src/V3Scope.cpp
+++ b/src/V3Scope.cpp
@@ -70,11 +70,11 @@ private:
             AstVarRef* nodep = it->first;
             AstScope* scopep = it->second;
             if (nodep->packagep() && !nodep->varp()->isClassMember()) {
-                PackageScopeMap::iterator it2 = m_packageScopes.find(nodep->packagep());
+                const auto it2 = m_packageScopes.find(nodep->packagep());
                 UASSERT_OBJ(it2 != m_packageScopes.end(), nodep, "Can't locate package scope");
                 scopep = it2->second;
             }
-            VarScopeMap::iterator it3 = m_varScopes.find(make_pair(nodep->varp(), scopep));
+            const auto it3 = m_varScopes.find(make_pair(nodep->varp(), scopep));
             UASSERT_OBJ(it3 != m_varScopes.end(), nodep, "Can't locate varref scope");
             AstVarScope* varscp = it3->second;
             nodep->varScopep(varscp);
diff --git a/src/V3Scoreboard.h b/src/V3Scoreboard.h
index f5933668d..beffd2ca7 100644
--- a/src/V3Scoreboard.h
+++ b/src/V3Scoreboard.h
@@ -247,16 +247,16 @@ private:
 
 public:
     iterator begin() {
-        typename Val2Keys::iterator valIt = m_vals.begin();
+        const auto valIt = m_vals.begin();
         if (valIt == m_vals.end()) return end();
-        typename KeySet::const_iterator keyIt = valIt->second.begin();
+        const auto keyIt = valIt->second.begin();
         return iterator(valIt, keyIt, this);
     }
     const_iterator begin() const {
         SortByValueMap* mutp = const_cast<SortByValueMap*>(this);
-        typename Val2Keys::iterator valIt = mutp->m_vals.begin();
+        const auto valIt = mutp->m_vals.begin();
         if (valIt == mutp->m_vals.end()) return end();
-        typename KeySet::const_iterator keyIt = valIt->second.begin();
+        const auto keyIt = valIt->second.begin();
         return const_iterator(valIt, keyIt, mutp);
     }
     iterator end() { return iterator(this); }
@@ -271,24 +271,24 @@ public:
     const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
 
     iterator find(const T_Key& k) {
-        typename Key2Val::iterator kvit = m_keys.find(k);
+        const auto kvit = m_keys.find(k);
         if (kvit == m_keys.end()) return end();
 
-        typename Val2Keys::iterator valIt = m_vals.find(kvit->second);
-        typename KeySet::iterator keyIt = valIt->second.find(k);
+        const auto valIt = m_vals.find(kvit->second);
+        const auto keyIt = valIt->second.find(k);
         return iterator(valIt, keyIt, this);
     }
     const_iterator find(const T_Key& k) const {
         SortByValueMap* mutp = const_cast<SortByValueMap*>(this);
-        typename Key2Val::iterator kvit = mutp->m_keys.find(k);
+        const auto kvit = mutp->m_keys.find(k);
         if (kvit == mutp->m_keys.end()) return end();
 
-        typename Val2Keys::iterator valIt = mutp->m_vals.find(kvit->second);
-        typename KeySet::iterator keyIt = valIt->second.find(k);
+        const auto valIt = mutp->m_vals.find(kvit->second);
+        const auto keyIt = valIt->second.find(k);
         return const_iterator(valIt, keyIt, mutp);
     }
     void set(const T_Key& k, const T_Value& v) {
-        typename Key2Val::iterator kvit = m_keys.find(k);
+        const auto kvit = m_keys.find(k);
         if (kvit != m_keys.end()) {
             if (kvit->second == v) {
                 return;  // LCOV_EXCL_LINE // Same value already present; stop.
@@ -300,7 +300,7 @@ public:
         m_vals[v].insert(k);
     }
     size_t erase(const T_Key& k) {
-        typename Key2Val::iterator kvit = m_keys.find(k);
+        const auto kvit = m_keys.find(k);
         if (kvit == m_keys.end()) return 0;
         removeKeyFromOldVal(k, kvit->second);
         m_keys.erase(kvit);
@@ -319,7 +319,7 @@ public:
     // be a const reference, otherwise the client could corrupt the sorted
     // order of m_byValue by reaching through and changing the value.
     const T_Value& at(const T_Key& k) const {
-        typename Key2Val::const_iterator kvit = m_keys.find(k);
+        const auto kvit = m_keys.find(k);
         UASSERT(kvit != m_keys.end(), "at() lookup key not found");
         return kvit->second;
     }
@@ -415,7 +415,7 @@ public:
     // reflected in the result of bestp(). Otherwise, bestp() only
     // considers elements that aren't pending rescore.
     const T_Elem* bestp() {
-        typename SortedMap::iterator result = m_sorted.begin();
+        const auto result = m_sorted.begin();
         if (VL_UNLIKELY(result == m_sorted.end())) return nullptr;
         return (*result).key();
     }
@@ -444,7 +444,7 @@ public:
     bool needsRescore(const T_Elem* elp) { return (m_unknown.find(elp) != m_unknown.end()); }
     // Retrieve the last known score for an element.
     T_Score cachedScore(const T_Elem* elp) {
-        typename SortedMap::iterator result = m_sorted.find(elp);
+        const auto result = m_sorted.find(elp);
         UASSERT(result != m_sorted.end(), "V3Scoreboard::cachedScore() failed to find element");
         return (*result).value();
     }
@@ -452,9 +452,7 @@ public:
     // call the client's scoring function to get a new score,
     // and sort all elements by their current score.
     void rescore() {
-        for (typename NeedRescoreSet::iterator it = m_unknown.begin(); it != m_unknown.end();
-             ++it) {
-            const T_Elem* elp = *it;
+        for (const T_Elem* elp : m_unknown) {
             T_Score sortScore = m_scoreFnp(elp);
             m_sorted.set(elp, sortScore);
         }
diff --git a/src/V3SenTree.h b/src/V3SenTree.h
index bfe49f5d8..806b5919f 100644
--- a/src/V3SenTree.h
+++ b/src/V3SenTree.h
@@ -60,7 +60,7 @@ public:
 
     AstSenTree* find(AstSenTree* likep) {
         AstSenTree* resultp = nullptr;
-        Set::iterator it = m_trees.find(likep);
+        const auto it = m_trees.find(likep);
         if (it != m_trees.end()) resultp = *it;
         return resultp;
     }
diff --git a/src/V3Simulate.h b/src/V3Simulate.h
index d8afa8e7c..dea714eca 100644
--- a/src/V3Simulate.h
+++ b/src/V3Simulate.h
@@ -1009,7 +1009,7 @@ private:
 
             string result;
             string format = nodep->text();
-            string::const_iterator pos = format.begin();
+            auto pos = format.cbegin();
             bool inPct = false;
             for (; pos != format.end(); ++pos) {
                 if (!inPct && pos[0] == '%') {
@@ -1132,15 +1132,10 @@ public:
         mainGuts(nodep);
     }
     virtual ~SimulateVisitor() override {
-        for (ConstPile::iterator it = m_constAllps.begin(); it != m_constAllps.end(); ++it) {
-            for (ConstDeque::iterator it2 = it->second.begin(); it2 != it->second.end(); ++it2) {
-                delete (*it2);
-            }
-        }
-        for (std::deque<AstNode*>::iterator it = m_reclaimValuesp.begin();
-             it != m_reclaimValuesp.end(); ++it) {
-            delete (*it);
+        for (const auto& i : m_constAllps) {
+            for (AstConst* i2p : i.second) delete i2p;
         }
+        for (AstNode* ip : m_reclaimValuesp) delete ip;
         m_reclaimValuesp.clear();
         m_constFreeps.clear();
         m_constAllps.clear();
diff --git a/src/V3Split.cpp b/src/V3Split.cpp
index 4fb8f7617..7828f66fd 100644
--- a/src/V3Split.cpp
+++ b/src/V3Split.cpp
@@ -394,18 +394,16 @@ protected:
                     SplitVarPostVertex* vpostp
                         = reinterpret_cast<SplitVarPostVertex*>(vscp->user2p());
                     // Add edges
-                    for (VStack::iterator it = m_stmtStackps.begin(); it != m_stmtStackps.end();
-                         ++it) {
-                        new SplitLVEdge(&m_graph, vpostp, *it);
+                    for (SplitLogicVertex* vxp : m_stmtStackps) {
+                        new SplitLVEdge(&m_graph, vpostp, vxp);
                     }
                 } else {  // Nondelayed assignment
                     if (nodep->lvalue()) {
                         // Non-delay; need to maintain existing ordering
                         // with all consumers of the signal
                         UINFO(4, "     VARREFLV: " << nodep << endl);
-                        for (VStack::iterator it = m_stmtStackps.begin();
-                             it != m_stmtStackps.end(); ++it) {
-                            new SplitLVEdge(&m_graph, vstdp, *it);
+                        for (SplitLogicVertex* ivxp : m_stmtStackps) {
+                            new SplitLVEdge(&m_graph, vstdp, ivxp);
                         }
                     } else {
                         UINFO(4, "     VARREF:   " << nodep << endl);
@@ -450,9 +448,7 @@ public:
     // METHODS
 protected:
     virtual void makeRvalueEdges(SplitVarStdVertex* vstdp) override {
-        for (VStack::iterator it = m_stmtStackps.begin(); it != m_stmtStackps.end(); ++it) {
-            new SplitRVEdge(&m_graph, *it, vstdp);
-        }
+        for (SplitLogicVertex* vxp : m_stmtStackps) new SplitRVEdge(&m_graph, vxp, vstdp);
     }
 
     void cleanupBlockGraph(AstNode* nodep) {
@@ -647,7 +643,7 @@ public:
     // METHODS
     const ColorSet& colors() const { return m_colors; }
     const ColorSet& colors(AstNodeIf* nodep) const {
-        IfColorMap::const_iterator it = m_ifColors.find(nodep);
+        const auto it = m_ifColors.find(nodep);
         UASSERT_OBJ(it != m_ifColors.end(), nodep, "Node missing from split color() map");
         return it->second;
     }
diff --git a/src/V3SplitVar.cpp b/src/V3SplitVar.cpp
index ad9bda871..71f54cb0b 100644
--- a/src/V3SplitVar.cpp
+++ b/src/V3SplitVar.cpp
@@ -981,7 +981,7 @@ class SplitPackedVarVisitor : public AstNVisitor, public SplitVarImpl {
     virtual void visit(AstVarRef* nodep) override {
         AstVar* varp = nodep->varp();
         visit(varp);
-        PackedVarRefMap::iterator refit = m_refs.find(varp);
+        const auto refit = m_refs.find(varp);
         if (refit == m_refs.end()) return;  // variable without split_var metacomment
         UASSERT_OBJ(varp->attrSplitVar(), varp, "split_var attribute must be attached");
         UASSERT_OBJ(!nodep->packagep(), nodep,
@@ -1000,7 +1000,7 @@ class SplitPackedVarVisitor : public AstNVisitor, public SplitVarImpl {
         }
 
         AstVar* varp = vrefp->varp();
-        PackedVarRefMap::iterator refit = m_refs.find(varp);
+        const auto refit = m_refs.find(varp);
         if (refit == m_refs.end()) {
             iterateChildren(nodep);
             return;  // Variable without split_var metacomment
@@ -1114,13 +1114,12 @@ class SplitPackedVarVisitor : public AstNVisitor, public SplitVarImpl {
     }
     static void updateReferences(AstVar* varp, PackedVarRef& ref,
                                  const std::vector<SplitNewVar>& vars) {
-        typedef std::vector<SplitNewVar> NewVars;  // Sorted by its lsb
         for (int lvalue = 0; lvalue <= 1; ++lvalue) {  // Refer the new split variables
             std::vector<PackedVarRefEntry>& refs = lvalue ? ref.lhs() : ref.rhs();
             for (PackedVarRef::iterator refit = refs.begin(), refitend = refs.end();
                  refit != refitend; ++refit) {
-                NewVars::const_iterator varit = std::upper_bound(
-                    vars.begin(), vars.end(), refit->lsb(), SplitNewVar::Match());
+                auto varit = std::upper_bound(vars.begin(), vars.end(), refit->lsb(),
+                                              SplitNewVar::Match());
                 UASSERT_OBJ(varit != vars.end(), refit->nodep(), "Not found");
                 UASSERT(!(varit->msb() < refit->lsb() || refit->msb() < varit->lsb()),
                         "wrong search result");
diff --git a/src/V3String.cpp b/src/V3String.cpp
index d2ea0f128..b9595c712 100644
--- a/src/V3String.cpp
+++ b/src/V3String.cpp
@@ -74,13 +74,13 @@ string VString::dot(const string& a, const string& dot, const string& b) {
 
 string VString::downcase(const string& str) {
     string out = str;
-    for (string::iterator pos = out.begin(); pos != out.end(); ++pos) *pos = tolower(*pos);
+    for (auto& cr : out) cr = tolower(cr);
     return out;
 }
 
 string VString::upcase(const string& str) {
     string out = str;
-    for (string::iterator pos = out.begin(); pos != out.end(); ++pos) *pos = toupper(*pos);
+    for (auto& cr : out) cr = toupper(cr);
     return out;
 }
 
diff --git a/src/V3Subst.cpp b/src/V3Subst.cpp
index ff857052a..fea0122de 100644
--- a/src/V3Subst.cpp
+++ b/src/V3Subst.cpp
@@ -372,10 +372,9 @@ public:
     }
     virtual ~SubstVisitor() override {
         V3Stats::addStat("Optimizations, Substituted temps", m_statSubsts);
-        for (std::vector<SubstVarEntry*>::iterator it = m_entryps.begin(); it != m_entryps.end();
-             ++it) {
-            (*it)->deleteUnusedAssign();
-            delete (*it);
+        for (SubstVarEntry* ip : m_entryps) {
+            ip->deleteUnusedAssign();
+            delete ip;
         }
     }
 };
diff --git a/src/V3SymTable.h b/src/V3SymTable.h
index f29ad4f14..d72925dbe 100644
--- a/src/V3SymTable.h
+++ b/src/V3SymTable.h
@@ -133,7 +133,7 @@ public:
         }
     }
     void reinsert(const string& name, VSymEnt* entp) {
-        IdNameMap::iterator it = m_idNameMap.find(name);
+        const auto it = m_idNameMap.find(name);
         if (name != "" && it != m_idNameMap.end()) {
             UINFO(9, "     SymReinsert se" << cvtToHex(this) << " '" << name << "' se"
                                            << cvtToHex(entp) << "  " << entp->nodep() << endl);
@@ -145,7 +145,7 @@ public:
     VSymEnt* findIdFlat(const string& name) const {
         // Find identifier without looking upward through symbol hierarchy
         // First, scan this begin/end block or module for the name
-        IdNameMap::const_iterator it = m_idNameMap.find(name);
+        const auto it = m_idNameMap.find(name);
         UINFO(9, "     SymFind   se"
                      << cvtToHex(this) << " '" << name << "' -> "
                      << (it == m_idNameMap.end()
@@ -211,7 +211,7 @@ public:
     void importFromPackage(VSymGraph* graphp, const VSymEnt* srcp, const string& id_or_star) {
         // Import tokens from source symbol table into this symbol table
         if (id_or_star != "*") {
-            IdNameMap::const_iterator it = srcp->m_idNameMap.find(id_or_star);
+            const auto it = srcp->m_idNameMap.find(id_or_star);
             if (it != srcp->m_idNameMap.end()) {
                 importOneSymbol(graphp, it->first, it->second, true);
             }
@@ -225,7 +225,7 @@ public:
     void exportFromPackage(VSymGraph* graphp, const VSymEnt* srcp, const string& id_or_star) {
         // Export tokens from source symbol table into this symbol table
         if (id_or_star != "*") {
-            IdNameMap::const_iterator it = srcp->m_idNameMap.find(id_or_star);
+            const auto it = vlstd::as_const(srcp->m_idNameMap).find(id_or_star);
             if (it != srcp->m_idNameMap.end()) exportOneSymbol(graphp, it->first, it->second);
         } else {
             for (IdNameMap::const_iterator it = srcp->m_idNameMap.begin();
@@ -292,7 +292,7 @@ class VSymGraph {
 public:
     explicit VSymGraph(AstNetlist* nodep) { m_symRootp = new VSymEnt(this, nodep); }
     ~VSymGraph() {
-        for (SymStack::iterator it = m_symsp.begin(); it != m_symsp.end(); ++it) delete (*it);
+        for (const VSymEnt* entp : m_symsp) delete entp;
     }
 
     // METHODS
diff --git a/src/V3TSP.cpp b/src/V3TSP.cpp
index 4cc49c3f9..4b7bd469f 100644
--- a/src/V3TSP.cpp
+++ b/src/V3TSP.cpp
@@ -84,7 +84,7 @@ public:
 
     // METHODS
     void addVertex(const T_Key& key) {
-        typename VMap::iterator itr = m_vertices.find(key);
+        const auto itr = m_vertices.find(key);
         UASSERT(itr == m_vertices.end(), "Vertex already exists with same key");
         Vertex* v = new Vertex(this, key);
         m_vertices[key] = v;
@@ -177,7 +177,7 @@ public:
         // discard it and repeat again.
         unsigned edges_made = 0;
         while (!pendingEdges.empty()) {
-            typename PendingEdgeSet::iterator firstIt = pendingEdges.begin();
+            const auto firstIt = pendingEdges.cbegin();
             V3GraphEdge* bestEdgep = *firstIt;
             pendingEdges.erase(firstIt);
 
@@ -317,8 +317,7 @@ public:
 
         // Look for nodes on the tour that still have
         // un-marked edges. If we find one, recurse.
-        for (typename std::vector<Vertex*>::iterator it = tour.begin(); it != tour.end(); ++it) {
-            Vertex* vxp = *it;
+        for (Vertex* vxp : tour) {
             bool recursed;
             do {
                 recursed = false;
@@ -338,10 +337,7 @@ public:
         }
 
         UINFO(6, "Tour was: ");
-        for (typename std::vector<Vertex*>::iterator it = tour.begin(); it != tour.end(); ++it) {
-            Vertex* vxp = *it;
-            UINFONL(6, " " << vxp->key());
-        }
+        for (const Vertex* vxp : tour) UINFONL(6, " " << vxp->key());
         UINFONL(6, "\n");
     }
 
@@ -390,7 +386,7 @@ public:
 
 private:
     Vertex* findVertex(const T_Key& key) const {
-        typename VMap::const_iterator it = m_vertices.find(key);
+        const auto it = m_vertices.find(key);
         UASSERT(it != m_vertices.end(), "Vertex not found");
         return it->second;
     }
diff --git a/src/V3Table.cpp b/src/V3Table.cpp
index 629542549..988a6058d 100644
--- a/src/V3Table.cpp
+++ b/src/V3Table.cpp
@@ -224,16 +224,14 @@ private:
         // Create table for each output
         typedef std::map<string, int> NameCounts;
         NameCounts namecounts;
-        for (std::deque<AstVarScope*>::iterator it = m_outVarps.begin(); it != m_outVarps.end();
-             ++it) {
-            AstVarScope* outvscp = *it;
+        for (const AstVarScope* outvscp : m_outVarps) {
             AstVar* outvarp = outvscp->varp();
             FileLine* fl = nodep->fileline();
             AstNodeArrayDType* dtypep = new AstUnpackArrayDType(
                 fl, outvarp->dtypep(), new AstRange(fl, VL_MASK_I(m_inWidth), 0));
             v3Global.rootp()->typeTablep()->addTypesp(dtypep);
             string name = "__Vtable" + cvtToStr(m_modTables) + "_" + outvarp->name();
-            NameCounts::iterator nit = namecounts.find(name);
+            const auto nit = namecounts.find(name);
             if (nit != namecounts.end()) {
                 // Multiple scopes can have same var name. We could append the
                 // scope name but that is very long, so just deduplicate.
@@ -256,9 +254,7 @@ private:
         // Concat inputs into a single temp variable (inside always)
         // First var in inVars becomes the LSB of the concat
         AstNode* concatp = nullptr;
-        for (std::deque<AstVarScope*>::iterator it = m_inVarps.begin(); it != m_inVarps.end();
-             ++it) {
-            AstVarScope* invscp = *it;
+        for (AstVarScope* invscp : m_inVarps) {
             AstVarRef* refp = new AstVarRef(nodep->fileline(), invscp, false);
             if (concatp) {
                 concatp = new AstConcat(nodep->fileline(), refp, concatp);
@@ -293,9 +289,7 @@ private:
 
             // Set all inputs to the constant
             uint32_t shift = 0;
-            for (std::deque<AstVarScope*>::iterator it = m_inVarps.begin(); it != m_inVarps.end();
-                 ++it) {
-                AstVarScope* invscp = *it;
+            for (AstVarScope* invscp : m_inVarps) {
                 // LSB is first variable, so extract it that way
                 AstConst cnst(invscp->fileline(), AstConst::WidthedValue(), invscp->width(),
                               VL_MASK_I(invscp->width()) & (inValue >> shift));
@@ -316,9 +310,7 @@ private:
             // If a output changed, add it to table
             int outnum = 0;
             V3Number outputChgMask(nodep, m_outVarps.size(), 0);
-            for (std::deque<AstVarScope*>::iterator it = m_outVarps.begin();
-                 it != m_outVarps.end(); ++it) {
-                AstVarScope* outvscp = *it;
+            for (AstVarScope* outvscp : m_outVarps) {
                 V3Number* outnump = simvis.fetchOutNumberNull(outvscp);
                 AstNode* setp;
                 if (!outnump) {
@@ -353,9 +345,7 @@ private:
         // See if another table we've created is identical, if so use it for both.
         // (A more 'modern' way would be to instead use V3Hashed::findDuplicate)
         AstVar* var1p = vsc1p->varp();
-        for (std::deque<AstVarScope*>::iterator it = m_modTableVscs.begin();
-             it != m_modTableVscs.end(); ++it) {
-            AstVarScope* vsc2p = *it;
+        for (AstVarScope* vsc2p : m_modTableVscs) {
             AstVar* var2p = vsc2p->varp();
             if (var1p->width() == var2p->width()
                 && (var1p->dtypep()->arrayUnpackedElements()
@@ -381,9 +371,7 @@ private:
         // elimination will remove it for us.
         // Set each output from array ref into our table
         int outnum = 0;
-        for (std::deque<AstVarScope*>::iterator it = m_outVarps.begin(); it != m_outVarps.end();
-             ++it) {
-            AstVarScope* outvscp = *it;
+        for (AstVarScope* outvscp : m_outVarps) {
             AstNode* alhsp = new AstVarRef(nodep->fileline(), outvscp, true);
             AstNode* arhsp = new AstArraySel(
                 nodep->fileline(), new AstVarRef(nodep->fileline(), m_tableVarps[outnum], false),
diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index b34dd4ed3..0708e0cdb 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -121,7 +121,7 @@ public:
         return scopep;
     }
     AstVarScope* findVarScope(AstScope* scopep, AstVar* nodep) {
-        VarToScopeMap::iterator iter = m_varToScopeMap.find(make_pair(scopep, nodep));
+        const auto iter = m_varToScopeMap.find(make_pair(scopep, nodep));
         UASSERT_OBJ(iter != m_varToScopeMap.end(), nodep, "No scope for var");
         return iter->second;
     }
@@ -233,8 +233,7 @@ private:
             iterateChildren(nodep);
         }
         UASSERT_OBJ(m_ctorp, nodep, "class constructor missing");  // LinkDot always makes it
-        for (Initials::iterator it = m_initialps.begin(); it != m_initialps.end(); ++it) {
-            AstInitial* initialp = *it;
+        for (AstInitial* initialp : m_initialps) {
             if (AstNode* newp = initialp->bodysp()) {
                 newp->unlinkFrBackWithNext();
                 if (!m_ctorp->stmtsp()) {
@@ -812,7 +811,7 @@ private:
     bool duplicatedDpiProto(AstNodeFTask* nodep, const string& dpiproto) {
         // Only create one DPI extern prototype for each specified cname
         // as it's legal for the user to attach multiple tasks to one dpi cname
-        DpiNames::iterator iter = m_dpiNames.find(nodep->cname());
+        const auto iter = m_dpiNames.find(nodep->cname());
         if (iter == m_dpiNames.end()) {
             m_dpiNames.insert(make_pair(nodep->cname(), make_pair(nodep, dpiproto)));
             return false;
@@ -1401,7 +1400,7 @@ V3TaskConnects V3Task::taskConnects(AstNodeFTaskRef* nodep, AstNode* taskStmtsp)
         UASSERT_OBJ(argp, pinp, "Non-arg under ftask reference");
         if (argp->name() != "") {
             // By name
-            NameToIndex::iterator it = nameToIndex.find(argp->name());
+            const auto it = nameToIndex.find(argp->name());
             if (it == nameToIndex.end()) {
                 pinp->v3error("No such argument " << argp->prettyNameQ() << " in function call to "
                                                   << nodep->taskp()->prettyTypeName());
diff --git a/src/V3Trace.cpp b/src/V3Trace.cpp
index db9f3ebc6..cb29a734e 100644
--- a/src/V3Trace.cpp
+++ b/src/V3Trace.cpp
@@ -220,7 +220,7 @@ private:
             if (TraceTraceVertex* const vvertexp = dynamic_cast<TraceTraceVertex*>(itp)) {
                 AstTraceDecl* const nodep = vvertexp->nodep();
                 if (nodep->valuep() && !vvertexp->duplicatep()) {
-                    V3Hashed::iterator dupit = hashed.findDuplicate(nodep->valuep());
+                    const auto dupit = hashed.findDuplicate(nodep->valuep());
                     if (dupit != hashed.end()) {
                         const AstTraceDecl* const dupDeclp
                             = VN_CAST_CONST(hashed.iteratorNodep(dupit)->backp(), TraceDecl);
@@ -381,10 +381,10 @@ private:
         // For each activity set with only a small number of signals, make those
         // signals always traced, as it's cheaper to check a few value changes
         // than to test a lot of activity flags
-        TraceVec::iterator it = traces.begin();
-        const TraceVec::iterator end = traces.end();
+        auto it = traces.begin();
+        const auto end = traces.end();
         while (it != end) {
-            TraceVec::iterator head = it;
+            auto head = it;
             // Approximate the complexity of the value change check
             uint32_t complexity = 0;
             const ActCodeSet& actSet = it->first;
@@ -533,8 +533,8 @@ private:
 
         int topFuncNum = 0;
         int subFuncNum = 0;
-        TraceVec::const_iterator it = traces.begin();
-        while (it != traces.end()) {
+        auto it = traces.cbegin();
+        while (it != traces.cend()) {
             AstCFunc* topFuncp = nullptr;
             AstCFunc* subFuncp = nullptr;
             int subStmts = 0;
@@ -637,8 +637,7 @@ private:
                     if (always) {
                         condp = new AstConst(flp, 1);  // Always true, will be folded later
                     } else {
-                        for (ActCodeSet::iterator it = actSet.begin(); it != actSet.end(); ++it) {
-                            const uint32_t actCode = *it;
+                        for (const uint32_t actCode : actSet) {
                             AstNode* const selp = selectActivity(flp, actCode, false);
                             condp = condp ? new AstOr(flp, condp, selp) : selp;
                         }
diff --git a/src/V3Tristate.cpp b/src/V3Tristate.cpp
index 7b16dcb19..657de4ceb 100644
--- a/src/V3Tristate.cpp
+++ b/src/V3Tristate.cpp
@@ -421,7 +421,7 @@ class TristateVisitor : public TristateBaseVisitor {
 
     void mapInsertLhsVarRef(AstVarRef* nodep) {
         AstVar* key = nodep->varp();
-        VarMap::iterator it = m_lhsmap.find(key);
+        const auto it = m_lhsmap.find(key);
         UINFO(9, "    mapInsertLhsVarRef " << nodep << endl);
         if (it == m_lhsmap.end()) {  // Not found
             RefVec* refsp = new RefVec();
@@ -482,7 +482,7 @@ class TristateVisitor : public TristateBaseVisitor {
         for (TristateGraph::VarVec::iterator ii = vars.begin(); ii != vars.end(); ++ii) {
             AstVar* varp = (*ii);
             if (m_tgraph.isTristate(varp)) {
-                VarMap::iterator it = m_lhsmap.find(varp);
+                const auto it = m_lhsmap.find(varp);
                 if (it == m_lhsmap.end()) {
                     // set output enable to always be off on this assign
                     // statement so that this var is floating
diff --git a/src/V3Undriven.cpp b/src/V3Undriven.cpp
index 165801528..f8fb7b978 100644
--- a/src/V3Undriven.cpp
+++ b/src/V3Undriven.cpp
@@ -441,15 +441,9 @@ public:
     // CONSTRUCTORS
     explicit UndrivenVisitor(AstNetlist* nodep) { iterate(nodep); }
     virtual ~UndrivenVisitor() override {
-        for (std::vector<UndrivenVarEntry*>::iterator it = m_entryps[1].begin();
-             it != m_entryps[1].end(); ++it) {
-            (*it)->reportViolations();
-        }
+        for (UndrivenVarEntry* ip : m_entryps[1]) ip->reportViolations();
         for (int usr = 1; usr < 3; ++usr) {
-            for (std::vector<UndrivenVarEntry*>::iterator it = m_entryps[usr].begin();
-                 it != m_entryps[usr].end(); ++it) {
-                delete (*it);
-            }
+            for (UndrivenVarEntry* ip : m_entryps[usr]) delete ip;
         }
     }
 };
diff --git a/src/V3Width.cpp b/src/V3Width.cpp
index 8522e91ca..ac878bfd7 100644
--- a/src/V3Width.cpp
+++ b/src/V3Width.cpp
@@ -2876,7 +2876,7 @@ private:
         AstNode* newp = nullptr;
         for (AstMemberDType* memp = vdtypep->membersp(); memp;
              memp = VN_CAST(memp->nextp(), MemberDType)) {
-            PatMap::iterator it = patmap.find(memp);
+            const auto it = patmap.find(memp);
             AstPatMember* newpatp = nullptr;
             AstPatMember* patp = nullptr;
             if (it == patmap.end()) {
@@ -2923,7 +2923,7 @@ private:
         for (int ent = range.hi(); ent >= range.lo(); --ent) {
             AstPatMember* newpatp = nullptr;
             AstPatMember* patp = nullptr;
-            PatVecMap::iterator it = patmap.find(ent);
+            const auto it = patmap.find(ent);
             if (it == patmap.end()) {
                 if (defaultp) {
                     newpatp = defaultp->cloneTree(false);
@@ -2978,7 +2978,7 @@ private:
         for (int ent = range.hi(); ent >= range.lo(); --ent) {
             AstPatMember* newpatp = nullptr;
             AstPatMember* patp = nullptr;
-            PatVecMap::iterator it = patmap.find(ent);
+            const auto it = patmap.find(ent);
             if (it == patmap.end()) {
                 if (defaultp) {
                     newpatp = defaultp->cloneTree(false);
@@ -5158,7 +5158,7 @@ private:
     }
     AstVar* dimensionVarp(AstNodeDType* nodep, AstAttrType attrType, uint32_t msbdim) {
         // Return a variable table which has specified dimension properties for this variable
-        TableMap::iterator pos = m_tableMap.find(make_pair(nodep, attrType));
+        const auto pos = m_tableMap.find(make_pair(nodep, attrType));
         if (pos != m_tableMap.end()) return pos->second;
         AstNodeArrayDType* vardtypep
             = new AstUnpackArrayDType(nodep->fileline(), nodep->findSigned32DType(),
@@ -5185,7 +5185,7 @@ private:
     }
     AstVar* enumVarp(AstEnumDType* nodep, AstAttrType attrType, uint32_t msbdim) {
         // Return a variable table which has specified dimension properties for this variable
-        TableMap::iterator pos = m_tableMap.find(make_pair(nodep, attrType));
+        const auto pos = m_tableMap.find(make_pair(nodep, attrType));
         if (pos != m_tableMap.end()) return pos->second;
         UINFO(9, "Construct Venumtab attr=" << attrType.ascii() << " max=" << msbdim << " for "
                                             << nodep << endl);
diff --git a/src/VlcMain.cpp b/src/VlcMain.cpp
index c004e8efc..6375c2a09 100644
--- a/src/VlcMain.cpp
+++ b/src/VlcMain.cpp
@@ -154,10 +154,7 @@ int main(int argc, char** argv, char** /*env*/) {
 
     {
         const VlStringSet& readFiles = top.opt.readFiles();
-        for (VlStringSet::const_iterator it = readFiles.begin(); it != readFiles.end(); ++it) {
-            string filename = *it;
-            top.readCoverage(filename);
-        }
+        for (const auto& filename : readFiles) top.readCoverage(filename);
     }
 
     if (debug() >= 9) {
@@ -179,10 +176,7 @@ int main(int argc, char** argv, char** /*env*/) {
         V3Error::abortIfWarnings();
         if (top.opt.unlink()) {
             const VlStringSet& readFiles = top.opt.readFiles();
-            for (VlStringSet::const_iterator it = readFiles.begin(); it != readFiles.end(); ++it) {
-                string filename = *it;
-                unlink(filename.c_str());
-            }
+            for (const auto& filename : readFiles) { unlink(filename.c_str()); }
         }
     }
 
diff --git a/src/VlcPoint.h b/src/VlcPoint.h
index 2b37c58e6..83eefd85d 100644
--- a/src/VlcPoint.h
+++ b/src/VlcPoint.h
@@ -113,15 +113,15 @@ public:
     void dump() {
         UINFO(2, "dumpPoints...\n");
         VlcPoint::dumpHeader();
-        for (VlcPoints::ByName::const_iterator it = begin(); it != end(); ++it) {
-            const VlcPoint& point = pointNumber(it->second);
+        for (const auto& i : *this) {
+            const VlcPoint& point = pointNumber(i.second);
             point.dump();
         }
     }
     VlcPoint& pointNumber(vluint64_t num) { return m_points[num]; }
     vluint64_t findAddPoint(const string& name, vluint64_t count) {
         vluint64_t pointnum;
-        NameMap::const_iterator iter = m_nameMap.find(name);
+        const auto iter = m_nameMap.find(name);
         if (iter != m_nameMap.end()) {
             pointnum = iter->second;
             m_points[pointnum].countInc(count);
diff --git a/src/VlcTest.h b/src/VlcTest.h
index f95bd4de6..d1489e661 100644
--- a/src/VlcTest.h
+++ b/src/VlcTest.h
@@ -102,18 +102,14 @@ public:
     // CONSTRUCTORS
     VlcTests() {}
     ~VlcTests() {
-        for (VlcTests::ByName::iterator it = begin(); it != end(); ++it) {
-            VL_DO_CLEAR(delete *it, *it = nullptr);
-        }
+        for (auto it = begin(); it != end(); ++it) { VL_DO_CLEAR(delete *it, *it = nullptr); }
     }
 
     // METHODS
     void dump(bool bucketsToo) {
         UINFO(2, "dumpTests...\n");
         VlcTest::dumpHeader();
-        for (VlcTests::ByName::const_iterator it = begin(); it != end(); ++it) {
-            (*it)->dump(bucketsToo);
-        }
+        for (const auto& testp : m_tests) testp->dump(bucketsToo);
     }
     VlcTest* newTest(const string& name, vluint64_t testrun, double comp) {
         VlcTest* testp = new VlcTest(name, testrun, comp);
@@ -121,7 +117,7 @@ public:
         return testp;
     }
     void clearUser() {
-        for (ByName::iterator it = m_tests.begin(); it != m_tests.end(); ++it) (*it)->user(0);
+        for (const auto& testp : m_tests) testp->user(0);
     }
 };
 
diff --git a/src/VlcTop.cpp b/src/VlcTop.cpp
index 9e5ddd260..4ff050d5f 100644
--- a/src/VlcTop.cpp
+++ b/src/VlcTop.cpp
@@ -70,8 +70,8 @@ void VlcTop::writeCoverage(const string& filename) {
     }
 
     os << "# SystemC::Coverage-3" << endl;
-    for (VlcPoints::ByName::const_iterator it = m_points.begin(); it != m_points.end(); ++it) {
-        const VlcPoint& point = m_points.pointNumber(it->second);
+    for (const auto& i : m_points) {
+        const VlcPoint& point = m_points.pointNumber(i.second);
         os << "C '" << point.name() << "' " << point.count() << endl;
     }
 }
@@ -107,17 +107,17 @@ void VlcTop::writeInfo(const string& filename) {
     //   end_of_record
 
     os << "TN:verilator_coverage\n";
-    for (VlcSources::NameMap::iterator sit = m_sources.begin(); sit != m_sources.end(); ++sit) {
-        VlcSource& source = sit->second;
+    for (auto& si : m_sources) {
+        VlcSource& source = si.second;
         os << "SF:" << source.name() << endl;
         VlcSource::LinenoMap& lines = source.lines();
-        for (VlcSource::LinenoMap::iterator lit = lines.begin(); lit != lines.end(); ++lit) {
-            int lineno = lit->first;
-            VlcSource::ColumnMap& cmap = lit->second;
+        for (auto& li : lines) {
+            int lineno = li.first;
+            VlcSource::ColumnMap& cmap = li.second;
             bool first = true;
             vluint64_t min_count = 0;  // Minimum across all columns on line
-            for (VlcSource::ColumnMap::iterator cit = cmap.begin(); cit != cmap.end(); ++cit) {
-                VlcSourceCount& col = cit->second;
+            for (auto& ci : cmap) {
+                VlcSourceCount& col = ci.second;
                 if (first) {
                     min_count = col.count();
                     first = false;
@@ -148,17 +148,16 @@ void VlcTop::rank() {
 
     // Sort by computrons, so fast tests get selected first
     std::vector<VlcTest*> bytime;
-    for (VlcTests::ByName::const_iterator it = m_tests.begin(); it != m_tests.end(); ++it) {
-        VlcTest* testp = *it;
+    for (const auto& testp : m_tests) {
         if (testp->bucketsCovered()) {  // else no points, so can't help us
-            bytime.push_back(*it);
+            bytime.push_back(testp);
         }
     }
     sort(bytime.begin(), bytime.end(), CmpComputrons());  // Sort the vector
 
     VlcBuckets remaining;
-    for (VlcPoints::ByName::const_iterator it = m_points.begin(); it != m_points.end(); ++it) {
-        VlcPoint* pointp = &points().pointNumber(it->second);
+    for (const auto& i : m_points) {
+        VlcPoint* pointp = &points().pointNumber(i.second);
         // If any tests hit this point, then we'll need to cover it.
         if (pointp->testsCovering()) remaining.addData(pointp->pointNum(), 1);
     }
@@ -174,8 +173,7 @@ void VlcTop::rank() {
         }
         VlcTest* bestTestp = nullptr;
         vluint64_t bestRemain = 0;
-        for (std::vector<VlcTest*>::iterator it = bytime.begin(); it != bytime.end(); ++it) {
-            VlcTest* testp = *it;
+        for (const auto& testp : bytime) {
             if (!testp->rank()) {
                 vluint64_t remain = testp->buckets().dataPopCount(remaining);
                 if (remain > bestRemain) {
@@ -198,8 +196,8 @@ void VlcTop::rank() {
 
 void VlcTop::annotateCalc() {
     // Calculate per-line information into filedata structure
-    for (VlcPoints::ByName::const_iterator it = m_points.begin(); it != m_points.end(); ++it) {
-        const VlcPoint& point = m_points.pointNumber(it->second);
+    for (const auto& i : m_points) {
+        const VlcPoint& point = m_points.pointNumber(i.second);
         string filename = point.filename();
         int lineno = point.lineno();
         if (!filename.empty() && lineno != 0) {
@@ -244,15 +242,15 @@ void VlcTop::annotateCalcNeeded() {
     // coverage in all categories
     int totCases = 0;
     int totOk = 0;
-    for (VlcSources::NameMap::iterator sit = m_sources.begin(); sit != m_sources.end(); ++sit) {
-        VlcSource& source = sit->second;
+    for (auto& si : m_sources) {
+        VlcSource& source = si.second;
         // UINFO(1,"Source "<<source.name()<<endl);
         if (opt.annotateAll()) source.needed(true);
         VlcSource::LinenoMap& lines = source.lines();
-        for (VlcSource::LinenoMap::iterator lit = lines.begin(); lit != lines.end(); ++lit) {
-            VlcSource::ColumnMap& cmap = lit->second;
-            for (VlcSource::ColumnMap::iterator cit = cmap.begin(); cit != cmap.end(); ++cit) {
-                VlcSourceCount& col = cit->second;
+        for (auto& li : lines) {
+            VlcSource::ColumnMap& cmap = li.second;
+            for (auto& ci : cmap) {
+                VlcSourceCount& col = ci.second;
                 // UINFO(0,"Source "<<source.name()<<":"<<col.lineno()<<":"<<col.column()<<endl);
                 ++totCases;
                 if (col.ok()) {
@@ -272,8 +270,8 @@ void VlcTop::annotateCalcNeeded() {
 void VlcTop::annotateOutputFiles(const string& dirname) {
     // Create if uncreated, ignore errors
     V3Os::createDir(dirname);
-    for (VlcSources::NameMap::iterator sit = m_sources.begin(); sit != m_sources.end(); ++sit) {
-        VlcSource& source = sit->second;
+    for (auto& si : m_sources) {
+        VlcSource& source = si.second;
         if (!source.needed()) continue;
         string filename = source.name();
         string outfilename = dirname + "/" + V3Os::filenameNonDir(filename);
@@ -302,11 +300,11 @@ void VlcTop::annotateOutputFiles(const string& dirname) {
             bool first = true;
 
             VlcSource::LinenoMap& lines = source.lines();
-            VlcSource::LinenoMap::iterator lit = lines.find(lineno);
+            const auto lit = lines.find(lineno);
             if (lit != lines.end()) {
                 VlcSource::ColumnMap& cmap = lit->second;
-                for (VlcSource::ColumnMap::iterator cit = cmap.begin(); cit != cmap.end(); ++cit) {
-                    VlcSourceCount& col = cit->second;
+                for (auto& ci : cmap) {
+                    VlcSourceCount& col = ci.second;
                     // UINFO(0,"Source
                     // "<<source.name()<<":"<<col.lineno()<<":"<<col.column()<<endl);
                     os << (col.ok() ? " " : "%") << std::setfill('0') << std::setw(6)
diff --git a/test_regress/t/t_scope_map.cpp b/test_regress/t/t_scope_map.cpp
index 082fa53bc..8f27bf268 100644
--- a/test_regress/t/t_scope_map.cpp
+++ b/test_regress/t/t_scope_map.cpp
@@ -48,19 +48,18 @@ int main(int argc, char** argv, char** env) {
             return -1;
         }
 
-        for (VerilatedVarNameMap::iterator varIt = varNameMap->begin(); varIt != varNameMap->end();
-             ++varIt) {
-            VerilatedVar* var = &varIt->second;
-            int varLeft = var->packed().left();
-            int varRight = var->packed().right();
+        for (const auto& varname : *varNameMap) {
+            const VerilatedVar* varp = &(varname.second);
+            int varLeft = varp->packed().left();
+            int varRight = varp->packed().right();
 
 #ifdef TEST_VERBOSE
-            VL_PRINTF("\tVar = %s\n", varIt->first);
-            VL_PRINTF("\t  Type = %d\n", var->vltype());
-            VL_PRINTF("\t  EntSize = %d\n", var->entSize());
-            VL_PRINTF("\t  Dims = %d\n", var->dims());
+            VL_PRINTF("\tVar = %s\n", varname.first);
+            VL_PRINTF("\t  Type = %d\n", varp->vltype());
+            VL_PRINTF("\t  EntSize = %d\n", varp->entSize());
+            VL_PRINTF("\t  Dims = %d\n", varp->dims());
             VL_PRINTF("\t  Range = %d:%d\n", varLeft, varRight);
-            VL_PRINTF("\t  Is RW = %d\n", var->isPublicRW());
+            VL_PRINTF("\t  Is RW = %d\n", varp->isPublicRW());
 #endif
 
             if (varRight != 0) {
@@ -71,7 +70,7 @@ int main(int argc, char** argv, char** env) {
             int varBits = varLeft + 1;
 
             // First expect an incrementing byte pattern
-            vluint8_t* varData = reinterpret_cast<vluint8_t*>(var->datap());
+            vluint8_t* varData = reinterpret_cast<vluint8_t*>(varp->datap());
             for (int i = 0; i < varBits / 8; i++) {
 #ifdef TEST_VERBOSE
                 VL_PRINTF("%02x ", varData[i]);
@@ -124,19 +123,18 @@ int main(int argc, char** argv, char** env) {
             return -1;
         }
 
-        for (VerilatedVarNameMap::iterator varIt = varNameMap->begin(); varIt != varNameMap->end();
-             ++varIt) {
-            VerilatedVar* var = &varIt->second;
-            int varLeft = var->packed().left();
+        for (const auto& varname : *varNameMap) {
+            const VerilatedVar* varp = &(varname.second);
+            int varLeft = varp->packed().left();
             int varBits = varLeft + 1;
-            vluint8_t* varData = reinterpret_cast<vluint8_t*>(var->datap());
+            vluint8_t* varData = reinterpret_cast<vluint8_t*>(varp->datap());
 
             // Check that all bits are high now
             for (int i = 0; i < varBits / 8; i++) {
                 vluint8_t expected = 0xff;
                 if (varData[i] != expected) {
                     VL_PRINTF("%%Error: Data mismatch (%s), got 0x%02x, expected 0x%02x\n",
-                              varIt->first, varData[i], expected);
+                              varname.first, varData[i], expected);
                     return -1;
                 }
             }
@@ -146,7 +144,7 @@ int main(int argc, char** argv, char** env) {
                 vluint8_t expected = ~(0xff << (varBits % 8));
                 if (got != expected) {
                     VL_PRINTF("%%Error: Data mismatch (%s), got 0x%02x, expected 0x%02x\n",
-                              varIt->first, got, expected);
+                              varname.first, got, expected);
                     return -1;
                 }
             }