diff --git a/Module.cc b/Module.cc
index 75e1c0f8d..2602aee7a 100644
--- a/Module.cc
+++ b/Module.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1998-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -148,7 +148,7 @@ bool Module::can_be_toplevel() const
 
       // Don't choose modules with parameters without default value
       for (std::map<perm_string,param_expr_t*>::const_iterator cur =
-	    parameters.begin(); cur != parameters.end(); cur++) {
+	    parameters.begin(); cur != parameters.end(); ++cur) {
 	    if (cur->second->expr == 0)
 		  return false;
       }
diff --git a/cppcheck.sup b/cppcheck.sup
index 6b9d3c9b8..b7b2ede5d 100644
--- a/cppcheck.sup
+++ b/cppcheck.sup
@@ -1,20 +1,20 @@
 // These are correct and are used to find the base (zero) pin.
-thisSubtraction:netlist.h:5213
-thisSubtraction:netlist.h:5222
+thisSubtraction:netlist.h:5244
+thisSubtraction:netlist.h:5253
 
 // This is used when running a debugger
 // debugger_release
-knownConditionTrueFalse:main.cc:919
+knownConditionTrueFalse:main.cc:921
 
 // This are just stubs
 // vpi_control()
-unusedFunction:vpi_modules.cc:107
+unusedFunction:vpi_modules.cc:109
 // vpi_mcd_printf()
-unusedFunction:vpi_modules.cc:84
+unusedFunction:vpi_modules.cc:86
 // vpi_printf()
-unusedFunction:vpi_modules.cc:88
+unusedFunction:vpi_modules.cc:90
 // vpi_sim_control()
-unusedFunction:vpi_modules.cc:108
+unusedFunction:vpi_modules.cc:110
 
 // These are the functions that the compiler exports to the targets.
 //ivl_branch_island()
diff --git a/elab_expr.cc b/elab_expr.cc
index 6ee81e04f..af11c7559 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -2943,7 +2943,7 @@ unsigned PECallFunction::elaborate_arguments_(Design*des, NetScope*scope,
 
       for (unsigned idx = 0 ; idx < parm_count ; idx += 1) {
 	    unsigned pidx = idx + parm_off;
-	    PExpr*tmp = (idx < actual_count) ? parms_[idx] : 0;
+	    PExpr*tmp = (idx < actual_count) ? parms_[idx] : NULL;
 	    if (tmp) {
 		  parms[pidx] = elaborate_rval_expr(des, scope,
 						    def->port(pidx)->net_type(),
@@ -3177,7 +3177,7 @@ NetExpr* PECallFunction::elaborate_expr_method_(Design*des, NetScope*scope,
 	    // Get the method name that we are looking for.
 	    perm_string method_name = search_results.path_tail.back().name;
 
-	    PExpr*tmp = parms_.size() ? parms_[0] : 0;
+	    PExpr*tmp = parms_.size() ? parms_[0] : NULL;
 	    return check_for_enum_methods(this, des, scope,
 					  netenum, path_,
 					  method_name, sub_expr,
@@ -4171,7 +4171,7 @@ unsigned PEIdent::test_width(Design*des, NetScope*scope, width_mode_t&mode)
 	    ivl_assert(*this, 0);
       }
 
-      if (const netdarray_t*darray = sr.net ? sr.net->darray_type() : 0) {
+      if (const netdarray_t*darray = sr.net ? sr.net->darray_type() : NULL) {
 	    switch (use_sel) {
 		case index_component_t::SEL_BIT:
 		case index_component_t::SEL_BIT_LAST:
diff --git a/elab_lval.cc b/elab_lval.cc
index 3c8a82c69..3379b658e 100644
--- a/elab_lval.cc
+++ b/elab_lval.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2012-2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -183,7 +183,6 @@ NetAssign_* PEIdent::elaborate_lval(Design*des,
       symbol_search(this, des, use_scope, path_, &sr);
 
       NetNet *reg = sr.net;
-      pform_name_t &base_path = sr.path_head;
       pform_name_t &member_path = sr.path_tail;
 
 	/* The l-value must be a variable. If not, then give up and
@@ -221,6 +220,7 @@ NetAssign_* PEIdent::elaborate_lval(Design*des,
 	    else
 		  cerr << get_fileline() << ": " << __func__ << ": "
 		       << "reg->net_type()=<nil>" << endl;
+	    const pform_name_t &base_path = sr.path_head;
 	    cerr << get_fileline() << ": " << __func__ << ": "
 		 << " base_path=" << base_path
 		 << ", member_path=" << member_path
diff --git a/elab_net.cc b/elab_net.cc
index ae00cd093..2e45929a0 100644
--- a/elab_net.cc
+++ b/elab_net.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2012 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -1115,7 +1115,7 @@ NetNet*PEIdent::elaborate_unpacked_net(Design*des, NetScope*scope) const
       }
 
       const name_component_t&name_tail = path_.back();
-      if (name_tail.index.size() != 0) {
+      if (!name_tail.index.empty()) {
 	    cerr << get_fileline() << ": sorry: Array slices are not yet "
 	         << "supported for continuous assignment." << endl;
 	    des->errors += 1;
diff --git a/elab_scope.cc b/elab_scope.cc
index 41723b95d..b58c098fc 100644
--- a/elab_scope.cc
+++ b/elab_scope.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -415,7 +415,7 @@ static void blend_class_constructors(PClass*pclass)
 	// While we're here, look for a super.new() call. If we find
 	// it, strip it out of the constructor and set it aside for
 	// when we actually call the chained constructor.
-      PChainConstructor*chain_new = use_new? use_new->extract_chain_constructor() : 0;
+      PChainConstructor*chain_new = use_new? use_new->extract_chain_constructor() : NULL;
 
 	// If we do not have an explicit constructor chain, but there
 	// is a parent class, then create an implicit chain.
@@ -457,7 +457,6 @@ static void blend_class_constructors(PClass*pclass)
 	    } else {
 		  use_new->push_statement_front(chain_new);
 	    }
-	    chain_new = 0;
       }
 }
 
@@ -1153,7 +1152,6 @@ bool PGenerate::generate_scope_case_(Design*des, NetScope*container)
       }
 
       delete case_value_co;
-      case_value_co = 0;
 
       PGenerate*item = (cur == generate_schemes.end())? default_item : *cur;
       if (item == 0) {
diff --git a/elaborate.cc b/elaborate.cc
index 41ce06ca0..127ce71e3 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -3422,8 +3422,8 @@ NetProc* PCondit::elaborate(Design*des, NetScope*scope) const
 
 	// Well, I actually need to generate code to handle the
 	// conditional, so elaborate.
-      NetProc*i = if_? if_->elaborate(des, scope) : 0;
-      NetProc*e = else_? else_->elaborate(des, scope) : 0;
+      NetProc*i = if_? if_->elaborate(des, scope) : NULL;
+      NetProc*e = else_? else_->elaborate(des, scope) : NULL;
 
 	// Detect the special cases that the if or else statements are
 	// empty blocks. If this is the case, remove the blocks as
diff --git a/eval_tree.cc b/eval_tree.cc
index b9cb59e0e..e55305a51 100644
--- a/eval_tree.cc
+++ b/eval_tree.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -153,7 +153,7 @@ NetExpr* NetEBAdd::eval_tree()
 	// example, the expression (a + 2) - 1 can be rewritten as a + 1.
 
       NetEBAdd*se = dynamic_cast<NetEBAdd*>(left_);
-      NetEConst*lc = se? dynamic_cast<NetEConst*>(se->right_) : 0;
+      NetEConst*lc = se? dynamic_cast<NetEConst*>(se->right_) : NULL;
       NetEConst*rc = dynamic_cast<NetEConst*>(right_);
 
       if (lc != 0 && rc != 0) {
diff --git a/functor.cc b/functor.cc
index d32a5d36e..f54106a00 100644
--- a/functor.cc
+++ b/functor.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -176,7 +176,7 @@ void Design::functor(functor_t*fun)
 			break;
 
 		  nodes_functor_cur_ = nodes_functor_nxt_;
-	    } while (nodes_ && (nodes_functor_cur_ != nodes_));
+	    } while (nodes_functor_cur_ != nodes_);
 	    nodes_functor_cur_ = 0;
 	    nodes_functor_nxt_ = 0;
 
diff --git a/lexor.lex b/lexor.lex
index aca434fe9..14efed00b 100644
--- a/lexor.lex
+++ b/lexor.lex
@@ -80,7 +80,7 @@ char* yytext_string_filter(const char*str, size_t str_len)
 
 char* strdupnew(char const *str)
 {
-       return str ? strcpy(new char [strlen(str)+1], str) : 0;
+       return str ? strcpy(new char [strlen(str)+1], str) : NULL;
 }
 
 static const char* set_file_name(char*text)
diff --git a/main.cc b/main.cc
index 0c20b15cc..187ab9611 100644
--- a/main.cc
+++ b/main.cc
@@ -1,5 +1,5 @@
 const char COPYRIGHT[] =
-  "Copyright (c) 1998-2021 Stephen Williams (steve@icarus.com)";
+  "Copyright (c) 1998-2022 Stephen Williams (steve@icarus.com)";
 /*
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -1327,8 +1327,7 @@ int main(int argc, char*argv[])
 		  delete des;
 		  EOC_cleanup();
 		  return 1;
-	    }
-	    if (emit_rc < 0) {
+	    } else {
 		  cerr << "error: Code generator failure: " << emit_rc << endl;
 		  delete des;
 		  EOC_cleanup();
diff --git a/net_design.cc b/net_design.cc
index b9990365c..a94582901 100644
--- a/net_design.cc
+++ b/net_design.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -829,9 +829,9 @@ void NetScope::evaluate_type_parameter_(Design *des, param_ref_t cur)
 	    return;
       }
 
-      data_type_t *type = type_expr->get_type();
+      data_type_t *ptype = type_expr->get_type();
       NetScope *type_scope = cur->second.val_scope;
-      cur->second.ivl_type = type->elaborate_type(des, type_scope);
+      cur->second.ivl_type = ptype->elaborate_type(des, type_scope);
 }
 
 void NetScope::evaluate_parameter_(Design*des, param_ref_t cur)
diff --git a/net_event.cc b/net_event.cc
index fe1ce3455..ae2dd3ec8 100644
--- a/net_event.cc
+++ b/net_event.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -38,6 +38,7 @@ NetEvent::NetEvent(perm_string n)
       waitref_ = 0;
       exprref_ = 0;
       wlist_ = 0;
+      nb_trig_ = 0;
 }
 
 NetEvent::~NetEvent()
diff --git a/net_link.cc b/net_link.cc
index 05f1635fd..1f782bd8b 100644
--- a/net_link.cc
+++ b/net_link.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -33,7 +33,7 @@ using namespace std;
 
 void Nexus::connect(Link&r)
 {
-      Nexus*r_nexus = r.next_? r.find_nexus_() : 0;
+      Nexus*r_nexus = r.next_? r.find_nexus_() : NULL;
       if (this == r_nexus)
 	    return;
 
diff --git a/netclass.cc b/netclass.cc
index 99ad5d68a..e9b5e7480 100644
--- a/netclass.cc
+++ b/netclass.cc
@@ -24,7 +24,7 @@
 using namespace std;
 
 netclass_t::netclass_t(perm_string name, const netclass_t*super)
-: name_(name), super_(super), class_scope_(0), definition_scope_(0)
+: name_(name), super_(super), class_scope_(0), definition_scope_(0), virtual_class_(false)
 {
 }
 
diff --git a/netlist.h b/netlist.h
index 45cb82ee8..cf180df72 100644
--- a/netlist.h
+++ b/netlist.h
@@ -1,7 +1,7 @@
 #ifndef IVL_netlist_H
 #define IVL_netlist_H
 /*
- * Copyright (c) 1998-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1998-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -4061,7 +4061,7 @@ class NetProcTop  : public LineInfo, public Attrib {
     private:
       bool tie_off_floating_inputs_(Design*des,
 				    NexusSet&nex_map, NetBus&nex_in,
-				    std::vector<NetProc::mask_t>&bitmasks,
+				    const std::vector<NetProc::mask_t>&bitmasks,
 				    bool is_ff_input);
 
       const ivl_process_type_t type_;
diff --git a/netstruct.cc b/netstruct.cc
index 011a6540b..8d465c082 100644
--- a/netstruct.cc
+++ b/netstruct.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2011-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -27,7 +27,7 @@
 using namespace std;
 
 netstruct_t::netstruct_t()
-: union_(false), packed_(false)
+: union_(false), packed_(false), signed_(false)
 {
 }
 
diff --git a/netvector.h b/netvector.h
index 1bf919cec..97778d5d0 100644
--- a/netvector.h
+++ b/netvector.h
@@ -98,7 +98,7 @@ class netvector_t : public ivl_type_s {
 
 inline netvector_t::netvector_t(const std::vector<netrange_t>&pd,
 				ivl_variable_type_t type)
-: packed_dims_(pd), type_(type), signed_(false), isint_(false)
+: packed_dims_(pd), type_(type), signed_(false), isint_(false), implicit_(false)
 {
 }
 
diff --git a/pform.cc b/pform.cc
index 8cd13a4e1..a03b1209d 100644
--- a/pform.cc
+++ b/pform.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1998-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -1900,14 +1900,13 @@ void pform_make_udp(const struct vlltype&loc, perm_string name,
 	    perm_string port_name = (*decl)[idx]->basename();
 
 	    if (PWire*cur = defs[port_name]) {
-		  bool rc = true;
 		  assert((*decl)[idx]);
 		  if ((*decl)[idx]->get_port_type() != NetNet::PIMPLICIT) {
-			rc = cur->set_port_type((*decl)[idx]->get_port_type());
+			bool rc = cur->set_port_type((*decl)[idx]->get_port_type());
 			assert(rc);
 		  }
 		  if ((*decl)[idx]->get_wire_type() != NetNet::IMPLICIT) {
-			rc = cur->set_wire_type((*decl)[idx]->get_wire_type());
+			bool rc = cur->set_wire_type((*decl)[idx]->get_wire_type());
 			assert(rc);
 		  }
 
@@ -2770,7 +2769,7 @@ vector<pform_tf_port_t>*pform_make_task_ports(const struct vlltype&loc,
 
       for (list<pform_port_t>::iterator cur = ports->begin();
 	   cur != ports->end(); ++cur) {
-	    perm_string &name = cur->name;
+	    const perm_string &name = cur->name;
 
 	    PWire*curw = pform_get_or_make_wire(loc, name, NetNet::IMPLICIT_REG,
 						pt, rt);
@@ -2919,7 +2918,7 @@ LexicalScope::range_t* pform_parameter_value_range(bool exclude_flag,
 }
 
 static void pform_set_type_parameter(const struct vlltype&loc, perm_string name,
-				     LexicalScope::range_t*value_range)
+				     const LexicalScope::range_t*value_range)
 {
       pform_requires_sv(loc, "Type parameter");
 
diff --git a/synth2.cc b/synth2.cc
index c90d739f2..403baf842 100644
--- a/synth2.cc
+++ b/synth2.cc
@@ -192,7 +192,7 @@ static void merge_sequential_enables(Design*des, NetScope*scope,
       }
 }
 
-static void merge_sequential_masks(NetProc::mask_t&top_mask, NetProc::mask_t&sub_mask)
+static void merge_sequential_masks(NetProc::mask_t&top_mask, const NetProc::mask_t&sub_mask)
 {
       if (sub_mask.size() == 0)
 	    return;
@@ -209,7 +209,7 @@ static void merge_sequential_masks(NetProc::mask_t&top_mask, NetProc::mask_t&sub
       }
 }
 
-static void merge_parallel_masks(NetProc::mask_t&top_mask, NetProc::mask_t&sub_mask)
+static void merge_parallel_masks(NetProc::mask_t&top_mask, const NetProc::mask_t&sub_mask)
 {
       if (sub_mask.size() == 0)
 	    return;
@@ -226,7 +226,7 @@ static void merge_parallel_masks(NetProc::mask_t&top_mask, NetProc::mask_t&sub_m
       }
 }
 
-static bool all_bits_driven(NetProc::mask_t&mask)
+static bool all_bits_driven(const NetProc::mask_t&mask)
 {
       if (mask.size() == 0)
 	    return false;
@@ -240,7 +240,7 @@ static bool all_bits_driven(NetProc::mask_t&mask)
 
 bool NetProcTop::tie_off_floating_inputs_(Design*des,
 					  NexusSet&nex_map, NetBus&nex_in,
-					  vector<NetProc::mask_t>&bitmasks,
+					  const vector<NetProc::mask_t>&bitmasks,
 					  bool is_ff_input)
 {
       bool flag = true;
@@ -1380,8 +1380,8 @@ bool NetCondit::synth_async(Design*des, NetScope*scope,
 		  delete bpv;
 	    } else {
 		    // The part selects are of no use. Forget them.
-		  apv = 0;
-		  bpv = 0;
+		  if (apv) delete apv;
+		  if (bpv) delete bpv;
 	    }
 
 	    NetMux*mux = new NetMux(scope, scope->local_symbol(),
diff --git a/t-dll.cc b/t-dll.cc
index e81f74e68..b009f14f8 100644
--- a/t-dll.cc
+++ b/t-dll.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2022 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -261,16 +261,16 @@ ivl_scope_t dll_target::find_scope(ivl_design_s &des, const NetScope*cur)
 
       for (unsigned idx = 0; idx < des.roots.size(); idx += 1) {
 	    assert(des.roots[idx]);
-	    ivl_scope_t scope = find_scope_from_root(des.roots[idx], cur);
-	    if (scope)
-		  return scope;
+	    ivl_scope_t scop = find_scope_from_root(des.roots[idx], cur);
+	    if (scop)
+		  return scop;
       }
 
       for (size_t idx = 0; idx < des.packages.size(); idx += 1) {
 	    assert(des.packages[idx]);
-	    ivl_scope_t scope = find_scope_from_root(des.packages[idx], cur);
-	    if (scope)
-		  return scope;
+	    ivl_scope_t scop = find_scope_from_root(des.packages[idx], cur);
+	    if (scop)
+		  return scop;
       }
 
       return 0;
@@ -287,14 +287,14 @@ ivl_scope_t dll_target::lookup_scope_(const NetScope*cur)
  */
 ivl_signal_t dll_target::find_signal(ivl_design_s &des, const NetNet*net)
 {
-      ivl_scope_t scope = find_scope(des, net->scope());
-      assert(scope);
+      ivl_scope_t scop = find_scope(des, net->scope());
+      assert(scop);
 
       perm_string nname = net->name();
 
-      for (unsigned idx = 0 ;  idx < scope->sigs_.size() ;  idx += 1) {
-	    if (strcmp(scope->sigs_[idx]->name_, nname) == 0)
-		  return scope->sigs_[idx];
+      for (unsigned idx = 0 ;  idx < scop->sigs_.size() ;  idx += 1) {
+	    if (strcmp(scop->sigs_[idx]->name_, nname) == 0)
+		  return scop->sigs_[idx];
       }
 
       assert(0);
@@ -2744,7 +2744,7 @@ void dll_target::signal(const NetNet*net)
 
       for (unsigned idx = 0 ;  idx < obj->array_words ;  idx += 1) {
 
-	    const Nexus*nex = net->pins_are_virtual() ? 0 : net->pin(idx).nexus();
+	    const Nexus*nex = net->pins_are_virtual() ? NULL : net->pin(idx).nexus();
 	    if (nex == 0) {
 		    // Special case: This pin is connected to
 		    // nothing. This can happen, for example, if the
diff --git a/tgt-blif/blif.cc b/tgt-blif/blif.cc
index 59803fccb..5b7016438 100644
--- a/tgt-blif/blif.cc
+++ b/tgt-blif/blif.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2020 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2013-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -222,7 +222,7 @@ static void emit_blif(const char*blif_path, ivl_design_t des, ivl_scope_t model)
       fclose(fd);
 }
 
-bool scope_is_in_model(ivl_scope_t model, ivl_scope_t scope)
+bool scope_is_in_model(const ivl_scope_t model, ivl_scope_t scope)
 {
       while (scope) {
 	    if (scope==model)
diff --git a/tgt-vlog95/logic_lpm.c b/tgt-vlog95/logic_lpm.c
index 24dfdc146..6f86d2d42 100644
--- a/tgt-vlog95/logic_lpm.c
+++ b/tgt-vlog95/logic_lpm.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2021 Cary R. (cygcary@yahoo.com)
+ * Copyright (C) 2011-2022 Cary R. (cygcary@yahoo.com)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -345,7 +345,7 @@ static void emit_driver_delay(ivl_scope_t scope, ivl_nexus_t nex)
       emit_delay(scope, rise, fall, decay, 3);
 }
 
-static unsigned is_local_nexus(ivl_scope_t scope, ivl_nexus_t nex)
+static unsigned is_local_nexus(const ivl_scope_t scope, ivl_nexus_t nex)
 {
       unsigned idx, count = ivl_nexus_ptrs(nex);
       unsigned is_local = 1;
@@ -469,7 +469,7 @@ static void emit_nexus_port_signal(ivl_scope_t scope, ivl_nexus_t nex)
       else fprintf(vlog_out, "/* Empty */");
 }
 
-static ivl_signal_t find_local_signal(ivl_scope_t scope, ivl_nexus_t nex,
+static ivl_signal_t find_local_signal(const ivl_scope_t scope, ivl_nexus_t nex,
                                       unsigned *word)
 {
       unsigned idx, count = ivl_nexus_ptrs(nex);
@@ -817,7 +817,7 @@ static void emit_lpm_concat(ivl_scope_t scope, ivl_lpm_t lpm)
 /*
  * Look for an output signal in the nexus that is driving into this scope.
  */
-static ivl_signal_t find_output_signal(ivl_scope_t scope, ivl_nexus_t nex,
+static ivl_signal_t find_output_signal(const ivl_scope_t scope, ivl_nexus_t nex,
                                        unsigned*array_word)
 {
       unsigned idx, count = ivl_nexus_ptrs(nex);
@@ -961,9 +961,8 @@ static void emit_lpm_part_select(ivl_scope_t scope, ivl_lpm_t lpm,
 	    return;
       }
 
-      if (sign_extend) fprintf(vlog_out, "(");
-
       if (sign_extend) {
+	    fprintf(vlog_out, "(");
 	    assert(base != lsb);
 // HERE: This looks wrong.
 	    if (msb >= lsb) base += lsb;
@@ -1771,7 +1770,7 @@ static void emit_lpm_latch(ivl_scope_t scope, ivl_lpm_t lpm)
       need_latch_prim = 1;
 }
 
-static ivl_signal_t get_output_from_nexus(ivl_scope_t scope, ivl_nexus_t nex,
+static ivl_signal_t get_output_from_nexus(const ivl_scope_t scope, ivl_nexus_t nex,
                                           int64_t*array_idx)
 {
       ivl_signal_t use_sig = 0;
@@ -1858,8 +1857,8 @@ static void emit_lpm_part_pv(ivl_scope_t scope, ivl_lpm_t lpm)
       fprintf(vlog_out, "]");
 }
 
-static unsigned  output_is_module_instantiation_input(ivl_scope_t scope,
-                                               ivl_nexus_t nex)
+static unsigned output_is_module_instantiation_input(const ivl_scope_t scope,
+                                                     ivl_nexus_t nex)
 {
       unsigned idx, count = ivl_nexus_ptrs(nex);
       unsigned rtn = 0;
diff --git a/tgt-vlog95/misc.c b/tgt-vlog95/misc.c
index 57be52a78..8c2b8c2c8 100644
--- a/tgt-vlog95/misc.c
+++ b/tgt-vlog95/misc.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2020 Cary R. (cygcary@yahoo.com)
+ * Copyright (C) 2011-2022 Cary R. (cygcary@yahoo.com)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -420,7 +420,7 @@ void emit_scaled_expr(ivl_scope_t scope, ivl_expr_t expr, int msb, int lsb)
       }
 }
 
-static unsigned find_signal_in_nexus(ivl_scope_t scope, ivl_nexus_t nex)
+static unsigned find_signal_in_nexus(const ivl_scope_t scope, ivl_nexus_t nex)
 {
       ivl_signal_t use_sig = 0;
       unsigned is_driver = 0;
diff --git a/tgt-vlog95/scope.c b/tgt-vlog95/scope.c
index 81177cd83..899052117 100644
--- a/tgt-vlog95/scope.c
+++ b/tgt-vlog95/scope.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010-2021 Cary R. (cygcary@yahoo.com)
+ * Copyright (C) 2010-2022 Cary R. (cygcary@yahoo.com)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -171,7 +171,7 @@ static unsigned emit_and_free_net_const_list(ivl_scope_t scope)
       return idx;
 }
 
-static void save_net_constants(ivl_scope_t scope, ivl_signal_t sig)
+static void save_net_constants(const ivl_scope_t scope, ivl_signal_t sig)
 {
       ivl_nexus_t nex = ivl_signal_nex(sig, 0);
       unsigned idx, count = ivl_nexus_ptrs(nex);
@@ -397,7 +397,7 @@ static void emit_module_ports(ivl_scope_t scope)
       fprintf(vlog_out, ")");
 }
 
-static ivl_signal_t get_port_from_nexus(ivl_scope_t scope, ivl_nexus_t nex,
+static ivl_signal_t get_port_from_nexus(const ivl_scope_t scope, ivl_nexus_t nex,
 	                                unsigned *word)
 {
       assert(nex);
@@ -1015,7 +1015,7 @@ static ivl_scope_t *scopes_to_emit = 0;
 static unsigned num_scopes_to_emit = 0;
 static unsigned emitting_scopes = 0;
 
-int emit_scope(ivl_scope_t scope, ivl_scope_t parent)
+int emit_scope(ivl_scope_t scope, const ivl_scope_t parent)
 {
       char *package_name = 0;
       ivl_scope_type_t sc_type = ivl_scope_type(scope);
diff --git a/tgt-vlog95/stmt.c b/tgt-vlog95/stmt.c
index 1a14771df..f94733305 100644
--- a/tgt-vlog95/stmt.c
+++ b/tgt-vlog95/stmt.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2021 Cary R. (cygcary@yahoo.com)
+ * Copyright (C) 2011-2022 Cary R. (cygcary@yahoo.com)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -1085,7 +1085,7 @@ static void emit_stmt_delayx(ivl_scope_t scope, ivl_statement_t stmt)
       emit_stmt(scope, ivl_stmt_sub_stmt(stmt));
 }
 
-static unsigned is_func_disable(ivl_scope_t scope, ivl_scope_t disable_scope)
+static unsigned is_func_disable(ivl_scope_t scope, const ivl_scope_t disable_scope)
 {
       assert(func_rtn_name);
 	/* Find the enclosing function scope. */
diff --git a/tgt-vvp/draw_net_input.c b/tgt-vvp/draw_net_input.c
index 45e753b06..53f94f908 100644
--- a/tgt-vvp/draw_net_input.c
+++ b/tgt-vvp/draw_net_input.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2020 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -280,7 +280,7 @@ static char* draw_net_pull(ivl_net_logic_t lptr, ivl_drive_t drive, const char*l
  * to this nexus.
  */
 
-static char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
+static char* draw_net_input_drive(const ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 {
       unsigned nptr_pin = ivl_nexus_ptr_pin(nptr);
       ivl_net_const_t cptr;
@@ -817,7 +817,7 @@ const char*draw_net_input(ivl_nexus_t nex)
       return nex_data->net_input;
 }
 
-const char*draw_island_net_input(ivl_island_t island, ivl_nexus_t nex)
+const char*draw_island_net_input(const ivl_island_t island, ivl_nexus_t nex)
 {
       struct vvp_nexus_data*nex_data = (struct vvp_nexus_data*)
 	    ivl_nexus_get_private(nex);
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index 5ef76a200..e8e4e4ec5 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -262,7 +262,7 @@ const char*drive_string(ivl_drive_t drive)
  * to netlist signals. This routine performs this check on the
  * given nexus.
  */
-static unsigned is_netlist_signal(ivl_net_logic_t net, ivl_nexus_t nex)
+static unsigned is_netlist_signal(const ivl_net_logic_t net, ivl_nexus_t nex)
 {
       unsigned idx, rtn;
 
diff --git a/vpi/cppcheck.sup b/vpi/cppcheck.sup
index 3990c3cb1..63f17c522 100644
--- a/vpi/cppcheck.sup
+++ b/vpi/cppcheck.sup
@@ -3,177 +3,184 @@
 // problems will not be fixed.
 
 // fstapi.c from GTKWave
-asctimeCalled:fstapi.c:955
-allocaCalled:fstapi.c:2386
-unreadVariable:fstapi.c:204
-unreadVariable:fstapi.c:205
-unreadVariable:fstapi.c:1645
-unreadVariable:fstapi.c:1653
-unreadVariable:fstapi.c:1657
-unreadVariable:fstapi.c:1662
-unreadVariable:fstapi.c:1685
-unreadVariable:fstapi.c:1691
-unreadVariable:fstapi.c:1692
-unreadVariable:fstapi.c:1696
-unreadVariable:fstapi.c:2818
-unreadVariable:fstapi.c:6521
-variableScope:fstapi.c:684
-variableScope:fstapi.c:1078
-variableScope:fstapi.c:1385
-variableScope:fstapi.c:1386
-variableScope:fstapi.c:1387
-variableScope:fstapi.c:1444
-variableScope:fstapi.c:2056
-variableScope:fstapi.c:2189
-variableScope:fstapi.c:2622
-variableScope:fstapi.c:2623
-variableScope:fstapi.c:2812
-variableScope:fstapi.c:2813
-variableScope:fstapi.c:2814
-variableScope:fstapi.c:2815
-variableScope:fstapi.c:2816
-variableScope:fstapi.c:2817
-variableScope:fstapi.c:2818
-variableScope:fstapi.c:2919
-variableScope:fstapi.c:2920
-variableScope:fstapi.c:2924
-variableScope:fstapi.c:3161
-variableScope:fstapi.c:3200
-variableScope:fstapi.c:3201
-variableScope:fstapi.c:3920
-variableScope:fstapi.c:4098
-variableScope:fstapi.c:4100
-variableScope:fstapi.c:4542
-variableScope:fstapi.c:4543
-variableScope:fstapi.c:4552
-variableScope:fstapi.c:4815
-variableScope:fstapi.c:5086
-variableScope:fstapi.c:5089
-variableScope:fstapi.c:5585
-variableScope:fstapi.c:5589
-variableScope:fstapi.c:5590
-variableScope:fstapi.c:5748
-variableScope:fstapi.c:5806
-variableScope:fstapi.c:6119
-variableScope:fstapi.c:6122
-variableScope:fstapi.c:6416
-variableScope:fstapi.c:6521
-variableScope:fstapi.c:6522
-variableScope:fstapi.c:6553
-variableScope:fstapi.c:6781
-variableScope:fstapi.c:6957
-variableScope:fstapi.c:6958
-variableScope:fstapi.c:6959
+asctimeCalled:fstapi.c:965
+allocaCalled:fstapi.c:2396
+unreadVariable:fstapi.c:214
+unreadVariable:fstapi.c:215
+unreadVariable:fstapi.c:1655
+unreadVariable:fstapi.c:1663
+unreadVariable:fstapi.c:1667
+unreadVariable:fstapi.c:1672
+unreadVariable:fstapi.c:1695
+unreadVariable:fstapi.c:1701
+unreadVariable:fstapi.c:1702
+unreadVariable:fstapi.c:1706
+unreadVariable:fstapi.c:2828
+unreadVariable:fstapi.c:6555
+variableScope:fstapi.c:694
+variableScope:fstapi.c:1088
+variableScope:fstapi.c:1395
+variableScope:fstapi.c:1396
+variableScope:fstapi.c:1397
+variableScope:fstapi.c:1454
+variableScope:fstapi.c:1944
+variableScope:fstapi.c:2064
+variableScope:fstapi.c:2066
+variableScope:fstapi.c:2187
+variableScope:fstapi.c:2199
+variableScope:fstapi.c:2632
+variableScope:fstapi.c:2633
+variableScope:fstapi.c:2822
+variableScope:fstapi.c:2823
+variableScope:fstapi.c:2824
+variableScope:fstapi.c:2825
+variableScope:fstapi.c:2826
+variableScope:fstapi.c:2827
+variableScope:fstapi.c:2828
+variableScope:fstapi.c:2929
+variableScope:fstapi.c:2930
+variableScope:fstapi.c:2934
+variableScope:fstapi.c:3171
+variableScope:fstapi.c:3210
+variableScope:fstapi.c:3211
+variableScope:fstapi.c:3927
+variableScope:fstapi.c:3930
+variableScope:fstapi.c:4108
+variableScope:fstapi.c:4110
+variableScope:fstapi.c:4578
+variableScope:fstapi.c:4579
+variableScope:fstapi.c:4582
+variableScope:fstapi.c:4583
+variableScope:fstapi.c:4591
+variableScope:fstapi.c:4592
+variableScope:fstapi.c:4854
+variableScope:fstapi.c:5120
+variableScope:fstapi.c:5123
+variableScope:fstapi.c:5619
+variableScope:fstapi.c:5623
+variableScope:fstapi.c:5624
+variableScope:fstapi.c:5782
+variableScope:fstapi.c:5840
+variableScope:fstapi.c:6153
+variableScope:fstapi.c:6156
+variableScope:fstapi.c:6450
+variableScope:fstapi.c:6555
+variableScope:fstapi.c:6556
+variableScope:fstapi.c:6587
+variableScope:fstapi.c:6815
+variableScope:fstapi.c:6991
+variableScope:fstapi.c:6992
+variableScope:fstapi.c:6993
 
 // These functions are not used by Icarus
 // fstReaderClrFacProcessMask()
-unusedFunction:fstapi.c:3652
+unusedFunction:fstapi.c:3662
 // fstReaderClrFacProcessMaskAll()
-unusedFunction:fstapi.c:3681
+unusedFunction:fstapi.c:3691
 // fstReaderGetAliasCount()
-unusedFunction:fstapi.c:3744
+unusedFunction:fstapi.c:3754
 // fstReaderGetCurrentFlatScope()
-unusedFunction:fstapi.c:3490
+unusedFunction:fstapi.c:3500
 // fstReaderGetCurrentScopeLen()
-unusedFunction:fstapi.c:3587
+unusedFunction:fstapi.c:3597
 // fstReaderGetCurrentScopeUserInfo()
-unusedFunction:fstapi.c:3504
+unusedFunction:fstapi.c:3514
 // fstReaderGetDateString()
-unusedFunction:fstapi.c:3772
+unusedFunction:fstapi.c:3782
 // fstReaderGetDoubleEndianMatchState()
-unusedFunction:fstapi.c:3758
+unusedFunction:fstapi.c:3768
 // fstReaderGetDumpActivityChangeTime()
-unusedFunction:fstapi.c:3800
+unusedFunction:fstapi.c:3810
 // fstReaderGetDumpActivityChangeValue()
-unusedFunction:fstapi.c:3815
+unusedFunction:fstapi.c:3825
 // fstReaderGetEndTime()
-unusedFunction:fstapi.c:3709
+unusedFunction:fstapi.c:3719
 // fstReaderGetFacProcessMask()
-unusedFunction:fstapi.c:3615
+unusedFunction:fstapi.c:3625
 // fstReaderGetFileType()
-unusedFunction:fstapi.c:3779
+unusedFunction:fstapi.c:3789
 // fstReaderGetFseekFailed()
-unusedFunction:fstapi.c:3600
+unusedFunction:fstapi.c:3610
 // fstReaderGetMaxHandle()
-unusedFunction:fstapi.c:3737
+unusedFunction:fstapi.c:3747
 // fstReaderGetMemoryUsedByWriter()
-unusedFunction:fstapi.c:3716
+unusedFunction:fstapi.c:3726
 // fstReaderGetNumberDumpActivityChanges()
-unusedFunction:fstapi.c:3793
+unusedFunction:fstapi.c:3803
 // fstReaderGetScopeCount()
-unusedFunction:fstapi.c:3723
+unusedFunction:fstapi.c:3733
 // fstReaderGetStartTime()
-unusedFunction:fstapi.c:3702
+unusedFunction:fstapi.c:3712
 // fstReaderGetTimescale()
-unusedFunction:fstapi.c:3695
+unusedFunction:fstapi.c:3705
 // fstReaderGetTimezero()
-unusedFunction:fstapi.c:3786
+unusedFunction:fstapi.c:3796
 // fstReaderGetValueChangeSectionCount()
-unusedFunction:fstapi.c:3751
+unusedFunction:fstapi.c:3761
 // fstReaderGetValueFromHandleAtTime()
-unusedFunction:fstapi.c:6001
+unusedFunction:fstapi.c:6035
 // fstReaderGetVarCount()
-unusedFunction:fstapi.c:3730
+unusedFunction:fstapi.c:3740
 // fstReaderGetVersionString()
-unusedFunction:fstapi.c:3765
+unusedFunction:fstapi.c:3775
 // fstReaderIterBlocks()
-unusedFunction:fstapi.c:4964
+unusedFunction:fstapi.c:5003
 // fstReaderIterBlocksSetNativeDoublesOnCallback()
-unusedFunction:fstapi.c:3865
+unusedFunction:fstapi.c:3875
 // fstReaderIterateHier()
-unusedFunction:fstapi.c:4094
+unusedFunction:fstapi.c:4104
 // fstReaderIterateHierRewind()
-unusedFunction:fstapi.c:4074
+unusedFunction:fstapi.c:4084
 // fstReaderOpen()
-unusedFunction:fstapi.c:4862
+unusedFunction:fstapi.c:4901
 // fstReaderOpenForUtilitiesOnly()
-unusedFunction:fstapi.c:4854
+unusedFunction:fstapi.c:4893
 // fstReaderPushScope()
-unusedFunction:fstapi.c:3552
+unusedFunction:fstapi.c:3562
 // fstReaderResetScope()
-unusedFunction:fstapi.c:3541
+unusedFunction:fstapi.c:3551
 // fstReaderSetFacProcessMask()
-unusedFunction:fstapi.c:3634
+unusedFunction:fstapi.c:3644
 // fstReaderSetFacProcessMaskAll()
-unusedFunction:fstapi.c:3670
+unusedFunction:fstapi.c:3680
 // fstReaderSetLimitTimeRange()
-unusedFunction:fstapi.c:3830
+unusedFunction:fstapi.c:3840
 // fstReaderSetUnlimitedTimeRange()
-unusedFunction:fstapi.c:3843
+unusedFunction:fstapi.c:3853
 // fstReaderSetVcdExtensions()
-unusedFunction:fstapi.c:3854
+unusedFunction:fstapi.c:3864
 // fstUtilityExtractEnumTableFromString()
-unusedFunction:fstapi.c:6954
+unusedFunction:fstapi.c:6988
 // fstUtilityFreeEnumTable()
-unusedFunction:fstapi.c:7015
+unusedFunction:fstapi.c:7049
 // fstWriterCreateEnumTable()
-unusedFunction:fstapi.c:2807
+unusedFunction:fstapi.c:2817
 // fstWriterCreateVar2()
-unusedFunction:fstapi.c:2609
+unusedFunction:fstapi.c:2619
 // fstWriterEmitEnumTableRef()
-unusedFunction:fstapi.c:2902
+unusedFunction:fstapi.c:2912
 // fstWriterEmitValueChangeVec32()
-unusedFunction:fstapi.c:3054
+unusedFunction:fstapi.c:3064
 // fstWriterEmitValueChangeVec64()
-unusedFunction:fstapi.c:3103
+unusedFunction:fstapi.c:3113
 // fstWriterEmitVariableLengthValueChange()
-unusedFunction:fstapi.c:3154
+unusedFunction:fstapi.c:3164
 // fstWriterGetFseekFailed()
-unusedFunction:fstapi.c:2592
+unusedFunction:fstapi.c:2602
 // fstWriterSetAttrEnd()
-unusedFunction:fstapi.c:2795
+unusedFunction:fstapi.c:2805
 // fstWriterSetComment()
-unusedFunction:fstapi.c:2441
+unusedFunction:fstapi.c:2451
 // fstWriterSetEnvVar()
-unusedFunction:fstapi.c:2453
+unusedFunction:fstapi.c:2463
 // fstWriterSetFileType()
-unusedFunction:fstapi.c:2316
+unusedFunction:fstapi.c:2326
 // fstWriterSetParallelMode()
-unusedFunction:fstapi.c:2552
+unusedFunction:fstapi.c:2562
 // fstWriterSetTimezero()
-unusedFunction:fstapi.c:2517
+unusedFunction:fstapi.c:2527
 // fstWriterSetValueList()
-unusedFunction:fstapi.c:2447
+unusedFunction:fstapi.c:2457
 
 // lxt2_write.c from GTKWave
 allocaCalled:lxt2_write.c:1813
@@ -335,7 +342,7 @@ unusedFunction:lz4.c:376
 
 // The routines in sys_random.c are exact copies from IEEE1364-2005 and
 // they have scope warnings that we need to ignore.
-variableScope:sys_random.c:46
-variableScope:sys_random.c:69
-variableScope:sys_random.c:92
-variableScope:sys_random.c:147
+variableScope:sys_random.c:47
+variableScope:sys_random.c:70
+variableScope:sys_random.c:93
+variableScope:sys_random.c:148
diff --git a/vpi/mt19937int.c b/vpi/mt19937int.c
index ac6fe01e0..73eaad068 100644
--- a/vpi/mt19937int.c
+++ b/vpi/mt19937int.c
@@ -1,5 +1,5 @@
 /*
- * NOTE: This code as been slightly modified to interface with the
+ * NOTE: This code has been slightly modified to interface with the
  * PLI implementations of $random. The copyright and license
  * information are given in the comment block below.
  *
@@ -89,7 +89,7 @@ genrand(struct context_s *context)
 
     if (mti >= N) { /* generate N words at one time */
 	/* mag01[x] = x * MATRIX_A  for x=0,1 */
-	static unsigned long mag01[2]={0x0, MATRIX_A};
+	static const unsigned long mag01[2]={0x0, MATRIX_A};
         int kk;
 
         if (mti == N+1)   /* if sgenrand() has not been called, */
diff --git a/vvp/array.cc b/vvp/array.cc
index 4727a4ebf..bb8b539fc 100644
--- a/vvp/array.cc
+++ b/vvp/array.cc
@@ -334,7 +334,7 @@ int __vpiArrayWord::as_word_t::vpi_get(int code)
 {
       struct __vpiArrayWord*obj = array_var_word_from_handle(this);
       assert(obj);
-      struct __vpiArrayBase*parent = obj->get_parent();
+      struct __vpiArrayBase*my_parent = obj->get_parent();
       t_vpi_value val;
 
       switch (code) {
@@ -342,24 +342,24 @@ int __vpiArrayWord::as_word_t::vpi_get(int code)
 	    return 0; // Not implemented for now!
 
 	  case vpiSize:
-	    return parent->get_word_size();
+	    return my_parent->get_word_size();
 
 	  case vpiLeftRange:
             val.format = vpiIntVal;
-	    parent->get_left_range()->vpi_get_value(&val);
+	    my_parent->get_left_range()->vpi_get_value(&val);
             assert(val.format == vpiIntVal);
             return val.value.integer;
 
 	  case vpiRightRange:
             val.format = vpiIntVal;
-	    parent->get_right_range()->vpi_get_value(&val);
+	    my_parent->get_right_range()->vpi_get_value(&val);
             assert(val.format == vpiIntVal);
             return val.value.integer;
 
 	  case vpiIndex:
 	    {
 		  int base_offset = 0;
-		  struct __vpiArray*base = dynamic_cast<__vpiArray*> (parent);
+		  struct __vpiArray*base = dynamic_cast<__vpiArray*> (my_parent);
 		  if (base) {
 			val.format = vpiIntVal;
 			base->first_addr.vpi_get_value(&val);
@@ -372,7 +372,7 @@ int __vpiArrayWord::as_word_t::vpi_get(int code)
 	    }
 
 	  case vpiAutomatic:
-	    return parent->get_scope()->is_automatic()? 1 : 0;
+	    return my_parent->get_scope()->is_automatic()? 1 : 0;
 
 #if defined(CHECK_WITH_VALGRIND) || defined(BR916_STOPGAP_FIX)
 	  case _vpiFromThr:
diff --git a/vvp/array_common.cc b/vvp/array_common.cc
index 59d928df9..2fefbf1c1 100644
--- a/vvp/array_common.cc
+++ b/vvp/array_common.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2014-2022 Stephen Williams (steve@icarus.com)
  * Copyright (c) 2014 CERN
  * @author Maciej Suminski <maciej.suminski@cern.ch>
  *
@@ -116,24 +116,24 @@ char* __vpiArrayWord::as_word_t::vpi_get_str(int code)
 {
       struct __vpiArrayWord*obj = array_var_word_from_handle(this);
       assert(obj);
-      struct __vpiArrayBase*parent = obj->get_parent();
-      return parent->get_word_str(obj, code);
+      struct __vpiArrayBase*my_parent = obj->get_parent();
+      return my_parent->get_word_str(obj, code);
 }
 
 void __vpiArrayWord::as_word_t::vpi_get_value(p_vpi_value vp)
 {
       struct __vpiArrayWord*obj = array_var_word_from_handle(this);
       assert(obj);
-      struct __vpiArrayBase*parent = obj->get_parent();
-      return parent->get_word_value(obj, vp);
+      struct __vpiArrayBase*my_parent = obj->get_parent();
+      return my_parent->get_word_value(obj, vp);
 }
 
 vpiHandle __vpiArrayWord::as_word_t::vpi_put_value(p_vpi_value vp, int flags)
 {
       struct __vpiArrayWord*obj = array_var_word_from_handle(this);
       assert(obj);
-      struct __vpiArrayBase*parent = obj->get_parent();
-      parent->put_word_value(obj, vp, flags);
+      struct __vpiArrayBase*my_parent = obj->get_parent();
+      my_parent->put_word_value(obj, vp, flags);
       return this;
 }
 
@@ -141,7 +141,7 @@ vpiHandle __vpiArrayWord::as_word_t::vpi_handle(int code)
 {
       struct __vpiArrayWord*obj = array_var_word_from_handle(this);
       assert(obj);
-      struct __vpiArrayBase*parent = obj->get_parent();
+      struct __vpiArrayBase*my_parent = obj->get_parent();
 
       switch (code) {
 
@@ -149,19 +149,19 @@ vpiHandle __vpiArrayWord::as_word_t::vpi_handle(int code)
 	    return &(obj->as_index);
 
 	  case vpiLeftRange:
-	    return parent->get_left_range();
+	    return my_parent->get_left_range();
 
 	  case vpiRightRange:
-	    return parent->get_right_range();
+	    return my_parent->get_right_range();
 
 	  case vpiParent:
-	    return dynamic_cast<vpiHandle>(parent);
+	    return dynamic_cast<vpiHandle>(my_parent);
 
 	  case vpiScope:
-	    return parent->get_scope();
+	    return my_parent->get_scope();
 
 	  case vpiModule:
-	    return vpip_module(parent->get_scope());
+	    return vpip_module(my_parent->get_scope());
       }
 
       return 0;
diff --git a/vvp/cppcheck.sup b/vvp/cppcheck.sup
index 1d0fe930b..a3135f088 100644
--- a/vvp/cppcheck.sup
+++ b/vvp/cppcheck.sup
@@ -1,6 +1,6 @@
 // The new() operator is always used to allocate space for this class and
 // pool is defined there.
-uninitMemberVar:vvp_net.cc:190
+uninitMemberVar:vvp_net.cc:192
 
 // These functions are not used by Icarus
 // vpi_chk_error()
diff --git a/vvp/island_tran.cc b/vvp/island_tran.cc
index cdb3946a6..b5282c424 100644
--- a/vvp/island_tran.cc
+++ b/vvp/island_tran.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2008-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -185,7 +185,7 @@ void vvp_island_tran::count_drivers(vvp_island_port*port, unsigned bit_idx,
 
 void vvp_island_branch_tran::run_test_enabled()
 {
-      vvp_island_port*ep = en? dynamic_cast<vvp_island_port*> (en->fun) : 0;
+      vvp_island_port*ep = en? dynamic_cast<vvp_island_port*> (en->fun) : NULL;
 
 	// If there is no ep port (no "enabled" input) then this is a
 	// tran branch. Assume it is always enabled.
diff --git a/vvp/parse.y b/vvp/parse.y
index 5ac94bdf5..1224fa21a 100644
--- a/vvp/parse.y
+++ b/vvp/parse.y
@@ -1,7 +1,7 @@
 
 %{
 /*
- * Copyright (c) 2001-202` Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
diff --git a/vvp/vpi_callback.cc b/vvp/vpi_callback.cc
index dfd9d4d8c..80a640186 100644
--- a/vvp/vpi_callback.cc
+++ b/vvp/vpi_callback.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -461,7 +461,7 @@ static struct __vpiCallback* make_at_end_of_sim_time(p_cb_data data)
 
 class simulator_callback : public __vpiCallback {
     public:
-      inline explicit simulator_callback(struct t_cb_data*data)
+      inline explicit simulator_callback(const struct t_cb_data*data)
       { cb_data = *data; }
 
     public:
diff --git a/vvp/vpi_cobject.cc b/vvp/vpi_cobject.cc
index 4bcee73d5..d0343e3d2 100644
--- a/vvp/vpi_cobject.cc
+++ b/vvp/vpi_cobject.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2021 Picture Elements, Inc.
+ * Copyright (c) 2012-2022 Picture Elements, Inc.
  *    Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -117,7 +117,7 @@ void __vpiCobjectVar::vpi_get_value(p_vpi_value val)
 vpiHandle vpip_make_cobject_var(const char*name, vvp_net_t*net)
 {
       __vpiScope*scope = vpip_peek_current_scope();
-      const char*use_name = name ? vpip_name_string(name) : 0;
+      const char*use_name = name ? vpip_name_string(name) : NULL;
 
       __vpiCobjectVar*obj = new __vpiCobjectVar(scope, use_name, net);
 
diff --git a/vvp/vpi_darray.cc b/vvp/vpi_darray.cc
index bc63ff741..6edde31d0 100644
--- a/vvp/vpi_darray.cc
+++ b/vvp/vpi_darray.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2012-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -286,7 +286,7 @@ vvp_darray*__vpiDarrayVar::get_vvp_darray() const
 vpiHandle vpip_make_darray_var(const char*name, vvp_net_t*net)
 {
       __vpiScope*scope = vpip_peek_current_scope();
-      const char*use_name = name ? vpip_name_string(name) : 0;
+      const char*use_name = name ? vpip_name_string(name) : NULL;
 
       __vpiDarrayVar*obj = new __vpiDarrayVar(scope, use_name, net);
 
@@ -332,7 +332,7 @@ void __vpiQueueVar::vpi_get_value(p_vpi_value val)
 vpiHandle vpip_make_queue_var(const char*name, vvp_net_t*net)
 {
       __vpiScope*scope = vpip_peek_current_scope();
-      const char*use_name = name ? vpip_name_string(name) : 0;
+      const char*use_name = name ? vpip_name_string(name) : NULL;
 
       __vpiQueueVar*obj = new __vpiQueueVar(scope, use_name, net);
 
diff --git a/vvp/vpi_priv.cc b/vvp/vpi_priv.cc
index 99cc8a20c..ff11cfe9e 100644
--- a/vvp/vpi_priv.cc
+++ b/vvp/vpi_priv.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2008-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -1057,7 +1057,7 @@ void vpip_put_value_event::run_run()
 }
 
 /* Make a copy of a pointer to a time structure. */
-static t_vpi_time *timedup(t_vpi_time *val)
+static t_vpi_time *timedup(const t_vpi_time *val)
 {
       t_vpi_time *rtn;
       rtn = static_cast<t_vpi_time *> (malloc(sizeof(t_vpi_time)));
@@ -1078,7 +1078,7 @@ static t_vpi_vecval *vectordup(t_vpi_vecval *val, PLI_INT32 size)
 }
 
 /* Make a copy of a pointer to a strength structure. */
-static t_vpi_strengthval *strengthdup(t_vpi_strengthval *val)
+static t_vpi_strengthval *strengthdup(const t_vpi_strengthval *val)
 {
       t_vpi_strengthval *rtn;
       rtn = static_cast<t_vpi_strengthval *>
diff --git a/vvp/vpi_real.cc b/vvp/vpi_real.cc
index e51ee3219..23f63c53d 100644
--- a/vvp/vpi_real.cc
+++ b/vvp/vpi_real.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2015 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2003-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -86,10 +86,10 @@ static vpiHandle real_var_get_handle(int code, vpiHandle ref)
       switch (code) {
 
 	  case vpiParent:
-	    return rfp->is_netarray ? rfp->within.parent : 0;
+	    return rfp->is_netarray ? rfp->within.parent : NULL;
 
 	  case vpiIndex:
-	    return rfp->is_netarray ? rfp->id.index : 0;
+	    return rfp->is_netarray ? rfp->id.index : NULL;
 
 	  case vpiScope:
 	    return vpip_scope(rfp);
@@ -107,7 +107,7 @@ static vpiHandle real_var_iterate(int code, vpiHandle ref)
       assert(rfp);
 
       if (code == vpiIndex) {
-	    return rfp->is_netarray ? rfp->id.index->vpi_iterate(code) : 0;
+	    return rfp->is_netarray ? rfp->id.index->vpi_iterate(code) : NULL;
       }
 
       return 0;
@@ -183,7 +183,7 @@ static vpiHandle vpip_make_real_(__vpiScope*scope, const char*name,
 {
       struct __vpiRealVar*obj = new __vpiRealVar;
 
-      obj->id.name = name ? vpip_name_string(name) : 0;
+      obj->id.name = name ? vpip_name_string(name) : NULL;
       obj->is_netarray = 0;
       obj->is_wire = is_wire;
       obj->net = net;
diff --git a/vvp/vpi_signal.cc b/vvp/vpi_signal.cc
index 7dc30f430..6ed41455f 100644
--- a/vvp/vpi_signal.cc
+++ b/vvp/vpi_signal.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2020 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -639,10 +639,10 @@ static vpiHandle signal_get_handle(int code, vpiHandle ref)
       switch (code) {
 
 	  case vpiParent:
-	    return rfp->is_netarray? rfp->within.parent : 0;
+	    return rfp->is_netarray? rfp->within.parent : NULL;
 
 	  case vpiIndex:
-	    return rfp->is_netarray? rfp->id.index : 0;
+	    return rfp->is_netarray? rfp->id.index : NULL;
 
 	  case vpiLeftRange:
 	    return &rfp->msb;
@@ -665,7 +665,7 @@ static vpiHandle signal_iterate(int code, vpiHandle ref)
       assert(rfp);
 
       if (code == vpiIndex) {
-	    return rfp->is_netarray ? rfp->id.index->vpi_iterate(code) : 0;
+	    return rfp->is_netarray ? rfp->id.index->vpi_iterate(code) : NULL;
       }
 
       return 0;
@@ -1266,7 +1266,7 @@ static vpiHandle fill_in_net4(struct __vpiSignal*obj, __vpiScope*scope,
 			      const char*name, int msb, int lsb,
 			      bool signed_flag, vvp_net_t*node)
 {
-      obj->id.name = name? vpip_name_string(name) : 0;
+      obj->id.name = name? vpip_name_string(name) : NULL;
       obj->msb = __vpiDecConst(msb);
       obj->lsb = __vpiDecConst(lsb);
       obj->signed_flag = signed_flag? 1 : 0;
diff --git a/vvp/vpi_string.cc b/vvp/vpi_string.cc
index b0fbe330c..7ae1d95cd 100644
--- a/vvp/vpi_string.cc
+++ b/vvp/vpi_string.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2015 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2012-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -92,7 +92,7 @@ vpiHandle __vpiStringVar::vpi_put_value(p_vpi_value val, int)
 vpiHandle vpip_make_string_var(const char*name, vvp_net_t*net)
 {
       __vpiScope*scope = vpip_peek_current_scope();
-      const char*use_name = name ? vpip_name_string(name) : 0;
+      const char*use_name = name ? vpip_name_string(name) : NULL;
 
       __vpiStringVar*obj = new __vpiStringVar(scope, use_name, net);
 
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index 93e368619..135b20ea9 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2001-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -3204,7 +3204,7 @@ bool of_FLAG_SET_IMM(vthread_t thr, vvp_code_t cp)
       assert(flag < vthread_s::FLAGS_COUNT);
       assert(vali >= 0 && vali < 4);
 
-      static vvp_bit4_t map_bit[4] = {BIT4_0, BIT4_1, BIT4_Z, BIT4_X};
+      static const vvp_bit4_t map_bit[4] = {BIT4_0, BIT4_1, BIT4_Z, BIT4_X};
       thr->flags[flag] = map_bit[vali];
       return true;
 }
@@ -5162,12 +5162,12 @@ inline void push_value(vthread_t thr, double value, unsigned)
       thr->push_real(value);
 }
 
-inline void push_value(vthread_t thr, string value, unsigned)
+inline void push_value(vthread_t thr, const string&value, unsigned)
 {
       thr->push_str(value);
 }
 
-inline void push_value(vthread_t thr, vvp_vector4_t value, unsigned wid)
+inline void push_value(vthread_t thr, const vvp_vector4_t&value, unsigned wid)
 {
       assert(wid == value.size());
       thr->push_vec4(value);
@@ -5357,7 +5357,7 @@ static void poke_val(vthread_t fun_thr, unsigned depth, double val)
       fun_thr->parent->poke_real(depth, val);
 }
 
-static void poke_val(vthread_t fun_thr, unsigned depth, string val)
+static void poke_val(vthread_t fun_thr, unsigned depth, const string&val)
 {
       fun_thr->parent->poke_str(depth, val);
 }
diff --git a/vvp/vvp_island.cc b/vvp/vvp_island.cc
index 3c2de115b..3bc48268f 100644
--- a/vvp/vvp_island.cc
+++ b/vvp/vvp_island.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2008-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -34,7 +34,9 @@
 
 using namespace std;
 
+#ifdef CHECK_WITH_VALGRIND
 static bool at_EOS = false;
+#endif
 
 void island_send_value(vvp_net_t*net, const vvp_vector8_t&val)
 {
@@ -61,7 +63,9 @@ vvp_island::vvp_island()
 vvp_island::~vvp_island()
 {
 	// We can only delete islands at the end of simulation.
+#ifdef CHECK_WITH_VALGRIND
       if (!at_EOS) assert(0);
+#endif
 
       while (branches_) {
 	    vvp_island_branch *next_br = branches_->next_branch;
diff --git a/vvp/words.cc b/vvp/words.cc
index 80977b029..c8efb65fb 100644
--- a/vvp/words.cc
+++ b/vvp/words.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2003-2022 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -373,7 +373,7 @@ static void __compile_net(char*label,
 			  int vpi_type_code, bool signed_flag, bool local_flag,
 			  unsigned argc, struct symb_s*argv)
 {
-      vvp_array_t array = array_label? array_find(array_label) : 0;
+      vvp_array_t array = array_label? array_find(array_label) : NULL;
       assert(array_label ? array!=0 : true);
 
       free(array_label);
@@ -503,7 +503,7 @@ static void __compile_real(char*label, char*name,
                            unsigned argc, struct symb_s*argv)
 {
       assert(msb == 0 && lsb == 0);
-      vvp_array_t array = array_label ? array_find(array_label) : 0;
+      vvp_array_t array = array_label ? array_find(array_label) : NULL;
       assert(array_label ? array!=0 : true);
 
       free(array_label);