diff --git a/LineInfo.h b/LineInfo.h
new file mode 100644
index 000000000..81c07b834
--- /dev/null
+++ b/LineInfo.h
@@ -0,0 +1,60 @@
+#ifndef __LineInfo_H
+#define __LineInfo_H
+/*
+ * Copyright (c) 1999 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
+ *    General Public License as published by the Free Software
+ *    Foundation; either version 2 of the License, or (at your option)
+ *    any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+#if !defined(WINNT)
+#ident "$Id: LineInfo.h,v 1.1 1999/01/25 05:45:56 steve Exp $"
+#endif
+
+# include  <cstdio>
+
+class LineInfo {
+    public:
+      LineInfo() : lineno_(0) { }
+
+      string get_line() const
+	    { char buf[8];
+	      sprintf(buf, "%u", lineno_);
+	      return file_ + ":" + buf;
+	    }
+
+      void set_file(const string&f) { file_ = f; }
+      void set_lineno(unsigned n) { lineno_ = n; }
+
+    private:
+      string file_;
+      unsigned lineno_;
+};
+
+/*
+ * $Log: LineInfo.h,v $
+ * Revision 1.1  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
+ */
+#endif
diff --git a/Module.h b/Module.h
index fb45f56dc..92372226d 100644
--- a/Module.h
+++ b/Module.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: Module.h,v 1.1 1998/11/03 23:28:52 steve Exp $"
+#ident "$Id: Module.h,v 1.2 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  <list>
@@ -57,7 +57,7 @@ class Module {
       const list<PGate*>& get_gates() const { return gates_; }
       const list<PProcess*>& get_behaviors() const { return behaviors_; }
 
-      void elaborate(Design*, const string&path) const;
+      bool elaborate(Design*, const string&path) const;
 
     private:
       const string name_;
@@ -74,6 +74,18 @@ class Module {
 
 /*
  * $Log: Module.h,v $
+ * Revision 1.2  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.1  1998/11/03 23:28:52  steve
  *  Introduce verilog to CVS.
  *
diff --git a/PGate.h b/PGate.h
index 0ea434929..c292daf40 100644
--- a/PGate.h
+++ b/PGate.h
@@ -19,10 +19,11 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: PGate.h,v 1.2 1998/12/01 00:42:13 steve Exp $"
+#ident "$Id: PGate.h,v 1.3 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  <vector>
+# include  "LineInfo.h"
 class PExpr;
 class PUdp;
 class Design;
@@ -36,7 +37,7 @@ class Design;
  * step will need to convert expressions to a network of gates in
  * order to elaborate expression inputs, but that can easily be done.
  */
-class PGate {
+class PGate : public LineInfo {
       
     public:
       explicit PGate(const string&name, const vector<PExpr*>&pins, long del)
@@ -135,6 +136,18 @@ class PGModule  : public PGate {
 
 /*
  * $Log: PGate.h,v $
+ * Revision 1.3  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.2  1998/12/01 00:42:13  steve
  *  Elaborate UDP devices,
  *  Support UDP type attributes, and
diff --git a/Statement.cc b/Statement.cc
index 3ff826326..390945175 100644
--- a/Statement.cc
+++ b/Statement.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: Statement.cc,v 1.3 1998/11/11 03:13:04 steve Exp $"
+#ident "$Id: Statement.cc,v 1.4 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  "Statement.h"
@@ -64,6 +64,10 @@ PCondit::~PCondit()
       delete else_;
 }
 
+PProcess::~PProcess()
+{
+      delete statement_;
+}
 
 PWhile::~PWhile()
 {
@@ -73,6 +77,18 @@ PWhile::~PWhile()
 
 /*
  * $Log: Statement.cc,v $
+ * Revision 1.4  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.3  1998/11/11 03:13:04  steve
  *  Handle while loops.
  *
diff --git a/Statement.h b/Statement.h
index eb9b79656..cb680aaf4 100644
--- a/Statement.h
+++ b/Statement.h
@@ -19,12 +19,13 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: Statement.h,v 1.4 1998/11/11 03:13:04 steve Exp $"
+#ident "$Id: Statement.h,v 1.5 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  <string>
 # include  <list>
 # include  "netlist.h"
+# include  "LineInfo.h"
 class PExpr;
 class Statement;
 
@@ -34,7 +35,7 @@ class Statement;
  * pointer to the single statement that is the process. A module may
  * have several concurrent processes.
  */
-class PProcess {
+class PProcess : public LineInfo {
 
     public:
       enum Type { PR_INITIAL, PR_ALWAYS };
@@ -42,6 +43,8 @@ class PProcess {
       PProcess(Type t, Statement*st)
       : type_(t), statement_(st) { }
 
+      virtual ~PProcess();
+
       Type type() const { return type_; }
       Statement*statement() { return statement_; }
 
@@ -57,7 +60,7 @@ class PProcess {
  * fact, the Statement class is abstract and represents all the
  * possible kinds of statements that exist in Verilog.
  */
-class Statement {
+class Statement : public LineInfo {
 
     public:
       Statement() { }
@@ -245,6 +248,18 @@ class PWhile  : public Statement {
 
 /*
  * $Log: Statement.h,v $
+ * Revision 1.5  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.4  1998/11/11 03:13:04  steve
  *  Handle while loops.
  *
diff --git a/elaborate.cc b/elaborate.cc
index 3916fc643..631fea71c 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: elaborate.cc,v 1.10 1998/12/14 02:01:34 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.11 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 /*
@@ -221,6 +221,14 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, const string&path) const
 	// Now connect the ports of the newly elaborated designs to
 	// the expressions that are the instantiation parameters.
 
+      if (pin_count() != rmod->ports.size()) {
+	    cerr << get_line() << ": Wrong number "
+		  "of parameters. Expecting " << rmod->ports.size() <<
+		  ", got " << pin_count() << "."
+		 << endl;
+	    return;
+      }
+
       assert(pin_count() == rmod->ports.size());
 
       for (unsigned idx = 0 ;  idx < pin_count() ;  idx += 1) {
@@ -240,12 +248,22 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, const string&path) const
 
 	    assert(prt->pin_count() == sig->pin_count());
 	    switch (prt->port_type()) {
+		    // INPUT and OUTPUT ports are directional. Handle
+		    // them like assignments.
 		case NetNet::PINPUT:
 		  do_assign(des, path, prt, sig);
 		  break;
 		case NetNet::POUTPUT:
 		  do_assign(des, path, sig, prt);
 		  break;
+
+		    // INOUT ports are like terminal posts. Just
+		    // connect the inside and the outside nets
+		    // together.
+		case NetNet::PINOUT:
+		  for (unsigned p = 0 ;  p < sig->pin_count() ;  p += 1)
+			connect(prt->pin(p), sig->pin(p));
+		  break;
 		default:
 		  assert(0);
 	    }
@@ -569,10 +587,17 @@ NetProc* PAssign::elaborate(Design*des, const string&path) const
 {
       NetNet*reg = des->find_signal(path+"."+lval());
       if (reg == 0) {
-	    cerr << "Could not match signal: " << lval() << endl;
-	    return new NetProc;
+	    cerr << get_line() << ": Could not match signal: " <<
+		  lval() << endl;
+	    return 0;
       }
       assert(reg);
+
+      if (reg->type() != NetNet::REG) {
+	    cerr << get_line() << ": " << lval() << " is not a register."
+		 << endl;
+	    return 0;
+      }
       assert(reg->type() == NetNet::REG);
       assert(expr_);
 
@@ -585,11 +610,29 @@ NetProc* PAssign::elaborate(Design*des, const string&path) const
       return cur;
 }
 
+/*
+ * This is the elaboration method for a begin-end block. Try to
+ * elaborate the entire block, even if it fails somewhere. This way I
+ * get all the error messages out of it. Then, if I detected a failure
+ * then pass the failure up.
+ */
 NetProc* PBlock::elaborate(Design*des, const string&path) const
 {
       NetBlock*cur = new NetBlock(NetBlock::SEQU);
+      bool fail_flag = false;
+
       for (unsigned idx = 0 ;  idx < size() ;  idx += 1) {
-	    cur->append(stat(idx)->elaborate(des, path));
+	    NetProc*tmp = stat(idx)->elaborate(des, path);
+	    if (tmp == 0) {
+		  fail_flag = true;
+		  continue;
+	    }
+	    cur->append(tmp);
+      }
+
+      if (fail_flag) {
+	    delete cur;
+	    cur = 0;
       }
 
       return cur;
@@ -635,14 +678,18 @@ NetProc* PDelayStatement::elaborate(Design*des, const string&path) const
 NetProc* PEventStatement::elaborate(Design*des, const string&path) const
 {
       NetProc*enet = statement_->elaborate(des, path);
+      if (enet == 0)
+	    return 0;
+
       NetPEvent*ev = new NetPEvent(des->local_symbol(path), type_, enet);
 
       NetNet*expr = expr_->elaborate_net(des, path);
       if (expr == 0) {
-	    cerr << "Failed to elaborate expression: ";
+	    cerr << get_line() << ": Failed to elaborate expression: ";
 	    expr_->dump(cerr);
 	    cerr << endl;
-	    exit(1);
+	    delete ev;
+	    return 0;
       }
       assert(expr);
       connect(ev->pin(0), expr->pin(0));
@@ -695,8 +742,10 @@ NetProc* PWhile::elaborate(Design*des, const string&path) const
       return loop;
 }
 
-void Module::elaborate(Design*des, const string&path) const
+bool Module::elaborate(Design*des, const string&path) const
 {
+      bool result_flag = true;
+
 	// Get all the explicitly declared wires of the module and
 	// start the signals list with them.
       const list<PWire*>&wl = get_wires();
@@ -728,6 +777,13 @@ void Module::elaborate(Design*des, const string&path) const
 		 ; st ++ ) {
 
 	    NetProc*cur = (*st)->statement()->elaborate(des, path);
+	    if (cur == 0) {
+		  cerr << (*st)->get_line() << ": Elaboration "
+			"failed for this process." << endl;
+		  result_flag = false;
+		  continue;
+	    }
+
 	    NetProcTop*top;
 	    switch ((*st)->type()) {
 		case PProcess::PR_INITIAL:
@@ -740,6 +796,8 @@ void Module::elaborate(Design*des, const string&path) const
 
 	    des->add_process(top);
       }
+
+      return result_flag;
 }
 
 Design* elaborate(const map<string,Module*>&modules,
@@ -759,16 +817,32 @@ Design* elaborate(const map<string,Module*>&modules,
 
       modlist = &modules;
       udplist = &primitives;
-      rmod->elaborate(des, root);
+      bool rc = rmod->elaborate(des, root);
       modlist = 0;
       udplist = 0;
 
+      if (rc == false) {
+	    delete des;
+	    des = 0;
+      }
       return des;
 }
 
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.11  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.10  1998/12/14 02:01:34  steve
  *  Fully elaborate Sequential UDP behavior.
  *
diff --git a/parse.y b/parse.y
index a06f53c4d..9ac54dda9 100644
--- a/parse.y
+++ b/parse.y
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: parse.y,v 1.10 1998/12/18 05:16:25 steve Exp $"
+#ident "$Id: parse.y,v 1.11 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  "parse_misc.h"
@@ -271,6 +271,8 @@ gate_instance
 		{ lgate*tmp = new lgate;
 		  tmp->name = *$1;
 		  tmp->parms = $3;
+		  tmp->file  = @1.text;
+		  tmp->lineno = @1.first_line;
 		  delete $1;
 		  $$ = tmp;
 		}
@@ -278,6 +280,8 @@ gate_instance
 		{ lgate*tmp = new lgate;
 		  tmp->name = "";
 		  tmp->parms = $2;
+		  tmp->file  = @1.text;
+		  tmp->lineno = @1.first_line;
 		  $$ = tmp;
 		}
 	;
@@ -446,10 +450,14 @@ module_item
 		  delete $3;
 		}
 	| K_always statement
-		{ pform_make_behavior(PProcess::PR_ALWAYS, $2);
+		{ PProcess*tmp = pform_make_behavior(PProcess::PR_ALWAYS, $2);
+		  tmp->set_file(@1.text);
+		  tmp->set_lineno(@1.first_line);
 		}
 	| K_initial statement
-		{ pform_make_behavior(PProcess::PR_INITIAL, $2);
+		{ PProcess*tmp = pform_make_behavior(PProcess::PR_INITIAL, $2);
+		  tmp->set_file(@1.text);
+		  tmp->set_lineno(@1.first_line);
 		}
 	| KK_attribute '(' IDENTIFIER ',' STRING ',' STRING ')' ';'
 		{ pform_set_attrib(*$3, *$5, *$7);
@@ -592,7 +600,10 @@ statement
 		  $$ = tmp;
 		}
 	| lvalue '=' expression ';'
-		{ $$ = pform_make_assignment($1, $3);
+		{ Statement*tmp = pform_make_assignment($1, $3);
+		  tmp->set_file(@1.text);
+		  tmp->set_lineno(@1.first_line);
+		  $$ = tmp;
 		}
 	| lvalue K_LE expression ';'
 		{ $$ = pform_make_assignment($1, $3);
@@ -699,6 +710,8 @@ udp_initial
 	: K_initial IDENTIFIER '=' NUMBER ';'
 		{ PExpr*etmp = new PENumber($4);
 		  PAssign*atmp = new PAssign(*$2, etmp);
+		  atmp->set_file(@2.text);
+		  atmp->set_lineno(@2.first_line);
 		  delete $2;
 		  $$ = atmp;
 		}
diff --git a/pform.cc b/pform.cc
index 07c4c8a31..1893cf76f 100644
--- a/pform.cc
+++ b/pform.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: pform.cc,v 1.7 1998/12/09 04:02:47 steve Exp $"
+#ident "$Id: pform.cc,v 1.8 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  "pform.h"
@@ -27,6 +27,7 @@
 # include  <map>
 # include  <assert.h>
 # include  <typeinfo>
+# include  <strstream>
 
 /*
  * The lexor accesses the vl_* variables.
@@ -261,9 +262,12 @@ void pform_makegates(PGBuiltin::Type type,
 
 void pform_make_modgate(const string&type,
 			const string&name,
-			const vector<PExpr*>&wires)
+			const vector<PExpr*>&wires,
+			const string&fn, unsigned ln)
 {
       PGate*cur = new PGModule(type, name, wires);
+      cur->set_file(fn);
+      cur->set_lineno(ln);
       cur_module->add_gate(cur);
 }
 
@@ -281,7 +285,7 @@ void pform_make_modgates(const string&type, list<lgate>*gates)
 		  wires[idx] = ep;
 	    }
 
-	    pform_make_modgate(type, cur.name, wires);
+	    pform_make_modgate(type, cur.name, wires, cur.file, cur.lineno);
       }
 
       delete gates;
@@ -311,9 +315,11 @@ void pform_makewire(const string&name, NetNet::Type type)
 {
       PWire*cur = cur_module->get_wire(name);
       if (cur) {
-	    if (cur->type != NetNet::IMPLICIT)
-		  VLerror("Extra definition of wire.");
-
+	    if (cur->type != NetNet::IMPLICIT) {
+		  strstream msg;
+		  msg << "Duplicate definition of " << name << ".";
+		  VLerror(msg.str());
+	    }
 	    cur->type = type;
 	    return;
       }
@@ -433,10 +439,11 @@ list<PWire*>* pform_make_udp_input_ports(list<string>*names)
       return out;
 }
 
-void pform_make_behavior(PProcess::Type type, Statement*st)
+PProcess* pform_make_behavior(PProcess::Type type, Statement*st)
 {
       PProcess*pp = new PProcess(type, st);
       cur_module->add_behavior(pp);
+      return pp;
 }
 
 Statement* pform_make_block(PBlock::BL_TYPE type, list<Statement*>*sl)
@@ -493,6 +500,18 @@ int pform_parse(const char*path, map<string,Module*>&modules,
 
 /*
  * $Log: pform.cc,v $
+ * Revision 1.8  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.7  1998/12/09 04:02:47  steve
  *  Support the include directive.
  *
diff --git a/pform.h b/pform.h
index d83337e0a..3906ea516 100644
--- a/pform.h
+++ b/pform.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: pform.h,v 1.5 1998/12/09 04:02:47 steve Exp $"
+#ident "$Id: pform.h,v 1.6 1999/01/25 05:45:56 steve Exp $"
 #endif
 
 # include  "netlist.h"
@@ -63,8 +63,13 @@ class PExpr;
  */
 
 struct lgate {
+      lgate() : parms(0), lineno(0) { }
+
       string name;
       list<PExpr*>*parms;
+
+      string file;
+      unsigned lineno;
 };
 
 
@@ -94,7 +99,7 @@ extern void pform_set_attrib(const string&name, const string&key,
 			     const string&value);
 extern void pform_set_type_attrib(const string&name, const string&key,
 				  const string&value);
-extern void pform_make_behavior(PProcess::Type, Statement*);
+extern PProcess*  pform_make_behavior(PProcess::Type, Statement*);
 extern Statement* pform_make_block(PBlock::BL_TYPE, list<Statement*>*);
 extern Statement* pform_make_assignment(string*t, PExpr*e);
 extern Statement* pform_make_calltask(string*t, list<PExpr*>* =0);
@@ -132,6 +137,18 @@ extern void pform_dump(ostream&out, Module*mod);
 
 /*
  * $Log: pform.h,v $
+ * Revision 1.6  1999/01/25 05:45:56  steve
+ *  Add the LineInfo class to carry the source file
+ *  location of things. PGate, Statement and PProcess.
+ *
+ *  elaborate handles module parameter mismatches,
+ *  missing or incorrect lvalues for procedural
+ *  assignment, and errors are propogated to the
+ *  top of the elaboration call tree.
+ *
+ *  Attach line numbers to processes, gates and
+ *  assignment statements.
+ *
  * Revision 1.5  1998/12/09 04:02:47  steve
  *  Support the include directive.
  *