diff --git a/Attrib.cc b/Attrib.cc
index bb3488b5a..543768d2b 100644
--- a/Attrib.cc
+++ b/Attrib.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: Attrib.cc,v 1.5 2002/08/12 01:34:58 steve Exp $"
+#ident "$Id: Attrib.cc,v 1.6 2004/02/20 18:53:33 steve Exp $"
 #endif
 
 # include "config.h"
@@ -36,25 +36,8 @@ Attrib::~Attrib()
       delete[] list_;
 }
 
-#if 0
-void Attrib::copy_attributes(const map<string,verinum>&attr)
-{
-      assert(list_ == 0);
 
-      nlist_ = attr.size();
-      list_ = new cell_[nlist_];
-
-      map<string,verinum>::const_iterator idx;
-      unsigned jdx;
-      for (idx = attr.begin(), jdx = 0 ;  idx != attr.end() ;  idx ++, jdx++) {
-	    struct cell_*tmp = list_ + jdx;
-	    tmp->key = (*idx).first;
-	    tmp->val = (*idx).second;
-      }
-}
-#endif
-
-const verinum& Attrib::attribute(const string&key) const
+const verinum& Attrib::attribute(perm_string key) const
 {
       for (unsigned idx = 0 ;  idx < nlist_ ;  idx += 1) {
 
@@ -66,7 +49,7 @@ const verinum& Attrib::attribute(const string&key) const
       return null;
 }
 
-void Attrib::attribute(const string&key, const verinum&value)
+void Attrib::attribute(perm_string key, const verinum&value)
 {
       unsigned idx;
 
@@ -108,10 +91,10 @@ unsigned Attrib::attr_cnt() const
       return nlist_;
 }
 
-const char* Attrib::attr_key(unsigned idx) const
+perm_string Attrib::attr_key(unsigned idx) const
 {
       assert(idx < nlist_);
-      return list_[idx].key.c_str();
+      return list_[idx].key;
 }
 
 const verinum& Attrib::attr_value(unsigned idx) const
@@ -123,6 +106,9 @@ const verinum& Attrib::attr_value(unsigned idx) const
 
 /*
  * $Log: Attrib.cc,v $
+ * Revision 1.6  2004/02/20 18:53:33  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.5  2002/08/12 01:34:58  steve
  *  conditional ident string using autoconfig.
  *
diff --git a/Attrib.h b/Attrib.h
index ef7ca77d5..cdec41378 100644
--- a/Attrib.h
+++ b/Attrib.h
@@ -19,10 +19,10 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: Attrib.h,v 1.4 2002/08/12 01:34:58 steve Exp $"
+#ident "$Id: Attrib.h,v 1.5 2004/02/20 18:53:33 steve Exp $"
 #endif
 
-# include  <string>
+# include  "StringHeap.h"
 # include  "verinum.h"
 
 /*
@@ -35,20 +35,20 @@ class Attrib {
       Attrib();
       ~Attrib();
 
-      const verinum&attribute(const string&key) const;
-      void attribute(const string&key, const verinum&value);
+      const verinum&attribute(perm_string key) const;
+      void attribute(perm_string key, const verinum&value);
       bool has_compat_attributes(const Attrib&that) const;
 
 
 	/* Provide a means of iterating over the entries in the map. */
       unsigned       attr_cnt() const;
-      const char*    attr_key(unsigned idx) const;
+      perm_string    attr_key(unsigned idx) const;
       const verinum& attr_value(unsigned idx) const;
 
 
     private:
       struct cell_ {
-	    string  key;
+	    perm_string  key;
 	    verinum val;
       };
 
@@ -62,6 +62,9 @@ class Attrib {
 
 /*
  * $Log: Attrib.h,v $
+ * Revision 1.5  2004/02/20 18:53:33  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.4  2002/08/12 01:34:58  steve
  *  conditional ident string using autoconfig.
  *
diff --git a/Module.h b/Module.h
index df288d22b..543b2f30e 100644
--- a/Module.h
+++ b/Module.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: Module.h,v 1.34 2004/02/20 06:22:56 steve Exp $"
+#ident "$Id: Module.h,v 1.35 2004/02/20 18:53:33 steve Exp $"
 #endif
 
 # include  <list>
@@ -110,7 +110,7 @@ class Module : public LineInfo {
 	/* Keep a table of datum variables declared in the module. */
       map<hname_t,PData*>datum;
 
-      map<string,PExpr*> attributes;
+      map<perm_string,PExpr*> attributes;
 
 	/* These are the timescale for this module. The default is
 	   set by the `timescale directive. */
@@ -166,6 +166,9 @@ class Module : public LineInfo {
 
 /*
  * $Log: Module.h,v $
+ * Revision 1.35  2004/02/20 18:53:33  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.34  2004/02/20 06:22:56  steve
  *  parameter keys are per_strings.
  *
diff --git a/PGate.h b/PGate.h
index 2cdae4665..803191c58 100644
--- a/PGate.h
+++ b/PGate.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: PGate.h,v 1.26 2004/02/18 17:11:54 steve Exp $"
+#ident "$Id: PGate.h,v 1.27 2004/02/20 18:53:33 steve Exp $"
 #endif
 
 # include  "svector.h"
@@ -80,7 +80,7 @@ class PGate : public LineInfo {
       void strength0(strength_t);
       void strength1(strength_t);
 
-      map<string,PExpr*> attributes;
+      map<perm_string,PExpr*> attributes;
 
       virtual void dump(ostream&out) const;
       virtual void elaborate(Design*des, NetScope*scope) const;
@@ -227,6 +227,9 @@ class PGModule  : public PGate {
 
 /*
  * $Log: PGate.h,v $
+ * Revision 1.27  2004/02/20 18:53:33  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.26  2004/02/18 17:11:54  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/PWire.h b/PWire.h
index b486ab403..350c08047 100644
--- a/PWire.h
+++ b/PWire.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: PWire.h,v 1.16 2003/01/30 16:23:07 steve Exp $"
+#ident "$Id: PWire.h,v 1.17 2004/02/20 18:53:33 steve Exp $"
 #endif
 
 # include  "netlist.h"
@@ -69,7 +69,7 @@ class PWire : public LineInfo {
 
       void set_memory_idx(PExpr*ldx, PExpr*rdx);
 
-      map<string,PExpr*> attributes;
+      map<perm_string,PExpr*> attributes;
 
 	// Write myself to the specified stream.
       void dump(ostream&out) const;
@@ -100,6 +100,9 @@ class PWire : public LineInfo {
 
 /*
  * $Log: PWire.h,v $
+ * Revision 1.17  2004/02/20 18:53:33  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.16  2003/01/30 16:23:07  steve
  *  Spelling fixes.
  *
diff --git a/Statement.h b/Statement.h
index a3352d42b..85b845add 100644
--- a/Statement.h
+++ b/Statement.h
@@ -19,11 +19,12 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: Statement.h,v 1.39 2004/02/18 17:11:54 steve Exp $"
+#ident "$Id: Statement.h,v 1.40 2004/02/20 18:53:33 steve Exp $"
 #endif
 
 # include  <string>
 # include  "svector.h"
+# include  "StringHeap.h"
 # include  "PDelays.h"
 # include  "PExpr.h"
 # include  "HName.h"
@@ -56,7 +57,7 @@ class PProcess : public LineInfo {
       Type type() const { return type_; }
       Statement*statement() { return statement_; }
 
-      map<string,PExpr*> attributes;
+      map<perm_string,PExpr*> attributes;
 
       virtual void dump(ostream&out, unsigned ind) const;
 
@@ -455,6 +456,9 @@ class PWhile  : public Statement {
 
 /*
  * $Log: Statement.h,v $
+ * Revision 1.40  2004/02/20 18:53:33  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.39  2004/02/18 17:11:54  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/cprop.cc b/cprop.cc
index 0eb3e0ba4..ab2ac3073 100644
--- a/cprop.cc
+++ b/cprop.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: cprop.cc,v 1.46 2003/11/08 17:53:34 steve Exp $"
+#ident "$Id: cprop.cc,v 1.47 2004/02/20 18:53:34 steve Exp $"
 #endif
 
 # include "config.h"
@@ -56,7 +56,7 @@ void cprop_functor::signal(Design*des, NetNet*obj)
 void cprop_functor::lpm_add_sub(Design*des, NetAddSub*obj)
 {
 	// For now, only additions are handled.
-      if (obj->attribute("LPM_Direction") != verinum("ADD"))
+      if (obj->attribute(perm_string::literal("LPM_Direction")) != verinum("ADD"))
 	    return;
 
 	// If the low bit on the A side is 0, then eliminate it from
@@ -1038,6 +1038,9 @@ void cprop(Design*des)
 
 /*
  * $Log: cprop.cc,v $
+ * Revision 1.47  2004/02/20 18:53:34  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.46  2003/11/08 17:53:34  steve
  *  Do not remove constants accessible to VPI.
  *
diff --git a/elab_net.cc b/elab_net.cc
index 0b4e766f2..c281fd4dd 100644
--- a/elab_net.cc
+++ b/elab_net.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elab_net.cc,v 1.124 2004/02/18 17:11:54 steve Exp $"
+#ident "$Id: elab_net.cc,v 1.125 2004/02/20 18:53:34 steve Exp $"
 #endif
 
 # include "config.h"
@@ -246,10 +246,10 @@ NetNet* PEBinary::elaborate_net_add_(Design*des, NetScope*scope,
 
       switch (op_) {
 	  case '+':
-	    gate->attribute("LPM_Direction", verinum("ADD"));
+	    gate->attribute(perm_string::literal("LPM_Direction"), verinum("ADD"));
 	    break;
 	  case '-':
-	    gate->attribute("LPM_Direction", verinum("SUB"));
+	    gate->attribute(perm_string::literal("LPM_Direction"), verinum("SUB"));
 	    break;
       }
 
@@ -2386,7 +2386,7 @@ NetNet* PEUnary::elaborate_net(Design*des, NetScope*scope,
 		default:
 		  NetAddSub*sub = new NetAddSub(scope, scope->local_symbol(),
 						sig->pin_count());
-		  sub->attribute("LPM_Direction", verinum("SUB"));
+		  sub->attribute(perm_string::literal("LPM_Direction"), verinum("SUB"));
 
 		  des->add_node(sub);
 
@@ -2426,6 +2426,9 @@ NetNet* PEUnary::elaborate_net(Design*des, NetScope*scope,
 
 /*
  * $Log: elab_net.cc,v $
+ * Revision 1.125  2004/02/20 18:53:34  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.124  2004/02/18 17:11:54  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/elaborate.cc b/elaborate.cc
index 2fa3d11a6..575a66dd5 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elaborate.cc,v 1.296 2004/02/18 17:11:55 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.297 2004/02/20 18:53:34 steve Exp $"
 #endif
 
 # include "config.h"
@@ -2516,7 +2516,8 @@ bool Module::elaborate(Design*des, NetScope*scope) const
 		  if (! anyedge_test)
 			break;
 
-		  top->attribute("_ivl_schedule_push", verinum(1));
+		  top->attribute(perm_string::literal("_ivl_schedule_push"),
+				 verinum(1));
 	    } while (0);
 
       }
@@ -2626,6 +2627,9 @@ Design* elaborate(list<perm_string>roots)
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.297  2004/02/20 18:53:34  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.296  2004/02/18 17:11:55  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/eval_attrib.cc b/eval_attrib.cc
index 94ff0e900..cc6943d40 100644
--- a/eval_attrib.cc
+++ b/eval_attrib.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2002-2004 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
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: eval_attrib.cc,v 1.6 2003/01/27 05:09:17 steve Exp $"
+#ident "$Id: eval_attrib.cc,v 1.7 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include  "config.h"
@@ -33,7 +33,7 @@
  * for passing to netlist devices.
  */
 
-attrib_list_t* evaluate_attributes(const map<string,PExpr*>&att,
+attrib_list_t* evaluate_attributes(const map<perm_string,PExpr*>&att,
 				   unsigned&natt,
 				   const Design*des,
 				   const NetScope*scope)
@@ -46,7 +46,7 @@ attrib_list_t* evaluate_attributes(const map<string,PExpr*>&att,
 
       unsigned idx = 0;
 
-      typedef map<string,PExpr*>::const_iterator iter_t;
+      typedef map<perm_string,PExpr*>::const_iterator iter_t;
       for (iter_t cur = att.begin() ;  cur != att.end() ;  cur ++, idx++) {
 	    table[idx].key = (*cur).first;
 	    PExpr*exp = (*cur).second;
@@ -74,6 +74,9 @@ attrib_list_t* evaluate_attributes(const map<string,PExpr*>&att,
 
 /*
  * $Log: eval_attrib.cc,v $
+ * Revision 1.7  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.6  2003/01/27 05:09:17  steve
  *  Spelling fixes.
  *
diff --git a/expr_synth.cc b/expr_synth.cc
index 51c0281c6..6c47f5a67 100644
--- a/expr_synth.cc
+++ b/expr_synth.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: expr_synth.cc,v 1.54 2004/02/18 17:11:56 steve Exp $"
+#ident "$Id: expr_synth.cc,v 1.55 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -69,10 +69,10 @@ NetNet* NetEBAdd::synthesize(Design*des)
 
       switch (op()) {
 	  case '+':
-	    adder->attribute("LPM_Direction", verinum("ADD"));
+	    adder->attribute(perm_string::literal("LPM_Direction"), verinum("ADD"));
 	    break;
 	  case '-':
-	    adder->attribute("LPM_Direction", verinum("SUB"));
+	    adder->attribute(perm_string::literal("LPM_Direction"), verinum("SUB"));
 	    break;
       }
 
@@ -828,6 +828,9 @@ NetNet* NetESignal::synthesize(Design*des)
 
 /*
  * $Log: expr_synth.cc,v $
+ * Revision 1.55  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.54  2004/02/18 17:11:56  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/netmisc.cc b/netmisc.cc
index fc20a1e21..6de900652 100644
--- a/netmisc.cc
+++ b/netmisc.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: netmisc.cc,v 1.7 2004/02/18 17:11:57 steve Exp $"
+#ident "$Id: netmisc.cc,v 1.8 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -62,9 +62,9 @@ NetNet* add_to_net(Design*des, NetNet*sig, long val)
 	    connect(res->pin(idx), add->pin_Result(idx));
 
       if (val < 0)
-	    add->attribute("LPM_Direction", verinum("SUB"));
+	    add->attribute(perm_string::literal("LPM_Direction"), verinum("SUB"));
       else
-	    add->attribute("LPM_Direction", verinum("ADD"));
+	    add->attribute(perm_string::literal("LPM_Direction"), verinum("ADD"));
 
       des->add_node(add);
       des->add_node(val_c);
@@ -90,6 +90,9 @@ NetExpr* elab_and_eval(Design*des, NetScope*scope, const PExpr*pe)
 
 /*
  * $Log: netmisc.cc,v $
+ * Revision 1.8  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.7  2004/02/18 17:11:57  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/nodangle.cc b/nodangle.cc
index f3e6ec956..b90eee000 100644
--- a/nodangle.cc
+++ b/nodangle.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: nodangle.cc,v 1.20 2004/01/15 06:04:19 steve Exp $"
+#ident "$Id: nodangle.cc,v 1.21 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -121,7 +121,7 @@ void nodangle_f::signal(Design*des, NetNet*sig)
 
 	/* Can't delete ports of cells. */
       if ((sig->port_type() != NetNet::NOT_A_PORT)
-	  && (sig->scope()->attribute("ivl_synthesis_cell") != verinum()))
+	  && (sig->scope()->attribute(perm_string::literal("ivl_synthesis_cell")) != verinum()))
 	    return;
 
 	/* Check to see if the signal is completely unconnected. If
@@ -205,6 +205,9 @@ void nodangle(Design*des)
 
 /*
  * $Log: nodangle.cc,v $
+ * Revision 1.21  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.20  2004/01/15 06:04:19  steve
  *  Remove duplicate NetEvProbe objects in nodangle.
  *
diff --git a/parse.y b/parse.y
index b70fae5d3..474b96f76 100644
--- a/parse.y
+++ b/parse.y
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: parse.y,v 1.191 2004/02/20 06:22:57 steve Exp $"
+#ident "$Id: parse.y,v 1.192 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -1724,7 +1724,8 @@ module_item
 
 	| KK_attribute '(' IDENTIFIER ',' STRING ',' STRING ')' ';'
 		{ perm_string tmp3 = lex_strings.make($3);
-		  pform_set_attrib(tmp3, $5, $7);
+		  perm_string tmp5 = lex_strings.make($5);
+		  pform_set_attrib(tmp3, tmp5, $7);
 		  delete $3;
 		  delete $5;
 		}
diff --git a/pform.cc b/pform.cc
index 00b681ab8..e91abc4dc 100644
--- a/pform.cc
+++ b/pform.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: pform.cc,v 1.122 2004/02/20 06:22:58 steve Exp $"
+#ident "$Id: pform.cc,v 1.123 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -208,7 +208,7 @@ void pform_startmodule(const char*name, const char*file, unsigned lineno,
       if (attr) {
 	      for (unsigned idx = 0 ;  idx < attr->count() ;  idx += 1) {
 		      named_pexpr_t*tmp = (*attr)[idx];
-		      pform_cur_module->attributes[string(tmp->name)] = tmp->parm;
+		      pform_cur_module->attributes[tmp->name] = tmp->parm;
 	      }
       }
 }
@@ -697,7 +697,7 @@ void pform_makegate(PGBuiltin::Type type,
       if (attr) {
 	    for (unsigned idx = 0 ;  idx < attr->count() ;  idx += 1) {
 		  named_pexpr_t*tmp = (*attr)[idx];
-		  cur->attributes[string(tmp->name)] = tmp->parm;
+		  cur->attributes[tmp->name] = tmp->parm;
 	    }
       }
 
@@ -975,7 +975,7 @@ void pform_module_define_port(const struct vlltype&li,
       if (attr) {
 	      for (unsigned idx = 0 ;  idx < attr->count() ;  idx += 1) {
 		      named_pexpr_t*tmp = (*attr)[idx];
-		      cur->attributes[string(tmp->name)] = tmp->parm;
+		      cur->attributes[tmp->name] = tmp->parm;
 	      }
       }
       pform_cur_module->add_wire(cur);
@@ -1035,7 +1035,7 @@ void pform_makewire(const vlltype&li, const char*nm,
       if (attr) {
 	    for (unsigned idx = 0 ;  idx < attr->count() ;  idx += 1) {
 		  named_pexpr_t*tmp = (*attr)[idx];
-		  cur->attributes[string(tmp->name)] = tmp->parm;
+		  cur->attributes[tmp->name] = tmp->parm;
 	    }
       }
 
@@ -1259,7 +1259,7 @@ void pform_set_function(const char*name, NetNet::Type ntype,
       pform_cur_module->add_function(lex_strings.make(name), func);
 }
 
-void pform_set_attrib(perm_string name, const string&key, char*value)
+void pform_set_attrib(perm_string name, perm_string key, char*value)
 {
       hname_t path (name);
 
@@ -1469,7 +1469,7 @@ PProcess* pform_make_behavior(PProcess::Type type, Statement*st,
       if (attr) {
 	    for (unsigned idx = 0 ;  idx < attr->count() ;  idx += 1) {
 		  named_pexpr_t*tmp = (*attr)[idx];
-		  pp->attributes[string(tmp->name)] = tmp->parm;
+		  pp->attributes[tmp->name] = tmp->parm;
 	    }
 	    delete attr;
       }
@@ -1519,6 +1519,9 @@ int pform_parse(const char*path, FILE*file)
 
 /*
  * $Log: pform.cc,v $
+ * Revision 1.123  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.122  2004/02/20 06:22:58  steve
  *  parameter keys are per_strings.
  *
diff --git a/pform.h b/pform.h
index ab518720f..1fc3afa37 100644
--- a/pform.h
+++ b/pform.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: pform.h,v 1.75 2004/02/20 06:22:58 steve Exp $"
+#ident "$Id: pform.h,v 1.76 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include  "netlist.h"
@@ -202,7 +202,7 @@ extern void pform_set_function(const char*, NetNet::Type,
      $attribute syntax, which can only set string values to
      attributes. The functions keep the value strings that are
      passed in. */
-extern void pform_set_attrib(perm_string name, const string&key,
+extern void pform_set_attrib(perm_string name, perm_string key,
 			     char*value);
 extern void pform_set_type_attrib(perm_string name, const string&key,
 				  char*value);
@@ -283,6 +283,9 @@ extern void pform_dump(ostream&out, Module*mod);
 
 /*
  * $Log: pform.h,v $
+ * Revision 1.76  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.75  2004/02/20 06:22:58  steve
  *  parameter keys are per_strings.
  *
diff --git a/pform_dump.cc b/pform_dump.cc
index 3d9bfcb8d..6a4b2be70 100644
--- a/pform_dump.cc
+++ b/pform_dump.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2000 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1998-2004 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
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: pform_dump.cc,v 1.84 2004/02/20 06:22:58 steve Exp $"
+#ident "$Id: pform_dump.cc,v 1.85 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -252,7 +252,7 @@ void PWire::dump(ostream&out) const
       }
 
       out << ";" << endl;
-      for (map<string,PExpr*>::const_iterator idx = attributes.begin()
+      for (map<perm_string,PExpr*>::const_iterator idx = attributes.begin()
 		 ; idx != attributes.end()
 		 ; idx ++) {
 	    out << "        " << (*idx).first;
@@ -678,7 +678,7 @@ void PProcess::dump(ostream&out, unsigned ind) const
 
       out << " /* " << get_line() << " */" << endl;
 
-      for (map<string,PExpr*>::const_iterator idx = attributes.begin()
+      for (map<perm_string,PExpr*>::const_iterator idx = attributes.begin()
 		 ; idx != attributes.end() ; idx++ ) {
 
 	    out << setw(ind+2) << "" << "(* " << (*idx).first;
@@ -695,7 +695,7 @@ void Module::dump(ostream&out) const
 {
       if (attributes.begin() != attributes.end()) {
 	    out << "(* ";
-	    for (map<string,PExpr*>::const_iterator idx = attributes.begin()
+	    for (map<perm_string,PExpr*>::const_iterator idx = attributes.begin()
 		 ; idx != attributes.end() ; idx++ ) {
 		    if (idx != attributes.begin()) {
 			out << " , ";
@@ -881,6 +881,9 @@ void PUdp::dump(ostream&out) const
 
 /*
  * $Log: pform_dump.cc,v $
+ * Revision 1.85  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.84  2004/02/20 06:22:58  steve
  *  parameter keys are per_strings.
  *
diff --git a/syn-rules.y b/syn-rules.y
index ff570c514..9b8168780 100644
--- a/syn-rules.y
+++ b/syn-rules.y
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: syn-rules.y,v 1.28 2003/12/20 00:59:31 steve Exp $"
+#ident "$Id: syn-rules.y,v 1.29 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -127,9 +127,9 @@ static void hookup_DFF_CE(NetFF*ff, NetESignal*d, NetEvProbe*pclk,
       connect(ff->pin_Clock(), pclk->pin(0));
       if (ce) connect(ff->pin_Enable(), ce->pin(0));
 
-      ff->attribute("LPM_FFType", verinum("DFF"));
+      ff->attribute(perm_string::literal("LPM_FFType"), verinum("DFF"));
       if (pclk->edge() == NetEvProbe::NEGEDGE)
-	    ff->attribute("Clock:LPM_Polarity", verinum("INVERT"));
+	    ff->attribute(perm_string::literal("Clock:LPM_Polarity"), verinum("INVERT"));
 
 }
 
@@ -406,7 +406,7 @@ struct syn_rules_f  : public functor_t {
       {
 	      /* If the scope that contains this process as a cell
 		 attribute attached to it, then skip synthesis. */
-	    if (top->scope()->attribute("ivl_synthesis_cell").len() > 0)
+	    if (top->scope()->attribute(perm_string::literal("ivl_synthesis_cell")).len() > 0)
 		  return;
 
 	    syn_start_process(top);
diff --git a/synth2.cc b/synth2.cc
index 2bf2fdbce..167b7d095 100644
--- a/synth2.cc
+++ b/synth2.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: synth2.cc,v 1.35 2004/02/18 17:11:58 steve Exp $"
+#ident "$Id: synth2.cc,v 1.36 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -839,7 +839,7 @@ bool NetEvWait::synth_sync(Design*des, NetScope*scope, NetFF*ff,
 
       connect(ff->pin_Clock(), pclk->pin(0));
       if (pclk->edge() == NetEvProbe::NEGEDGE)
-	    ff->attribute("Clock:LPM_Polarity", verinum("INVERT"));
+	    ff->attribute(perm_string::literal("Clock:LPM_Polarity"), verinum("INVERT"));
 
 	/* Synthesize the input to the DFF. */
       bool flag = statement_->synth_sync(des, scope, ff,
@@ -858,7 +858,7 @@ bool NetProcTop::synth_sync(Design*des)
       NetFF*ff = new NetFF(scope(), scope()->local_symbol(),
 			   nex_set.count());
       des->add_node(ff);
-      ff->attribute("LPM_FFType", verinum("DFF"));
+      ff->attribute(perm_string::literal("LPM_FFType"), verinum("DFF"));
 
 	/* The D inputs to the DFF device will receive the output from
 	   the statements of the process. */
@@ -906,12 +906,12 @@ class synth2_f  : public functor_t {
  */
 void synth2_f::process(class Design*des, class NetProcTop*top)
 {
-      if (top->attribute("ivl_synthesis_off").as_ulong() != 0)
+      if (top->attribute(perm_string::literal("ivl_synthesis_off")).as_ulong() != 0)
 	    return;
 
 	/* If the scope that contains this process as a cell attribute
 	   attached to it, then skip synthesis. */
-      if (top->scope()->attribute("ivl_synthesis_cell").len() > 0)
+      if (top->scope()->attribute(perm_string::literal("ivl_synthesis_cell")).len() > 0)
 	    return;
 
       if (top->is_synchronous()) do {
@@ -928,7 +928,7 @@ void synth2_f::process(class Design*des, class NetProcTop*top)
 
       if (! top->is_asynchronous()) {
 	    bool synth_error_flag = false;
-	    if (top->attribute("ivl_combinational").as_ulong() != 0) {
+	    if (top->attribute(perm_string::literal("ivl_combinational")).as_ulong() != 0) {
 		  cerr << top->get_line() << ": error: "
 		       << "Process is marked combinational,"
 		       << " but isn't really." << endl;
@@ -936,7 +936,7 @@ void synth2_f::process(class Design*des, class NetProcTop*top)
 		  synth_error_flag = true;
 	    }
 
-	    if (top->attribute("ivl_synthesis_on").as_ulong() != 0) {
+	    if (top->attribute(perm_string::literal("ivl_synthesis_on")).as_ulong() != 0) {
 		  cerr << top->get_line() << ": error: "
 		       << "Process is marked for synthesis,"
 		       << " but I can't do it." << endl;
@@ -970,6 +970,9 @@ void synth2(Design*des)
 
 /*
  * $Log: synth2.cc,v $
+ * Revision 1.36  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.35  2004/02/18 17:11:58  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/t-dll.cc b/t-dll.cc
index 691cd7b13..b6bc9d6be 100644
--- a/t-dll.cc
+++ b/t-dll.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-dll.cc,v 1.128 2004/02/20 06:22:58 steve Exp $"
+#ident "$Id: t-dll.cc,v 1.129 2004/02/20 18:53:35 steve Exp $"
 #endif
 
 # include "config.h"
@@ -162,7 +162,7 @@ ivl_attribute_s* dll_target::fill_in_attributes(const Attrib*net)
 
       for (unsigned idx = 0 ;  idx < nattr ;  idx += 1) {
 	    verinum tmp = net->attr_value(idx);
-	    attr[idx].key = strings_.add(net->attr_key(idx));
+	    attr[idx].key = net->attr_key(idx);
 	    if (tmp.is_string()) {
 		  attr[idx].type = IVL_ATT_STR;
 		  attr[idx].val.str = strings_.add(tmp.as_string().c_str());
@@ -1100,7 +1100,7 @@ void dll_target::memory(const NetMemory*net)
 void dll_target::lpm_add_sub(const NetAddSub*net)
 {
       ivl_lpm_t obj = new struct ivl_lpm_s;
-      if (net->attribute("LPM_Direction") == verinum("SUB"))
+      if (net->attribute(perm_string::literal("LPM_Direction")) == verinum("SUB"))
 	    obj->type = IVL_LPM_SUB;
       else
 	    obj->type = IVL_LPM_ADD;
@@ -2176,6 +2176,9 @@ extern const struct target tgt_dll = { "dll", &dll_target_obj };
 
 /*
  * $Log: t-dll.cc,v $
+ * Revision 1.129  2004/02/20 18:53:35  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.128  2004/02/20 06:22:58  steve
  *  parameter keys are per_strings.
  *
diff --git a/t-xnf.cc b/t-xnf.cc
index 38fa923d2..e6bf20bc8 100644
--- a/t-xnf.cc
+++ b/t-xnf.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-xnf.cc,v 1.51 2004/02/18 17:11:58 steve Exp $"
+#ident "$Id: t-xnf.cc,v 1.52 2004/02/20 18:53:36 steve Exp $"
 #endif
 
 # include "config.h"
@@ -347,7 +347,7 @@ void target_xnf::signal(const NetNet*net)
 	/* Now look to see if a PAD attribute is attached, and if so
 	   write out PAD information to the XNF and the ncf files. */
 
-      string pad = net->attribute("PAD").as_string();
+      string pad = net->attribute(perm_string::literal("PAD")).as_string();
       if (pad == "")
 	    return;
 
@@ -682,19 +682,19 @@ void target_xnf::lpm_compare_le_(ostream&os, const NetCompare*dev)
 
 void target_xnf::lpm_ff(const NetFF*net)
 {
-      string type = net->attribute("LPM_FFType").as_string();
+      string type = net->attribute(perm_string::literal("LPM_FFType")).as_string();
       if (type == "") type = "DFF";
 
 	// XXXX For now, only support DFF
       assert(type == "DFF");
 
-      string lcaname = net->attribute("XNF-LCA").as_string();
+      string lcaname = net->attribute(perm_string::literal("XNF-LCA")).as_string();
       if (lcaname != "") {
 	    draw_sym_with_lcaname(out_, lcaname, net);
 	    return;
       }
 
-      assert(net->attribute("XNF-LCA") == verinum(""));
+      assert(net->attribute(perm_string::literal("XNF-LCA")) == verinum(""));
 
 	/* Create a DFF object for each bit of width. The symbol name
 	   has the index number appended so that read XNF may be able
@@ -724,7 +724,7 @@ void target_xnf::lpm_ff(const NetFF*net)
 	    draw_pin(out_, "Q", net->pin_Q(idx));
 	    draw_pin(out_, "D", net->pin_Data(idx));
 
-	    if (net->attribute("Clock:LPM_Polarity") == verinum("INVERT"))
+	    if (net->attribute(perm_string::literal("Clock:LPM_Polarity")) == verinum("INVERT"))
 		  draw_pin(out_, "~C", net->pin_Clock());
 	    else
 		  draw_pin(out_, "C", net->pin_Clock());
@@ -822,7 +822,7 @@ void target_xnf::logic(const NetLogic*net)
 {
 	// The XNF-LCA attribute overrides anything I might guess
 	// about this object.
-      string lca = net->attribute("XNF-LCA").as_string();
+      string lca = net->attribute(perm_string::literal("XNF-LCA")).as_string();
       if (lca != "") {
 	    draw_sym_with_lcaname(out_, lca, net);
 	    return;
@@ -920,7 +920,7 @@ bool target_xnf::bufz(const NetBUFZ*net)
 
 void target_xnf::udp(const NetUDP*net)
 {
-      string lca = net->attribute("XNF-LCA").as_string();
+      string lca = net->attribute(perm_string::literal("XNF-LCA")).as_string();
 
 	// I only know how to draw a UDP if it has the XNF-LCA
 	// attribute attached to it.
@@ -938,6 +938,9 @@ extern const struct target tgt_xnf = { "xnf", &target_xnf_obj };
 
 /*
  * $Log: t-xnf.cc,v $
+ * Revision 1.52  2004/02/20 18:53:36  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.51  2004/02/18 17:11:58  steve
  *  Use perm_strings for named langiage items.
  *
diff --git a/util.h b/util.h
index 777831923..c51ae786e 100644
--- a/util.h
+++ b/util.h
@@ -1,7 +1,7 @@
 #ifndef __util_H
 #define __util_H
 /*
- * Copyright (c) 2000 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2004 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
@@ -19,11 +19,11 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: util.h,v 1.6 2002/08/12 01:35:01 steve Exp $"
+#ident "$Id: util.h,v 1.7 2004/02/20 18:53:36 steve Exp $"
 #endif
 
 # include  <map>
-# include  <string>
+# include  "StringHeap.h"
 # include  "verinum.h"
 
 class PExpr;
@@ -40,17 +40,20 @@ extern bool load_module(const char*type);
 
 
 struct attrib_list_t {
-      string key;
+      perm_string key;
       verinum val;
 };
 
-extern attrib_list_t* evaluate_attributes(const map<string,PExpr*>&att,
+extern attrib_list_t* evaluate_attributes(const map<perm_string,PExpr*>&att,
 					  unsigned&natt,
 					  const Design*des,
 					  const NetScope*scope);
 
 /*
  * $Log: util.h,v $
+ * Revision 1.7  2004/02/20 18:53:36  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.6  2002/08/12 01:35:01  steve
  *  conditional ident string using autoconfig.
  *
diff --git a/xnfio.cc b/xnfio.cc
index afe4492f8..85cb0b642 100644
--- a/xnfio.cc
+++ b/xnfio.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: xnfio.cc,v 1.28 2004/02/18 17:11:58 steve Exp $"
+#ident "$Id: xnfio.cc,v 1.29 2004/02/20 18:53:36 steve Exp $"
 #endif
 
 # include "config.h"
@@ -40,7 +40,7 @@ class xnfio_f  : public functor_t {
 
 static bool is_a_pad(const NetNet*net)
 {
-      if (net->attribute("PAD") == verinum())
+      if (net->attribute(perm_string::literal("PAD")) == verinum())
 	    return false;
 
       return true;
@@ -89,7 +89,8 @@ static NetLogic* make_obuf(Design*des, NetNet*net)
 		&& (count_inputs(tmp->pin(0)) == 0)
 		&& (count_outputs(tmp->pin(0)) == 1)
 		&& (idx->get_pin() == 0)  ) {
-		  tmp->attribute("XNF-LCA", verinum("OBUF:O,I"));
+		  tmp->attribute(perm_string::literal("XNF-LCA"),
+				 verinum("OBUF:O,I"));
 		  return tmp;
 	    }
 
@@ -102,7 +103,8 @@ static NetLogic* make_obuf(Design*des, NetNet*net)
 		&& (count_inputs(tmp->pin(0)) == 0)
 		&& (count_outputs(tmp->pin(0)) == 1)
 		&& (idx->get_pin() == 0)  ) {
-		  tmp->attribute("XNF-LCA", verinum("OBUF:O,~I"));
+		  tmp->attribute(perm_string::literal("XNF-LCA"),
+				 verinum("OBUF:O,~I"));
 		  return tmp;
 	    }
 
@@ -114,7 +116,8 @@ static NetLogic* make_obuf(Design*des, NetNet*net)
 		&& (count_inputs(tmp->pin(0)) == 0)
 		&& (count_outputs(tmp->pin(0)) == 1)
 		&& (idx->get_pin() == 0)  ) {
-		  tmp->attribute("XNF-LCA", verinum("OBUFT:O,I,~T"));
+		  tmp->attribute(perm_string::literal("XNF-LCA"),
+				 verinum("OBUFT:O,I,~T"));
 		  return tmp;
 	    }
 
@@ -122,7 +125,8 @@ static NetLogic* make_obuf(Design*des, NetNet*net)
 		&& (count_inputs(tmp->pin(0)) == 0)
 		&& (count_outputs(tmp->pin(0)) == 1)
 		&& (idx->get_pin() == 0)  ) {
-		  tmp->attribute("XNF-LCA", verinum("OBUFT:O,I,T"));
+		  tmp->attribute(perm_string::literal("XNF-LCA"),
+				 verinum("OBUFT:O,I,T"));
 		  return tmp;
 	    }
       }
@@ -133,7 +137,7 @@ static NetLogic* make_obuf(Design*des, NetNet*net)
 				  2, NetLogic::BUF);
       des->add_node(buf);
 
-      buf->attribute("XNF-LCA", verinum("OBUF:O,I"));
+      buf->attribute(perm_string::literal("XNF-LCA"), verinum("OBUF:O,I"));
 
 	// Put the buffer between this signal and the rest of the
 	// netlist.
@@ -175,7 +179,7 @@ static void absorb_OFF(Design*des, NetLogic*buf)
 	    return;
       if (ff->width() != 1)
 	    return;
-      if (ff->attribute("LPM_FFType") != verinum("DFF"))
+      if (ff->attribute(perm_string::literal("LPM_FFType")) != verinum("DFF"))
 	    return;
 
 	/* Connect the flip-flop output to the buffer output and
@@ -189,7 +193,7 @@ static void absorb_OFF(Design*des, NetLogic*buf)
       for (unsigned idx = 0 ;  idx < ff->pin_count() ;  idx += 1)
 	    names[idx] = "";
 
-      if (ff->attribute("Clock:LPM_Polarity") == verinum("INVERT"))
+      if (ff->attribute(perm_string::literal("Clock:LPM_Polarity")) == verinum("INVERT"))
 	    names[ff->pin_Clock().get_pin()] = "~C";
       else
 	    names[ff->pin_Clock().get_pin()] = "C";
@@ -202,7 +206,7 @@ static void absorb_OFF(Design*des, NetLogic*buf)
 	    lname = lname + "," + names[idx];
       delete[]names;
 
-      ff->attribute("XNF-LCA", lname);
+      ff->attribute(perm_string::literal("XNF-LCA"), lname);
 }
 
 static void make_ibuf(Design*des, NetNet*net)
@@ -224,7 +228,7 @@ static void make_ibuf(Design*des, NetNet*net)
 	    if ((tmp = dynamic_cast<NetLogic*>(idx->get_obj())) == 0)
 		  continue;
 
-	    if (tmp->attribute("XNF-LCA") != verinum())
+	    if (tmp->attribute(perm_string::literal("XNF-LCA")) != verinum())
 		  continue;
 
 	      // Found a BUF, it is only usable if the only input is
@@ -232,7 +236,7 @@ static void make_ibuf(Design*des, NetNet*net)
 	    if ((tmp->type() == NetLogic::BUF) &&
 		(count_inputs(tmp->pin(1)) == 1) &&
 		(count_outputs(tmp->pin(1)) == 0)) {
-		  tmp->attribute("XNF-LCA", verinum("IBUF:O,I"));
+		  tmp->attribute(perm_string::literal("XNF-LCA"), verinum("IBUF:O,I"));
 		  return;
 	    }
 
@@ -243,7 +247,7 @@ static void make_ibuf(Design*des, NetNet*net)
 				  2, NetLogic::BUF);
       des->add_node(buf);
 
-      buf->attribute("XNF-LCA", verinum("IBUF:O,I"));
+      buf->attribute(perm_string::literal("XNF-LCA"), verinum("IBUF:O,I"));
 
 	// Put the buffer between this signal and the rest of the
 	// netlist.
@@ -268,7 +272,7 @@ void xnfio_f::signal(Design*des, NetNet*net)
 	    return;
 
       assert(net->pin_count() == 1);
-      string pattr = net->attribute("PAD").as_string();
+      string pattr = net->attribute(perm_string::literal("PAD")).as_string();
 
       switch (pattr[0]) {
 	  case 'i':
@@ -361,6 +365,9 @@ void xnfio(Design*des)
 
 /*
  * $Log: xnfio.cc,v $
+ * Revision 1.29  2004/02/20 18:53:36  steve
+ *  Addtrbute keys are perm_strings.
+ *
  * Revision 1.28  2004/02/18 17:11:58  steve
  *  Use perm_strings for named langiage items.
  *