diff --git a/PExpr.cc b/PExpr.cc
index 96428204f..751d2be5f 100644
--- a/PExpr.cc
+++ b/PExpr.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2007 Stephen Williams <steve@icarus.com>
+ * Copyright (c) 1998-2008 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
@@ -20,6 +20,7 @@
 # include "config.h"
 
 # include  <iostream>
+# include  <cstring>
 
 # include  "PExpr.h"
 # include  "Module.h"
@@ -117,6 +118,26 @@ PECallFunction::~PECallFunction()
 {
 }
 
+bool PECallFunction::is_constant(Module*mod) const
+{
+	/* Only $clog2 can be a constant system function. */
+      if (peek_tail_name(path_)[0] == '$') {
+	    if (strcmp(peek_tail_name(path_).str(), "$clog2") == 0) {
+		  if (parms_.count() != 1 || parms_[0] == 0) {
+			cerr << get_fileline() << ": error: $clog2 takes a "
+			                          "single argument." << endl;
+			return false;
+		  }
+		    /* If the argument is constant $clog2 is constant. */
+		  return parms_[0]->is_constant(mod);
+	    }
+	    return false;  /* Most system functions are not constant. */
+      }
+
+	/* Checking for constant user functions goes here. */
+      return false;
+}
+
 PEConcat::PEConcat(const svector<PExpr*>&p, PExpr*r)
 : parms_(p), repeat_(r)
 {
@@ -299,4 +320,3 @@ bool PEUnary::is_constant(Module*m) const
 {
       return expr_->is_constant(m);
 }
-
diff --git a/PExpr.h b/PExpr.h
index a06a59015..fdb0d725f 100644
--- a/PExpr.h
+++ b/PExpr.h
@@ -710,6 +710,8 @@ class PECallFunction : public PExpr {
       explicit PECallFunction(perm_string n);
       ~PECallFunction();
 
+      virtual bool is_constant(Module*) const;
+
       virtual void dump(ostream &) const;
 
       virtual NetNet* elaborate_net(Design*des, NetScope*scope,
@@ -721,6 +723,7 @@ class PECallFunction : public PExpr {
 				    Link::strength_t drive1) const;
       virtual NetExpr*elaborate_expr(Design*des, NetScope*scope,
 				     int expr_wid, bool sys_task_arg) const;
+      virtual NetExpr*elaborate_pexpr(Design*des, NetScope*sc) const;
 
       virtual unsigned test_width(Design*des, NetScope*scope,
 				  unsigned min, unsigned lval,
diff --git a/PFunction.cc b/PFunction.cc
index fb26c434b..1a3146a8a 100644
--- a/PFunction.cc
+++ b/PFunction.cc
@@ -21,9 +21,10 @@
 
 #include "PTask.h"
 
-PFunction::PFunction(perm_string name, PScope*parent)
+PFunction::PFunction(perm_string name, PScope*parent, bool is_auto)
 : PScope(name, parent), ports_(0), statement_(0)
 {
+      is_auto_ = is_auto;
       return_type_.type = PTF_NONE;
 }
 
diff --git a/PTask.cc b/PTask.cc
index b829e03f2..3719c4b3c 100644
--- a/PTask.cc
+++ b/PTask.cc
@@ -21,9 +21,10 @@
 
 # include  "PTask.h"
 
-PTask::PTask(perm_string name, PScope*parent)
+PTask::PTask(perm_string name, PScope*parent, bool is_auto)
 : PScope(name, parent), ports_(0), statement_(0)
 {
+      is_auto_ = is_auto;
 }
 
 PTask::~PTask()
@@ -41,31 +42,3 @@ void PTask::set_statement(Statement*s)
       assert(statement_ == 0);
       statement_ = s;
 }
-
-
-/*
- * $Log: PTask.cc,v $
- * Revision 1.7  2002/08/12 01:34:58  steve
- *  conditional ident string using autoconfig.
- *
- * Revision 1.6  2001/07/25 03:10:48  steve
- *  Create a config.h.in file to hold all the config
- *  junk, and support gcc 3.0. (Stephan Boettcher)
- *
- * Revision 1.5  2001/04/19 03:04:47  steve
- *  Spurious assert of empty statemnt.
- *
- * Revision 1.4  2001/01/13 22:20:08  steve
- *  Parse parameters within nested scopes.
- *
- * Revision 1.3  2000/02/23 02:56:53  steve
- *  Macintosh compilers do not support ident.
- *
- * Revision 1.2  1999/07/24 02:11:19  steve
- *  Elaborate task input ports.
- *
- * Revision 1.1  1999/07/03 02:12:51  steve
- *  Elaborate user defined tasks.
- *
- */
-
diff --git a/PTask.h b/PTask.h
index 4d9c24e9c..de05ac053 100644
--- a/PTask.h
+++ b/PTask.h
@@ -51,7 +51,7 @@ struct PTaskFuncArg {
 class PTask  : public PScope, public LineInfo {
 
     public:
-      explicit PTask(perm_string name, PScope*parent);
+      explicit PTask(perm_string name, PScope*parent, bool is_auto);
       ~PTask();
 
       void set_ports(svector<PWire *>*p);
@@ -69,11 +69,14 @@ class PTask  : public PScope, public LineInfo {
 	// Elaborate the statement to finish off the task definition.
       void elaborate(Design*des, NetScope*scope) const;
 
+      bool is_auto() const { return is_auto_; };
+
       void dump(ostream&, unsigned) const;
 
     private:
       svector<PWire*>*ports_;
       Statement*statement_;
+      bool is_auto_;
 
     private: // Not implemented
       PTask(const PTask&);
@@ -90,7 +93,7 @@ class PTask  : public PScope, public LineInfo {
 class PFunction : public PScope, public LineInfo {
 
     public:
-      explicit PFunction(perm_string name, PScope*parent);
+      explicit PFunction(perm_string name, PScope*parent, bool is_auto);
       ~PFunction();
 
       void set_ports(svector<PWire *>*p);
@@ -105,12 +108,15 @@ class PFunction : public PScope, public LineInfo {
 	/* Elaborate the behavioral statement. */
       void elaborate(Design *des, NetScope*) const;
 
+      bool is_auto() const { return is_auto_; };
+
       void dump(ostream&, unsigned) const;
 
     private:
       PTaskFuncArg return_type_;
       svector<PWire *> *ports_;
       Statement *statement_;
+      bool is_auto_;
 };
 
 #endif
diff --git a/design_dump.cc b/design_dump.cc
index ca8e71d8e..1af627745 100644
--- a/design_dump.cc
+++ b/design_dump.cc
@@ -998,6 +998,7 @@ void NetScope::dump(ostream&o) const
 	    o << " generate block";
 	    break;
       }
+      if (is_auto()) o << " (automatic)";
       o << endl;
 
       for (unsigned idx = 0 ;  idx < attr_cnt() ;  idx += 1)
diff --git a/elab_expr.cc b/elab_expr.cc
index 2258ef78c..c496b04de 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -653,7 +653,7 @@ NetExpr* PECallFunction::elaborate_sfunc_(Design*des, NetScope*scope, int expr_w
 		  delete tmp;
 	    }
 
-	    verinum val (sub_expr_width, 8*sizeof(unsigned));
+	    verinum val ( (uint64_t)sub_expr_width, 8*sizeof(unsigned));
 	    NetEConst*sub = new NetEConst(val);
 	    sub->set_line(*this);
 
@@ -1653,7 +1653,7 @@ NetExpr* PEIdent::elaborate_expr_net_word_(Design*des, NetScope*scope,
 	      // Recalculate the constant address with the adjusted base.
 	    unsigned use_addr = net->array_index_to_address(addr);
 	    if (addr < 0 || use_addr != (unsigned long)addr) {
-		  verinum val (use_addr, 8*sizeof(use_addr));
+		  verinum val ( (uint64_t)use_addr, 8*sizeof(use_addr));
 		  NetEConst*tmp = new NetEConst(val);
 		  tmp->set_line(*this);
 		  delete word_index;
diff --git a/elab_pexpr.cc b/elab_pexpr.cc
index a3d398a47..e4cdbe087 100644
--- a/elab_pexpr.cc
+++ b/elab_pexpr.cc
@@ -25,6 +25,7 @@
 # include  "netmisc.h"
 
 # include  <cstdlib>
+# include  <cstring>
 # include  <iostream>
 # include  "ivl_assert.h"
 
@@ -267,3 +268,40 @@ NetExpr*PEUnary::elaborate_pexpr (Design*des, NetScope*scope) const
 
       return tmp;
 }
+
+/* Reuse the routine from eval_tree.cc. */
+NetExpr* evaluate_clog2(NetExpr*arg);
+
+NetExpr* PECallFunction::elaborate_pexpr(Design*des, NetScope*scope) const
+{
+	/* For now only $clog2 can be a constant system function. */
+      if (peek_tail_name(path_)[0] == '$') {
+	    if (strcmp(peek_tail_name(path_).str(), "$clog2") == 0) {
+		  if (parms_.count() != 1 || parms_[0] == 0) {
+			cerr << get_fileline() << ": error: $clog2 takes a "
+			                          "single argument." << endl;
+			des->errors += 1;
+			return 0;
+		  }
+		  NetExpr*arg = parms_[0]->elaborate_pexpr(des, scope);
+		  eval_expr(arg);
+		  NetExpr*rtn = evaluate_clog2(arg);
+		  delete arg;
+		  if (rtn != 0) {
+			rtn->set_line(*this);
+			return rtn;
+		  }
+	    }
+
+	    cerr << get_fileline() << ": error: this is not a constant "
+	            "system function (" << *this << ")." << endl;
+	    des->errors += 1;
+	    return 0;
+      }
+
+	/* Constant user function code goes here. */
+      cerr << get_fileline() << ": sorry: constant user functions are not "
+                                "currently supported." << endl;
+      des->errors += 1;
+      return 0;
+}
diff --git a/elab_scope.cc b/elab_scope.cc
index b77292dea..5df05b7bc 100644
--- a/elab_scope.cc
+++ b/elab_scope.cc
@@ -150,6 +150,7 @@ static void elaborate_scope_tasks(Design*des, NetScope*scope,
 	    }
 	    NetScope*task_scope = new NetScope(scope, use_name,
 					       NetScope::TASK);
+	    task_scope->is_auto((*cur).second->is_auto());
 	    task_scope->set_line((*cur).second);
 
 	    if (debug_scopes)
@@ -179,6 +180,7 @@ static void elaborate_scope_funcs(Design*des, NetScope*scope,
 	    }
 	    NetScope*func_scope = new NetScope(scope, use_name,
 					       NetScope::FUNC);
+	    func_scope->is_auto((*cur).second->is_auto());
 	    func_scope->set_line((*cur).second);
 
 	    if (debug_scopes)
diff --git a/elaborate.cc b/elaborate.cc
index 23ce93fff..deaa14d1a 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -2532,8 +2532,8 @@ NetProc* PEventStatement::elaborate_st(Design*des, NetScope*scope,
 	    }
 	    NexusSet*nset = enet->nex_input(rem_out);
 	    if (nset == 0) {
-		  cerr << get_fileline() << ": internal error: No NexusSet"
-		       << " from statement." << endl;
+		  cerr << get_fileline() << ": error: Unable to elaborate:"
+		       << endl;
 		  enet->dump(cerr, 6);
 		  des->errors += 1;
 		  return enet;
diff --git a/eval_tree.cc b/eval_tree.cc
index 4a831ce2f..422e14f48 100644
--- a/eval_tree.cc
+++ b/eval_tree.cc
@@ -22,6 +22,8 @@
 
 # include  <iostream>
 # include  <cstdlib>
+# include  <cstring>
+# include  <math.h>
 
 # include  "netlist.h"
 # include  "ivl_assert.h"
@@ -1620,3 +1622,67 @@ NetEConst* NetEUReduce::eval_tree(int prune_to_width)
 
       return new NetEConst(verinum(res, 1));
 }
+
+NetExpr* evaluate_clog2(NetExpr*arg)
+{
+      NetEConst*tmpi = dynamic_cast<NetEConst *>(arg);
+      NetECReal*tmpr = dynamic_cast<NetECReal *>(arg);
+      bool is_neg = false;
+      if (tmpi || tmpr) {
+	    verinum arg;
+	    if (tmpi) {
+		  arg = tmpi->value();
+	    } else {
+		  arg = verinum(tmpr->value().as_double(), true);
+	    }
+
+	      /* If we have an x in the verinum we return 32'bx. */
+	    if (!arg.is_defined()) {
+		  verinum tmp (verinum::Vx, 32);
+		  tmp.has_sign(true);
+		  NetEConst*rtn = new NetEConst(tmp);
+		  return rtn;
+	    }
+
+	    uint64_t res = 0;
+	    if (arg.is_negative()) is_neg = true;
+	    arg.has_sign(false);  // $unsigned()
+	    if (!arg.is_zero()) {
+		  arg = arg - verinum((uint64_t)1, 1);
+		  while (!arg.is_zero()) {
+			res += 1;
+			arg = arg >> 1;
+		  }
+	    }
+	    if (is_neg && res < 32) res = 32;
+	    verinum tmp (res, 32);
+	    tmp.has_sign(true);
+	    NetEConst*rtn = new NetEConst(tmp);
+	    return rtn;
+      }
+
+      return 0;
+}
+
+NetExpr* NetESFunc::eval_tree(int prune_to_width)
+{
+	/* For now only $clog2 can be a constant system function. */
+      if (strcmp(name(), "$clog2") == 0) {
+	    if (nparms() != 1 || parm(0) == 0) {
+		  cerr << get_fileline() << ": error: $clog2 takes a single "
+		                            "argument." << endl;
+		  return 0;
+	    }
+	    NetExpr*rtn = evaluate_clog2(parm(0));
+	    if (rtn != 0) {
+		  rtn->set_line(*this);
+		  if (debug_eval_tree) {
+			cerr << get_fileline() << ": debug: Evaluate "
+			        "constant $clog2()." << endl;
+		  }
+		  return rtn;
+	    }
+      }
+
+      return 0;
+}
diff --git a/ivl.def b/ivl.def
index dfcf064cf..22260e7e9 100644
--- a/ivl.def
+++ b/ivl.def
@@ -143,6 +143,7 @@ ivl_scope_def_lineno
 ivl_scope_event
 ivl_scope_events
 ivl_scope_file
+ivl_scope_is_auto
 ivl_scope_lineno
 ivl_scope_logs
 ivl_scope_log
diff --git a/ivl_target.h b/ivl_target.h
index 7535bd0d4..f04d90f8a 100644
--- a/ivl_target.h
+++ b/ivl_target.h
@@ -1447,6 +1447,9 @@ extern unsigned ivl_parameter_lineno(ivl_parameter_t net);
  * ivl_scope_lineno
  *    Returns the instantiation file and line for this scope.
  *
+ * ivl_scope_is_auto
+ *    Is the task or function declared to be automatic?
+ *
  * ivl_scope_var
  * ivl_scope_vars
  *    REMOVED
@@ -1523,6 +1526,7 @@ extern unsigned ivl_scope_def_lineno(ivl_scope_t net);
 extern unsigned     ivl_scope_events(ivl_scope_t net);
 extern ivl_event_t  ivl_scope_event(ivl_scope_t net, unsigned idx);
 extern const char* ivl_scope_file(ivl_scope_t net);
+extern unsigned ivl_scope_is_auto(ivl_scope_t net);
 extern unsigned ivl_scope_lineno(ivl_scope_t net);
 extern unsigned     ivl_scope_logs(ivl_scope_t net);
 extern ivl_net_logic_t ivl_scope_log(ivl_scope_t net, unsigned idx);
diff --git a/lexor_keyword.gperf b/lexor_keyword.gperf
index 980b33c89..9cb72b281 100644
--- a/lexor_keyword.gperf
+++ b/lexor_keyword.gperf
@@ -25,6 +25,7 @@ assign,		GN_KEYWORDS_1364_1995,	K_assign
 atan,		GN_KEYWORDS_VAMS_2_3,	K_atan
 atan2,		GN_KEYWORDS_VAMS_2_3,	K_atan2
 atanh,		GN_KEYWORDS_VAMS_2_3,	K_atanh
+automatic,	GN_KEYWORDS_1364_2001,	K_automatic
 begin,		GN_KEYWORDS_1364_1995,	K_begin
 bool,		GN_KEYWORDS_ICARUS,	K_bool
 buf,		GN_KEYWORDS_1364_1995,	K_buf
diff --git a/net_nex_input.cc b/net_nex_input.cc
index 2a68c2a8b..0f97c2a44 100644
--- a/net_nex_input.cc
+++ b/net_nex_input.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2007 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2002-2008 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
@@ -53,8 +53,13 @@ NexusSet* NetEBinary::nex_input(bool rem_out)
 
 NexusSet* NetEConcat::nex_input(bool rem_out)
 {
+      if (parms_[0] == NULL) return NULL;
       NexusSet*result = parms_[0]->nex_input(rem_out);
       for (unsigned idx = 1 ;  idx < parms_.count() ;  idx += 1) {
+	    if (parms_[idx] == NULL) {
+		  delete result;
+		  return NULL;
+	    }
 	    NexusSet*tmp = parms_[idx]->nex_input(rem_out);
 	    result->add(*tmp);
 	    delete tmp;
@@ -98,6 +103,10 @@ NexusSet* NetESelect::nex_input(bool rem_out)
 {
       NexusSet*result = base_? base_->nex_input(rem_out) : new NexusSet();
       NexusSet*tmp = expr_->nex_input(rem_out);
+      if (tmp == NULL) {
+	    delete result;
+	    return NULL;
+      }
       result->add(*tmp);
       delete tmp;
       return result;
@@ -381,4 +390,3 @@ NexusSet* NetWhile::nex_input(bool rem_out)
       delete tmp;
       return result;
 }
-
diff --git a/net_scope.cc b/net_scope.cc
index 2b8baf0cb..d39152cdc 100644
--- a/net_scope.cc
+++ b/net_scope.cc
@@ -41,6 +41,7 @@ NetScope::NetScope(NetScope*up, const hname_t&n, NetScope::TYPE t)
       signals_ = 0;
       events_ = 0;
       lcounter_ = 0;
+      is_auto_ = false;
 
       if (up) {
 	    default_nettype_ = up->default_nettype();
@@ -261,6 +262,7 @@ NetFuncDef* NetScope::func_def()
       assert( type_ == FUNC );
       return func_;
 }
+
 bool NetScope::in_func()
 {
       return (type_ == FUNC) ? true : false;
diff --git a/netlist.h b/netlist.h
index aaef219d2..633092c58 100644
--- a/netlist.h
+++ b/netlist.h
@@ -697,6 +697,9 @@ class NetScope : public Attrib {
       unsigned get_def_lineno() const { return def_lineno_; };
 
       bool in_func();
+	/* Is the task or function automatic. */
+      void is_auto(bool is_auto) { is_auto_ = is_auto; };
+      bool is_auto() const { return is_auto_; }; 
 
       const NetTaskDef* task_def() const;
       const NetFuncDef* func_def() const;
@@ -840,6 +843,7 @@ class NetScope : public Attrib {
       NetScope*sub_;
 
       unsigned lcounter_;
+      bool is_auto_;
 };
 
 /*
@@ -3455,6 +3459,8 @@ class NetESFunc  : public NetExpr {
       NetExpr* parm(unsigned idx);
       const NetExpr* parm(unsigned idx) const;
 
+      virtual NetExpr* eval_tree(int prune_to_width = -1);
+
       virtual ivl_variable_type_t expr_type() const;
       virtual NexusSet* nex_input(bool rem_out = true);
       virtual bool set_width(unsigned, bool last_chance);
diff --git a/parse.y b/parse.y
index 7382eae6b..4b2dae490 100644
--- a/parse.y
+++ b/parse.y
@@ -205,7 +205,7 @@ static PECallFunction*make_call_function(perm_string tn, PExpr*arg1, PExpr*arg2)
 %token K_PSTAR K_STARP
 %token K_LOR K_LAND K_NAND K_NOR K_NXOR K_TRIGGER
 %token K_abs K_abstol K_access K_acos K_acosh K_asin K_analog K_asinh
-%token K_atan K_atanh K_atan2
+%token K_atan K_atanh K_atan2 K_automatic
 %token K_always K_and K_assign K_begin K_bool K_buf K_bufif0 K_bufif1 K_case
 %token K_casex K_casez K_ceil K_cmos K_continuous K_cos K_cosh
 %token K_ddt_nature K_deassign K_default K_defparam K_disable K_discrete
@@ -239,7 +239,7 @@ static PECallFunction*make_call_function(perm_string tn, PExpr*arg1, PExpr*arg2)
 
 %type <flag>    from_exclude
 %type <number>  number
-%type <flag>    signed_opt udp_reg_opt edge_operator
+%type <flag>    signed_opt udp_reg_opt edge_operator automatic_opt
 %type <drive>   drive_strength drive_strength_opt dr_strength0 dr_strength1
 %type <letter>  udp_input_sym udp_output_sym
 %type <text>    udp_input_list udp_sequ_entry udp_comb_entry
@@ -2094,41 +2094,41 @@ module_item
      statements in the task body. But we continue to accept it as an
      extension. */
 
-  | K_task IDENTIFIER ';'
+  | K_task automatic_opt IDENTIFIER ';'
       { assert(current_task == 0);
-	current_task = pform_push_task_scope($2);
+	current_task = pform_push_task_scope($3, $2);
 	FILE_NAME(current_task, @1);
       }
     task_item_list_opt
     statement_or_null
     K_endtask
-      { current_task->set_ports($5);
-	current_task->set_statement($6);
+      { current_task->set_ports($6);
+	current_task->set_statement($7);
 	pform_pop_scope();
 	current_task = 0;
-	delete[]$2;
+	delete[]$3;
       }
 
-  | K_task IDENTIFIER
+  | K_task automatic_opt IDENTIFIER
       { assert(current_task == 0);
-	current_task = pform_push_task_scope($2);
+	current_task = pform_push_task_scope($3, $2);
 	FILE_NAME(current_task, @1);
       }
     '(' task_port_decl_list ')' ';'
     block_item_decls_opt
     statement_or_null
     K_endtask
-      { current_task->set_ports($5);
-	current_task->set_statement($9);
+      { current_task->set_ports($6);
+	current_task->set_statement($10);
 	pform_pop_scope();
 	current_task = 0;
-	delete[]$2;
+	delete[]$3;
       }
-  | K_task IDENTIFIER error K_endtask
+  | K_task automatic_opt IDENTIFIER error K_endtask
       {
 	pform_pop_scope();
 	current_task = 0;
-	delete[]$2;
+	delete[]$3;
       }
 
   /* The function declaration rule matches the function declaration
@@ -2136,42 +2136,42 @@ module_item
      definitions in the func_body to take on the scope of the function
      instead of the module. */
 
-  | K_function function_range_or_type_opt IDENTIFIER ';'
+  | K_function automatic_opt function_range_or_type_opt IDENTIFIER ';'
       { assert(current_function == 0);
-	current_function = pform_push_function_scope($3);
+	current_function = pform_push_function_scope($4, $2);
 	FILE_NAME(current_function, @1);
       }
     function_item_list statement
     K_endfunction
-      { current_function->set_ports($6);
-	current_function->set_statement($7);
-	current_function->set_return($2);
+      { current_function->set_ports($7);
+	current_function->set_statement($8);
+	current_function->set_return($3);
 	pform_pop_scope();
 	current_function = 0;
-	delete[]$3;
+	delete[]$4;
       }
 
-  | K_function function_range_or_type_opt IDENTIFIER
+  | K_function automatic_opt function_range_or_type_opt IDENTIFIER
       { assert(current_function == 0);
-	current_function = pform_push_function_scope($3);
+	current_function = pform_push_function_scope($4, $2);
 	FILE_NAME(current_function, @1);
       }
     '(' task_port_decl_list ')' ';'
     block_item_decls_opt
     statement
     K_endfunction
-      { current_function->set_ports($6);
-	current_function->set_statement($10);
-	current_function->set_return($2);
+      { current_function->set_ports($7);
+	current_function->set_statement($11);
+	current_function->set_return($3);
 	pform_pop_scope();
 	current_function = 0;
-	delete[]$3;
+	delete[]$4;
       }
-  | K_function function_range_or_type_opt IDENTIFIER error K_endfunction
+  | K_function automatic_opt function_range_or_type_opt IDENTIFIER error K_endfunction
       {
 	pform_pop_scope();
 	current_task = 0;
-	delete[]$3;
+	delete[]$4;
       }
 
   /* A generate region can contain further module items. Actually, it
@@ -2278,6 +2278,11 @@ module_item
 		{ yyerror(@1, "error: Malformed $attribute parameter list."); }
 	;
 
+automatic_opt
+	: K_automatic { $$ = true; }
+	| { $$ = false;}
+	;
+
 generate_if : K_if '(' expression ')' { pform_start_generate_if(@1, $3); }
 
 generate_case_items
diff --git a/pform.cc b/pform.cc
index 6b3612a06..7057376cc 100644
--- a/pform.cc
+++ b/pform.cc
@@ -103,17 +103,18 @@ void pform_pop_scope()
       }
 }
 
-PTask* pform_push_task_scope(char*name)
+PTask* pform_push_task_scope(char*name, bool is_auto)
 {
       perm_string task_name = lex_strings.make(name);
 
       PTask*task;
       if (pform_cur_generate) {
-	    task = new PTask(task_name, pform_cur_generate->lexical_scope);
+	    task = new PTask(task_name, pform_cur_generate->lexical_scope,
+	                     is_auto);
 	    pform_cur_generate->tasks[task->pscope_name()] = task;
 	    pform_cur_generate->lexical_scope = task;
       } else {
-	    task = new PTask(task_name, lexical_scope);
+	    task = new PTask(task_name, lexical_scope, is_auto);
 	    pform_cur_module->tasks[task->pscope_name()] = task;
 	    lexical_scope = task;
       }
@@ -121,17 +122,18 @@ PTask* pform_push_task_scope(char*name)
       return task;
 }
 
-PFunction* pform_push_function_scope(char*name)
+PFunction* pform_push_function_scope(char*name, bool is_auto)
 {
       perm_string func_name = lex_strings.make(name);
 
       PFunction*func;
       if (pform_cur_generate) {
-	    func = new PFunction(func_name, pform_cur_generate->lexical_scope);
+	    func = new PFunction(func_name, pform_cur_generate->lexical_scope,
+	                         is_auto);
 	    pform_cur_generate->funcs[func->pscope_name()] = func;
 	    pform_cur_generate->lexical_scope = func;
       } else {
-	    func = new PFunction(func_name, lexical_scope);
+	    func = new PFunction(func_name, lexical_scope, is_auto);
 	    pform_cur_module->funcs[func->pscope_name()] = func;
 	    lexical_scope = func;
       }
diff --git a/pform.h b/pform.h
index a94be9f96..ae410c8e7 100644
--- a/pform.h
+++ b/pform.h
@@ -175,8 +175,8 @@ extern void pform_make_udp(perm_string name,
  */
 extern void pform_pop_scope();
 
-extern PTask*pform_push_task_scope(char*name);
-extern PFunction*pform_push_function_scope(char*name);
+extern PTask*pform_push_task_scope(char*name, bool is_auto);
+extern PFunction*pform_push_function_scope(char*name, bool is_auto);
 extern PBlock*pform_push_block_scope(char*name, PBlock::BL_TYPE tt);
 
 
diff --git a/pform_dump.cc b/pform_dump.cc
index ba6e60912..f506bd655 100644
--- a/pform_dump.cc
+++ b/pform_dump.cc
@@ -715,6 +715,7 @@ void PForStatement::dump(ostream&out, unsigned ind) const
 void PFunction::dump(ostream&out, unsigned ind) const
 {
       out << setw(ind) << "" << "function ";
+      if (is_auto_) cout << "automatic ";
       switch (return_type_.type) {
 	  case PTF_NONE:
 	    out << "?none? ";
@@ -775,6 +776,9 @@ void PRepeat::dump(ostream&out, unsigned ind) const
 
 void PTask::dump(ostream&out, unsigned ind) const
 {
+      out << setw(ind) << "" << "task ";
+      if (is_auto_) cout << "automatic ";
+      out << pscope_name() << ";" << endl;
       if (ports_)
 	    for (unsigned idx = 0 ;  idx < ports_->count() ;  idx += 1) {
 		  out << setw(ind) << "";
diff --git a/t-dll-api.cc b/t-dll-api.cc
index e9db3bf5e..379053b45 100644
--- a/t-dll-api.cc
+++ b/t-dll-api.cc
@@ -1547,6 +1547,12 @@ extern "C" const char*ivl_scope_file(ivl_scope_t net)
       return net->file.str();
 }
 
+extern "C" unsigned ivl_scope_is_auto(ivl_scope_t net)
+{
+      assert(net);
+      return net->is_auto;
+}
+
 extern "C" unsigned ivl_scope_lineno(ivl_scope_t net)
 {
       assert(net);
diff --git a/t-dll.cc b/t-dll.cc
index e11692145..98ade6c15 100644
--- a/t-dll.cc
+++ b/t-dll.cc
@@ -575,6 +575,7 @@ void dll_target::add_root(ivl_design_s &des_, const NetScope *s)
       root_->time_units = s->time_unit();
       root_->nattr = s->attr_cnt();
       root_->attr  = fill_in_attributes(s);
+      root_->is_auto = 0;
 
       des_.nroots_++;
       if (des_.roots_)
@@ -2319,7 +2320,8 @@ void dll_target::scope(const NetScope*net)
 	    scope->time_precision = net->time_precision();
 	    scope->time_units = net->time_unit();
 	    scope->nattr = net->attr_cnt();
-	    scope->attr  = fill_in_attributes(net);
+	    scope->attr = fill_in_attributes(net);
+	    scope->is_auto = net->is_auto();
 
 	    switch (net->type()) {
 		case NetScope::MODULE:
diff --git a/t-dll.h b/t-dll.h
index c409a6ce9..f5d6fd4b7 100644
--- a/t-dll.h
+++ b/t-dll.h
@@ -590,6 +590,7 @@ struct ivl_scope_s {
 
 	/* Scopes that are tasks/functions have a definition. */
       ivl_statement_t def;
+      unsigned is_auto;
 
       unsigned ports;
       ivl_signal_t*port;
diff --git a/tgt-stub/stub.c b/tgt-stub/stub.c
index 927312765..aba418c14 100644
--- a/tgt-stub/stub.c
+++ b/tgt-stub/stub.c
@@ -1448,12 +1448,13 @@ static int show_scope(ivl_scope_t net, void*x)
 	      ivl_scope_name(net), ivl_scope_params(net),
 	      ivl_scope_sigs(net), ivl_scope_logs(net));
 
+      char *is_auto = ivl_scope_is_auto(net) ? "automatic " : "";
       switch (ivl_scope_type(net)) {
 	  case IVL_SCT_MODULE:
 	    fprintf(out, " module %s", ivl_scope_tname(net));
 	    break;
 	  case IVL_SCT_FUNCTION:
-	    fprintf(out, " function %s", ivl_scope_tname(net));
+	    fprintf(out, " function %s%s", is_auto, ivl_scope_tname(net));
 	    break;
 	  case IVL_SCT_BEGIN:
 	    fprintf(out, " begin : %s", ivl_scope_tname(net));
@@ -1462,7 +1463,7 @@ static int show_scope(ivl_scope_t net, void*x)
 	    fprintf(out, " fork : %s", ivl_scope_tname(net));
 	    break;
 	  case IVL_SCT_TASK:
-	    fprintf(out, " task %s", ivl_scope_tname(net));
+	    fprintf(out, " task %s%s", is_auto, ivl_scope_tname(net));
 	    break;
 	  default:
 	    fprintf(out, " type(%u) %s", ivl_scope_type(net),
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index 42f378711..433263b24 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -1769,6 +1769,13 @@ int draw_scope(ivl_scope_t net, ivl_scope_t parent)
 {
       unsigned idx;
       const char *type;
+	/* For now we do not support automatic tasks or functions. */
+      if (ivl_scope_is_auto(net)) {
+	    fprintf(stderr, "%s:%u: vvp-tgt sorry: automatic tasks/functions "
+	                    "are not supported!\n",
+	                    ivl_scope_def_file(net), ivl_scope_def_lineno(net));
+	    exit(1);
+      }
       switch (ivl_scope_type(net)) {
       case IVL_SCT_MODULE:   type = "module";   break;
       case IVL_SCT_FUNCTION: type = "function"; break;
diff --git a/verinum.cc b/verinum.cc
index 87f28de04..b4f20f32e 100644
--- a/verinum.cc
+++ b/verinum.cc
@@ -152,6 +152,112 @@ verinum::verinum(uint64_t val, unsigned n)
       }
 }
 
+/* The second argument is not used! It is there to make this
+ * constructor unique. */
+verinum::verinum(double val, bool dummy)
+: has_len_(false), has_sign_(true), string_flag_(false)
+{
+      bool is_neg = false;
+      double fraction;
+      int exponent;
+      const unsigned BITS_IN_LONG = 8*sizeof(long);
+
+	/* We return `bx for a NaN or +/- infinity. */
+      if (val != val || (val && (val == 0.5*val))) {
+	    nbits_ = 1;
+	    bits_ = new V[nbits_];
+	    bits_[0] = Vx;
+	    return;
+      }
+
+	/* Convert to a positive result. */
+      if (val < 0.0) {
+	    is_neg = true;
+	    val = -val;
+      }
+
+	/* Get the exponent and fractional part of the number. */
+      fraction = frexp(val, &exponent);
+      nbits_ = exponent+1;
+      bits_ = new V[nbits_];
+      const verinum const_one(1);
+
+	/* If the value is small enough just use lround(). */
+      if (nbits_ <= BITS_IN_LONG) {
+	    long sval = lround(val);
+	    if (is_neg) sval = -sval;
+	    for (unsigned idx = 0; idx < nbits_; idx += 1) {
+		  bits_[idx] = (sval&1) ? V1 : V0;
+		  sval >>= 1;
+	    }
+	      /* Trim the result. */
+	    signed_trim();
+	    return;
+      }
+
+      unsigned nwords = (exponent-1)/BITS_IN_LONG;
+
+      fraction = ldexp(fraction, (exponent-1) % BITS_IN_LONG + 1);
+
+      if (nwords == 0) {
+	    unsigned long bits = (unsigned long) fraction;
+	    fraction = fraction - (double) bits;
+	    for (unsigned idx = 0; idx < nbits_; idx += 1) {
+		  bits_[idx] = (bits&1) ? V1 : V0;
+		  bits >>= 1;
+	    }
+	    if (fraction >= 0.5) *this = *this + const_one;
+      } else {
+	    for (int wd = nwords; wd >= 0; wd -= 1) {
+		  unsigned long bits = (unsigned long) fraction;
+		  fraction = fraction - (double) bits;
+		  unsigned max = (wd+1)*BITS_IN_LONG;
+		  if (max > nbits_) max = nbits_;
+		  for (unsigned idx = wd*BITS_IN_LONG; idx < max; idx += 1) {
+			bits_[idx] = (bits&1) ? V1 : V0;
+			bits >>= 1;
+		  }
+		  fraction = ldexp(fraction, BITS_IN_LONG);
+	    }
+	    if (fraction >= ldexp(0.5, BITS_IN_LONG)) *this = *this + const_one;
+      }
+
+	/* Convert a negative number if needed. */
+      if (is_neg) {
+	    *this = v_not(*this) + const_one;
+      }
+
+	/* Trim the result. */
+      signed_trim();
+}
+
+
+/* This is used by the double constructor above. It is needed to remove
+ * extra sign bits that can occur when calculating a negative value. */
+void verinum::signed_trim()
+{
+	/* Do we have any extra digits? */
+      unsigned tlen = nbits_-1;
+      verinum::V sign = bits_[tlen];
+      while ((tlen > 0) && (bits_[tlen] == sign)) tlen -= 1;
+
+	/* tlen now points to the first digit that is not the sign.
+	 * or bit 0. Set the length to include this bit and one proper
+	 * sign bit if needed. */
+      if (bits_[tlen] != sign) tlen += 1;
+      tlen += 1;
+
+	/* Trim the bits if needed. */
+      if (tlen < nbits_) {
+	    V* tbits = new V[tlen];
+	    for (unsigned idx = 0; idx < tlen; idx += 1)
+		  tbits[idx] = bits_[idx];
+	    delete[] bits_;
+	    bits_ = tbits;
+	    nbits_ = tlen;
+      }
+}
+
 verinum::verinum(const verinum&that)
 {
       string_flag_ = that.string_flag_;
@@ -336,14 +442,9 @@ double verinum::as_double() const
 {
       if (nbits_ == 0) return 0.0;
 
-        /* Do we have a signed value? */
-      bool signed_flag = false;
-      if (bits_[nbits_-1] == V1) {
-	    signed_flag = true;
-      }
-
       double val = 0.0;
-      if (signed_flag) {
+        /* Do we have/want a signed value? */
+      if (has_sign_ && bits_[nbits_-1] == V1) {
 	    V carry = V1;
 	    for (unsigned idx = 0; idx < nbits_; idx += 1) {
 		  V sum = add_with_carry(~bits_[idx], V0, carry);
@@ -351,7 +452,6 @@ double verinum::as_double() const
 			val += pow(2.0, (double)idx);
 	    }
 	    val *= -1.0;
-//	    val = (double) as_long();
       } else {
 	    for (unsigned idx = 0; idx < nbits_; idx += 1) {
 		  if (bits_[idx] == V1)
diff --git a/verinum.h b/verinum.h
index b184c3c8c..5142883ee 100644
--- a/verinum.h
+++ b/verinum.h
@@ -46,6 +46,7 @@ class verinum {
       verinum(const V*v, unsigned nbits, bool has_len =true);
       verinum(V, unsigned nbits =1, bool has_len =true);
       verinum(uint64_t val, unsigned bits);
+      verinum(double val, bool dummy);
       verinum(const verinum&);
 
 	// Create a signed number, with an unspecified number of bits.
@@ -93,6 +94,8 @@ class verinum {
       signed long   as_long() const;
       double as_double() const;
       string as_string() const;
+    private:
+      void signed_trim();
 
     private:
       V* bits_;
diff --git a/vpi/Makefile.in b/vpi/Makefile.in
index f9b28a57d..a2b8bea94 100644
--- a/vpi/Makefile.in
+++ b/vpi/Makefile.in
@@ -60,7 +60,7 @@ sys_finish.o sys_icarus.o sys_plusargs.o sys_random.o sys_random_mti.o \
 sys_readmem.o sys_readmem_lex.o sys_scanf.o sys_sdf.o \
 sys_time.o sys_vcd.o sys_vcdoff.o vcd_priv.o \
 mt19937int.o sys_priv.o sdf_lexor.o sdf_parse.o stringheap.o \
-vams_simparam.o
+sys_clog2.o vams_simparam.o
 
 ifeq (@HAVE_LIBZ@,yes)
 ifeq (@HAVE_LIBBZ2@,yes)
diff --git a/vpi/sys_clog2.c b/vpi/sys_clog2.c
new file mode 100644
index 000000000..043e44fd0
--- /dev/null
+++ b/vpi/sys_clog2.c
@@ -0,0 +1,109 @@
+/*
+ *  Copyright (C) 2008  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
+ *  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.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <assert.h>
+#include <math.h>
+#include <string.h>
+#include <vpi_user.h>
+#include "sys_priv.h"
+
+/*
+ * Check that the function is called with the correct argument.
+ */
+static PLI_INT32 sys_clog2_compiletf(PLI_BYTE8 *name)
+{
+      vpiHandle callh = vpi_handle(vpiSysTfCall, 0);
+      assert(callh != 0);
+      vpiHandle argv = vpi_iterate(vpiArgument, callh);
+      vpiHandle arg;
+      (void) name;  // Not used!
+
+	/* We must have an argument. */
+      if (argv == 0) {
+	    vpi_printf("ERROR: %s line %d: ", vpi_get_str(vpiFile, callh),
+	               (int)vpi_get(vpiLineNo, callh));
+	    vpi_printf("$clog2 requires one numeric argument.\n");
+	    vpi_control(vpiFinish, 1);
+	    return 0;
+      }
+
+	/* The argument must be numeric. */
+      arg = vpi_scan(argv);
+      if (! is_numeric_obj(arg)) {
+	    vpi_printf("ERROR: %s line %d: ", vpi_get_str(vpiFile, callh),
+	               (int)vpi_get(vpiLineNo, callh));
+	    vpi_printf("The first argument to $clog2 must be numeric.\n");
+	    vpi_control(vpiFinish, 1);
+      }
+
+	/* We can have a maximum of one argument. */
+      if (vpi_scan(argv) != 0) {
+	    char msg [64];
+	    snprintf(msg, 64, "ERROR: %s line %d:",
+	             vpi_get_str(vpiFile, callh),
+	             (int)vpi_get(vpiLineNo, callh));
+
+	    unsigned argc = 1;
+	    while (vpi_scan(argv)) argc += 1;
+
+            vpi_printf("%s $clog2 takes at most one argument.\n", msg);
+            vpi_printf("%*s Found %u extra argument%s.\n",
+	               strlen(msg), " ", argc, argc == 1 ? "" : "s");
+            vpi_control(vpiFinish, 1);
+      }
+
+      return 0;
+}
+
+static PLI_INT32 sys_clog2_calltf(PLI_BYTE8 *name)
+{
+      vpiHandle callh = vpi_handle(vpiSysTfCall, 0);
+      vpiHandle argv = vpi_iterate(vpiArgument, callh);
+      vpiHandle arg;
+      s_vpi_value val;
+      s_vpi_vecval vec;
+      (void) name;  // Not used!/
+
+	/* Get the argument. */
+      arg = vpi_scan(argv);
+      vpi_free_object(argv);
+
+      vec = vpip_calc_clog2(arg);
+
+      val.format = vpiVectorVal;
+      val.value.vector = &vec;
+      vpi_put_value(callh, &val, 0, vpiNoDelay);
+      return 0;
+}
+
+/*
+ * Register the function with Verilog.
+ */
+void sys_clog2_register(void)
+{
+      s_vpi_systf_data tf_data;
+
+      tf_data.type        = vpiSysFunc;
+      tf_data.sysfunctype = vpiIntFunc;
+      tf_data.calltf      = sys_clog2_calltf;
+      tf_data.compiletf   = sys_clog2_compiletf;
+      tf_data.sizetf      = 0;
+      tf_data.tfname      = "$clog2";
+      tf_data.user_data   = 0;
+      vpi_register_systf(&tf_data);
+}
diff --git a/vpi/sys_table.c b/vpi/sys_table.c
index 4560744e7..56d480217 100644
--- a/vpi/sys_table.c
+++ b/vpi/sys_table.c
@@ -38,6 +38,7 @@ extern void sys_time_register();
 extern void sys_vcd_register();
 extern void sys_vcdoff_register();
 extern void sys_special_register();
+extern void sys_clog2_register();
 extern void vams_simparam_register();
 
 #ifdef HAVE_LIBZ
@@ -181,6 +182,7 @@ void (*vlog_startup_routines[])() = {
       sys_lxt_or_vcd_register,
       sys_sdf_register,
       sys_special_register,
+      sys_clog2_register,
       vams_simparam_register,
       0
 };
diff --git a/vpi/system.sft b/vpi/system.sft
index d6ff0a311..75abe1bdc 100644
--- a/vpi/system.sft
+++ b/vpi/system.sft
@@ -14,6 +14,7 @@ $dist_poisson      vpiSysFuncInt
 $dist_chi_square   vpiSysFuncInt
 $dist_t            vpiSysFuncInt
 $dist_erlang       vpiSysFuncInt
+$clog2             vpiSysFuncInt
 
 $simparam      vpiSysFuncReal
 $simparam$str  vpiSysFuncSized 1024 unsigned
diff --git a/vpi_user.h b/vpi_user.h
index 72b10c6c6..19d128cf8 100644
--- a/vpi_user.h
+++ b/vpi_user.h
@@ -566,6 +566,7 @@ extern DLLEXPORT void (*vlog_startup_routines[])();
      buffer. The value must be a vpiStrengthVal. */
 extern void vpip_format_strength(char*str, s_vpi_value*value, unsigned bit);
 extern void vpip_set_return_value(int value);
+extern s_vpi_vecval vpip_calc_clog2(vpiHandle arg);
 
 EXTERN_C_END
 
diff --git a/vvp/vpi_callback.cc b/vvp/vpi_callback.cc
index 931d92d39..db8cf64b1 100644
--- a/vvp/vpi_callback.cc
+++ b/vvp/vpi_callback.cc
@@ -127,6 +127,12 @@ static struct __vpiCallback* make_value_change(p_cb_data data)
 	    obj->cb_time.type = vpiSuppressTime;
       }
       obj->cb_data.time = &obj->cb_time;
+      if (data->value) {
+	    obj->cb_value = *(data->value);
+      } else {
+	    obj->cb_value.format = vpiSuppressVal;
+      }
+      obj->cb_data.value = &obj->cb_value;
 
       assert(data->obj);
       assert(data->obj->vpi_type);
@@ -457,8 +463,25 @@ void callback_execute(struct __vpiCallback*cur)
       vpi_mode_flag = VPI_MODE_RWSYNC;
 
       assert(cur->cb_data.cb_rtn);
-      cur->cb_data.time->type = vpiSimTime;
-      vpip_time_to_timestruct(cur->cb_data.time, schedule_simtime());
+      switch (cur->cb_data.time->type) {
+	  case vpiSimTime:
+	    vpip_time_to_timestruct(cur->cb_data.time, schedule_simtime());
+	    break;
+	  case vpiScaledRealTime: {
+	    cur->cb_data.time->real =
+	         vpip_time_to_scaled_real(schedule_simtime(),
+	             (struct __vpiScope *) vpi_handle(vpiScope,
+	                                              cur->cb_data.obj));
+	    break;
+	  }
+	  case vpiSuppressTime:
+	    break;
+	  default:
+	    fprintf(stderr, "Unsupported time format %d.\n",
+	            cur->cb_data.time->type);
+	    assert(0);
+	    break;
+      }
       (cur->cb_data.cb_rtn)(&cur->cb_data);
 
       vpi_mode_flag = save_mode;
@@ -546,10 +569,32 @@ void vvp_fun_signal::get_value(struct t_vpi_value*vp)
 {
       switch (vp->format) {
 	  case vpiScalarVal:
+	    // This works because vvp_bit4_t has the same encoding
+	    // as a scalar value! See vpip_vec4_get_value() for a 
+	    // more robust method.
 	    vp->value.scalar = value(0);
 	    break;
+
+	  case vpiBinStrVal:
+	  case vpiOctStrVal:
+	  case vpiDecStrVal:
+	  case vpiHexStrVal:
+	  case vpiIntVal:
+	  case vpiVectorVal:
+	  case vpiStringVal:
+	  case vpiRealVal: {
+	    unsigned wid = size();
+	    vvp_vector4_t vec4(wid);
+	    for (unsigned idx = 0; idx < wid; idx += 1) {
+		  vec4.set_bit(idx, value(idx));
+	    }
+	    vpip_vec4_get_value(vec4, wid, false, vp);
+	    break;
+	  }
+
 	  case vpiSuppressVal:
 	    break;
+
 	  default:
 	    fprintf(stderr, "vpi_callback: value "
 		    "format %d not supported (fun_signal)\n",
@@ -622,6 +667,9 @@ void vvp_fun_signal_real::get_value(struct t_vpi_value*vp)
 		break;
 	  }
 
+	  case vpiSuppressVal:
+	    break;
+
 	  default:
 	    fprintf(stderr, "vpi_callback: value "
 		    "format %d not supported (fun_signal_real)\n",
diff --git a/vvp/vpi_priv.cc b/vvp/vpi_priv.cc
index 0c004d2a9..d7a897604 100644
--- a/vvp/vpi_priv.cc
+++ b/vvp/vpi_priv.cc
@@ -456,6 +456,13 @@ void vpip_vec4_get_value(const vvp_vector4_t&word_val, unsigned width,
 		    vp->format);
 	    assert(0 && "format not implemented");
 
+	  case vpiObjTypeVal:
+	    vp->format = vpiVectorVal;
+	    break;
+
+	  case vpiSuppressVal:
+	    break;
+
 	  case vpiBinStrVal:
 	    rbuf = need_result_buf(width+1, RBUF_VAL);
 	    for (unsigned idx = 0 ;  idx < width ;  idx += 1) {
@@ -504,6 +511,7 @@ void vpip_vec4_get_value(const vvp_vector4_t&word_val, unsigned width,
                       break;
 	            case BIT4_X:
                       vp->value.scalar = vpiX;
+                      break;
 	            case BIT4_Z:
                       vp->value.scalar = vpiZ;
                       break;
@@ -1029,3 +1037,63 @@ extern "C" void vpi_control(PLI_INT32 operation, ...)
       vpi_sim_vcontrol(operation, ap);
       va_end(ap);
 }
+
+/*
+ * This routine calculated the return value for $clog2.
+ * It is easier to do it here vs trying to to use the VPI interface.
+ */
+extern "C" s_vpi_vecval vpip_calc_clog2(vpiHandle arg)
+{
+      s_vpi_vecval rtn;
+      s_vpi_value val;
+      vvp_vector4_t vec4;
+      bool is_neg = false;  // At this point only a real can be negative.
+
+	/* Get the value as a vvp_vector4_t. */
+      val.format = vpiObjTypeVal;
+      vpi_get_value(arg, &val);
+      if (val.format == vpiRealVal) {
+	    vpi_get_value(arg, &val);
+	      /* All double values can be represented in 1024 bits. */
+	    vec4 = vvp_vector4_t(1024, val.value.real);
+	    if (val.value.real < 0) is_neg = true;
+      } else {
+	    val.format = vpiVectorVal;
+	    vpi_get_value(arg, &val);
+	    unsigned wid = vpi_get(vpiSize, arg);
+	    vec4 = vvp_vector4_t(wid, BIT4_0);
+	    for (unsigned idx=0; idx < wid; idx += 1) {
+		PLI_INT32 aval = val.value.vector[idx/32].aval;
+		PLI_INT32 bval = val.value.vector[idx/32].bval;
+		aval >>= idx % 32;
+		bval >>= idx % 32;
+		int bitmask = (aval&1) | ((bval<<1)&2);
+		vvp_bit4_t bit = scalar_to_bit4(bitmask);
+		vec4.set_bit(idx, bit);
+	    }
+      }
+
+      if (vec4.has_xz()) {
+	    rtn.aval = rtn.bval = 0xFFFFFFFFU;  /* Set to 'bx. */
+	    return rtn;
+      }
+
+      vvp_vector2_t vec2(vec4);
+
+      if (is_neg) vec2.trim_neg(); /* This is a special trim! */
+      else vec2.trim(); /* This makes less work shifting. */
+
+	/* Calculate the clog2 result. */
+      PLI_INT32 res = 0;
+      if (!vec2.is_zero()) {
+	    vec2 -= vvp_vector2_t(1, vec2.size());
+	    while(!vec2.is_zero()) {
+		  res += 1;
+		  vec2 >>= 1;
+	    }
+      }
+
+      rtn.aval = res;
+      rtn.bval = 0;
+      return rtn;
+}
diff --git a/vvp/vpi_priv.h b/vvp/vpi_priv.h
index 25a5282b8..49d38ed5d 100644
--- a/vvp/vpi_priv.h
+++ b/vvp/vpi_priv.h
@@ -137,6 +137,7 @@ struct __vpiCallback {
 	// user supplied callback data
       struct t_cb_data cb_data;
       struct t_vpi_time cb_time;
+      struct t_vpi_value cb_value;
 
 	// scheduled event
       struct sync_cb* cb_sync;
diff --git a/vvp/vpi_signal.cc b/vvp/vpi_signal.cc
index eacbf1732..cea4c9882 100644
--- a/vvp/vpi_signal.cc
+++ b/vvp/vpi_signal.cc
@@ -728,23 +728,6 @@ static vvp_vector4_t from_stringval(const char*str, unsigned wid)
       return val;
 }
 
-static vvp_bit4_t scalar_to_bit4(PLI_INT32 scalar)
-{
-      switch(scalar) {
-	  case vpi0:
-	    return BIT4_0;
-	  case vpi1:
-	    return BIT4_1;
-	  case vpiX:
-	    return BIT4_X;
-	  case vpiZ:
-	    return BIT4_Z;
-	  default:
-	    fprintf(stderr, "Unsupported scalar value %d.\n", scalar);
-	    assert(0);
-      }
-}
-
 static vpiHandle signal_put_value(vpiHandle ref, s_vpi_value*vp, int flags)
 {
       unsigned wid;
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index 2703bccb0..373afefca 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -2071,7 +2071,14 @@ bool of_FORK(vthread_t thr, vvp_code_t cp)
 
       thr->fork_count += 1;
 
-      schedule_vthread(child, 0, true);
+	/* If the new child was created to evaluate a function,
+	   run it immediately, then return to this thread. */
+      if (cp->scope->base.vpi_type->type_code == vpiFunction) {
+	    child->is_scheduled = 1;
+	    vthread_run(child);
+      } else {
+	    schedule_vthread(child, 0, true);
+      }
       return true;
 }
 
diff --git a/vvp/vvp.def b/vvp/vvp.def
index ad3990f05..1ec96567d 100644
--- a/vvp/vvp.def
+++ b/vvp/vvp.def
@@ -37,3 +37,4 @@ vpi_vprintf
 
 vpip_format_strength
 vpip_set_return_value
+vpip_calc_clog2
diff --git a/vvp/vvp_net.cc b/vvp/vvp_net.cc
index d922bb77d..5719f068f 100644
--- a/vvp/vvp_net.cc
+++ b/vvp/vvp_net.cc
@@ -130,6 +130,23 @@ vvp_bit4_t add_with_carry(vvp_bit4_t a, vvp_bit4_t b, vvp_bit4_t&c)
       }
 }
 
+vvp_bit4_t scalar_to_bit4(PLI_INT32 scalar)
+{
+      switch(scalar) {
+	  case vpi0:
+	    return BIT4_0;
+	  case vpi1:
+	    return BIT4_1;
+	  case vpiX:
+	    return BIT4_X;
+	  case vpiZ:
+	    return BIT4_Z;
+	  default:
+	    fprintf(stderr, "Unsupported scalar value %d.\n", scalar);
+	    assert(0);
+      }
+}
+
 vvp_bit4_t operator ^ (vvp_bit4_t a, vvp_bit4_t b)
 {
       if (bit4_is_xz(a))
@@ -372,19 +389,12 @@ vvp_vector4_t::vvp_vector4_t(unsigned size, double val)
       double fraction;
       int exponent;
 
-	/* We return 'bx for a NaN. */
-      if (val != val)  {
+	/* We return 'bx for a NaN or +/- infinity. */
+      if (val != val || (val && (val == 0.5*val)))  {
 	    allocate_words_(size, WORD_X_ABITS, WORD_X_BBITS);
 	    return;
       }
 
-	/* We return 'b1 for + infinity or 'b0 for - infinity. */
-      if (val && (val == 0.5*val)) {
-	    if (val > 0) allocate_words_(size, WORD_1_ABITS, WORD_1_BBITS);
-	    else allocate_words_(size, WORD_0_ABITS, WORD_0_BBITS);
-	    return;
-      }
-
 	/* Convert to a positive result. */
       if (val < 0.0) {
 	    is_neg = true;
@@ -1618,6 +1628,15 @@ void vvp_vector2_t::trim()
       while (value(wid_-1) == 0 && wid_ > 1) wid_ -= 1;
 }
 
+/* This is a special trim that is used on numbers we know represent a
+ * negative signed value (they came from a negative real value). */
+void vvp_vector2_t::trim_neg()
+{
+      if (value(wid_-1) == 1 && wid_ > 32) {
+	    while (value(wid_-2) == 1 && wid_ > 32) wid_ -= 1;
+      }
+}
+
 int vvp_vector2_t::value(unsigned idx) const
 {
       if (idx >= wid_)
diff --git a/vvp/vvp_net.h b/vvp/vvp_net.h
index 6e6497179..1297564e8 100644
--- a/vvp/vvp_net.h
+++ b/vvp/vvp_net.h
@@ -20,6 +20,7 @@
  */
 
 # include  "config.h"
+# include  "vpi_user.h"
 # include  <stddef.h>
 # include  <string.h>
 # include  <new>
@@ -67,6 +68,8 @@ inline char vvp_bit4_to_ascii(vvp_bit4_t a) { return "01zx"[a]; }
 
 extern vvp_bit4_t add_with_carry(vvp_bit4_t a, vvp_bit4_t b, vvp_bit4_t&c);
 
+extern vvp_bit4_t scalar_to_bit4(PLI_INT32 scalar);
+
   /* Return TRUE if the bit is BIT4_X or BIT4_Z. The fast
      implementation here relies on the encoding of vvp_bit4_t values. */
 inline bool bit4_is_xz(vvp_bit4_t a) { return a >= 2; }
@@ -470,6 +473,9 @@ class vvp_vector2_t {
       void set_bit(unsigned idx, int bit);
 	// Make the size just big enough to hold the first 1 bit.
       void trim();
+	// Trim off extra 1 bit since this is representing a negative value.
+	// Always keep at least 32 bits.
+      void trim_neg();
 
     private:
       enum { BITS_PER_WORD = 8 * sizeof(unsigned long) };