From d8141252e9828be3d52b5e0f9c5d3907a857b5ba Mon Sep 17 00:00:00 2001
From: steve <steve>
Date: Wed, 1 Aug 2001 05:17:31 +0000
Subject: [PATCH]  Accept empty port lists to module instantiation.

---
 elaborate.cc       | 24 ++++++++++++++++++--
 ieee1364-notes.txt | 55 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/elaborate.cc b/elaborate.cc
index a8c7b3636..9c42b0f44 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) && !defined(macintosh)
-#ident "$Id: elaborate.cc,v 1.218 2001/07/28 22:13:11 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.219 2001/08/01 05:17:31 steve Exp $"
 #endif
 
 # include "config.h"
@@ -481,11 +481,28 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, const string&path) const
 
 	    pins = exp;
 
+      } else if (pin_count() == 0) {
+
+	      /* Handle the special case that no ports are
+		 connected. It is possible that this is an empty
+		 connect-by-name list, su we'll allow it and assume
+		 that is the case. */
+
+	    svector<PExpr*>*tmp = new svector<PExpr*>(rmod->port_count());
+	    for (unsigned idx = 0 ;  idx < rmod->port_count() ;  idx += 1)
+		  (*tmp)[idx] = 0;
+
+	    pins = tmp;
+
       } else {
 
+	      /* Otherwise, this is a positional list of fort
+		 connections. In this case, the port count must be
+		 right. Check that is is, the get the pin list. */
+
 	    if (pin_count() != rmod->port_count()) {
 		  cerr << get_line() << ": error: Wrong number "
-			"of parameters. Expecting " << rmod->port_count() <<
+			"of ports. Expecting " << rmod->port_count() <<
 			", got " << pin_count() << "."
 		       << endl;
 		  des->errors += 1;
@@ -2345,6 +2362,9 @@ Design* elaborate(const map<string,Module*>&modules,
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.219  2001/08/01 05:17:31  steve
+ *  Accept empty port lists to module instantiation.
+ *
  * Revision 1.218  2001/07/28 22:13:11  steve
  *  Detect a missing task definition before it crashes me.
  *
diff --git a/ieee1364-notes.txt b/ieee1364-notes.txt
index addc9cb9a..3b5427ed9 100644
--- a/ieee1364-notes.txt
+++ b/ieee1364-notes.txt
@@ -268,8 +268,61 @@ comparison operators or the reduction operators. Icarus Verilog will
 generate appropriate error messages.
 
 
-$Id: ieee1364-notes.txt,v 1.7 2001/02/17 05:27:31 steve Exp $
+* MODULE INSTANCE WITH WRONG SIZE PORT LIST
+
+A module declaration like this declares a module that takes three ports:
+
+	module three (a, b, c);
+	  input a, b, c;
+	  reg x;
+	endmodule
+
+This is fine and obvious. It is also clear from the standard that
+these are legal instantiations of this module:
+
+	three u1 (x,y,z);
+	three u2 ( ,y, );
+	three u3 ( , , );
+	three u4 (.b(y));
+
+In some of the above examples, there are unconnected ports. In the
+case of u4, the pass by name connects only port b, and leaves a and c
+unconnected. u2 and u4 are the same thing, in fact, but using
+positional or by-name syntax. The next example is a little less
+obvious:
+
+	three u4 ();
+
+The trick here is that strictly speaking, the parser cannot tell
+whether this is a list of no pass by name ports (that is, all
+unconnected) or an empty positional list. If this were an empty
+positional list, then the wrong number of ports is given, but if it is
+an empty by-name list, it is an obviously valid instantiation. So it
+is fine to accept this case as valid.
+
+These are more doubtful:
+
+	three u5(x,y);
+	three u6(,);
+
+These are definitely positional port lists, and they are definitely
+the wrong length. In this case, the standard is not explicit about
+what to do about positional port lists in module instantiations,
+except that the first is connected to the first, second to second,
+etc. It does not say that the list must be the right length, but every
+example of unconnected ports used by-name syntax, and every example of
+ordered list has the right size list.
+
+Icarus Verilog takes the (very weak) hint that ordered lists should be
+the right length, and will therefore flag instances u5 and u6 as
+errors. The IEEE1364 standard should be more specific one way or the
+other.
+
+$Id: ieee1364-notes.txt,v 1.8 2001/08/01 05:17:31 steve Exp $
 $Log: ieee1364-notes.txt,v $
+Revision 1.8  2001/08/01 05:17:31  steve
+ Accept empty port lists to module instantiation.
+
 Revision 1.7  2001/02/17 05:27:31  steve
  I allow function ports to have types.