Add error when driving input-only modport.

Changes

@@ -10,6 +10,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Add data types to --xml. [Rui Terra]
 
+****  Add error when driving input-only modport.
+
 
 * Verilator 3.914 2017-10-14
 

src/V3LinkDot.cpp

@@ -1394,9 +1394,10 @@ class LinkDotIfaceVisitor : public AstNVisitor {
 	if (!symp) {
 	    nodep->v3error("Modport item not found: "<<nodep->prettyName());
 	} else if (AstVar* varp = symp->nodep()->castVar()) {
-	    // Make symbol under modport that points at the _interface_'s var, not the modport.
+	    // Make symbol under modport that points at the _interface_'s var via the modport.
+	    // (Need modport still to test input/output markings)
 	    nodep->varp(varp);
-	    m_statep->insertSym(m_curSymp, nodep->name(), varp, NULL/*package*/);
+	    m_statep->insertSym(m_curSymp, nodep->name(), nodep, NULL/*package*/);
 	} else if (AstVarScope* vscp = symp->nodep()->castVarScope()) {
 	    // Make symbol under modport that points at the _interface_'s var, not the modport.
 	    nodep->varp(vscp->varp());
@@ -1514,6 +1515,23 @@ private:
 	    m_statep->insertSym(moduleSymp, newp->name(), newp, NULL/*packagep*/);
 	}
     }
+    AstVar* foundToVarp(const VSymEnt* symp, AstNode* nodep, bool lvalue) {
+        // Return a variable if possible, auto converting a modport to variable
+        if (!symp) {
+            return NULL;
+        } else if (symp->nodep()->castVar()) {
+            return symp->nodep()->castVar();
+        } else if (symp->nodep()->castModportVarRef()) {
+            AstModportVarRef* snodep = symp->nodep()->castModportVarRef();
+            AstVar* varp = snodep->varp();
+            if (lvalue && snodep->isInput()) {
+                nodep->v3error("Attempt to drive input-only modport: "<<nodep->prettyName());
+            } // else other simulators don't warn about reading, and IEEE doesn't say illegal
+	    return varp;
+        } else {
+            return NULL;
+        }
+    }
     void taskFuncSwapCheck(AstNodeFTaskRef* nodep) {
 	if (nodep->taskp() && nodep->taskp()->castTask()
 	    && nodep->castFuncRef()) nodep->v3error("Illegal call of a task as a function: "<<nodep->prettyName());
@@ -1805,7 +1823,7 @@ private:
                     }
                 }
 	    }
-	    else if (AstVar* varp = foundp->nodep()->castVar()) {
+	    else if (AstVar* varp = foundToVarp(foundp, nodep, false)) {
 		AstIfaceRefDType* ifacerefp = LinkDotState::ifaceRefFromArray(varp->subDTypep());
 		if (ifacerefp) {
 		    if (!ifacerefp->ifaceViaCellp()) ifacerefp->v3fatalSrc("Unlinked interface");
@@ -1926,7 +1944,7 @@ private:
 	    UINFO(9," linkVarRef se"<<(void*)m_curSymp<<"  n="<<nodep<<endl);
 	    if (!m_curSymp) nodep->v3fatalSrc("NULL lookup symbol table");
 	    VSymEnt* foundp = m_curSymp->findIdFallback(nodep->name());
-	    if (AstVar* varp = foundp ? foundp->nodep()->castVar() : NULL) {
+	    if (AstVar* varp = foundp ? foundToVarp(foundp, nodep, nodep->lvalue()) : NULL) {
 		nodep->varp(varp);
 		nodep->packagep(foundp->packagep());  // Generally set by parse, but might be an import
 	    }
@@ -1960,7 +1978,7 @@ private:
 	    dotSymp = m_statep->findDotted(dotSymp, nodep->dotted(), baddot, okSymp); // Maybe NULL
 	    if (!m_statep->forScopeCreation()) {
 		VSymEnt* foundp = m_statep->findSymPrefixed(dotSymp, nodep->name(), baddot);
-		AstVar* varp = foundp ? foundp->nodep()->castVar() : NULL;
+		AstVar* varp = foundp ? foundToVarp(foundp, nodep, nodep->lvalue()) : NULL;
 		nodep->varp(varp);
 		UINFO(7,"         Resolved "<<nodep<<endl);  // Also prints varp
 		if (!nodep->varp()) {

src/V3Undriven.cpp

@@ -19,7 +19,7 @@
 //*************************************************************************
 // V3Undriven's Transformations:
 //
-// Each module:
+// Netlist:
 //      Make vector for all variables
 //	SEL(VARREF(...))) mark only some bits as used/driven
 //	else VARREF(...) mark all bits as used/driven
@@ -223,8 +223,11 @@ public:
 class UndrivenVisitor : public AstNVisitor {
 private:
     // NODE STATE
-    // AstVar::user1p		-> UndrivenVar* for usage var, 0=not set yet
+    // Netlist:
+    //  AstVar::user1p		-> UndrivenVar* for usage var, 0=not set yet
     AstUser1InUse	m_inuser1;
+    // Each always:
+    //  AstNode::user2p		-> UndrivenVar* for usage var, 0=not set yet
     AstUser2InUse	m_inuser2;
 
     // STATE

test_regress/t/t_lint_modport_dir_bad.pl

@@ -0,0 +1,24 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2008 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+#$Self->{vlt} or $Self->skip("Verilator only test");
+
+compile (
+    verilator_flags2 => ["--lint-only -Wno-DECLFILENAME"],
+    fails=>1,
+    verilator_make_gcc => 0,
+    make_top_shell => 0,
+    make_main => 0,
+    expect=>
+'%Error: t/t_lint_modport_dir_bad.v:\d+: Attempt to drive input-only modport: signal
+%Error: Exiting due to .*',
+    );
+
+ok(1);
+1;

test_regress/t/t_lint_modport_dir_bad.v

@@ -0,0 +1,49 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2017 by Wilson Snyder.
+
+interface dummy_if ();
+   logic signal;
+
+   modport slave
+     (output signal);
+
+   modport master
+     (input signal);
+endinterface: dummy_if
+
+module sub
+  (
+   input wire  signal_i,
+   output wire signal_o,
+
+   dummy_if.master dummy_in,
+   dummy_if.slave dummy_out
+   );
+
+   assign dummy_in.signal = signal_i;
+   assign signal_o = dummy_out.signal;
+endmodule
+
+
+module t (/*AUTOARG*/
+   // Outputs
+   signal_o,
+   // Inputs
+   signal_i
+   );
+   input signal_i;
+   output signal_o;
+
+   dummy_if dummy_if ();
+
+   sub sub
+     (
+      .signal_i(signal_i),
+      .signal_o(signal_o),
+      .dummy_in(dummy_if),
+      .dummy_out(dummy_if)
+      );
+
+endmodule