Add circular typedef error, bug1388.

Changes

@@ -9,6 +9,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  For --xml, add additional information, bug1372. [Jonathan Kimmitt]
 
+****  Add circular typedef error, bug1388.  [Al Grant]
+
 ****  Fix FST tracing of wide arrays, bug1376. [Aleksander Osman]
 
 ****  Fix error when pattern assignment has too few elements, bug1378. [Viktor Tomov]

src/V3AstNodes.cpp

@@ -929,8 +929,15 @@ void AstRange::dump(std::ostream& str) {
     if (littleEndian()) str<<" [LITTLE]";
 }
 void AstRefDType::dump(std::ostream& str) {
+    static bool s_recursing = false;
     this->AstNodeDType::dump(str);
-    if (defp()) { str<<" -> "; defp()->dump(str); }
+    if (defp()) {
+        if (!s_recursing) {  // Prevent infinite dump if circular typedefs
+            s_recursing = true;
+            str<<" -> "; defp()->dump(str);
+            s_recursing = false;
+        }
+    }
     else { str<<" -> UNLINKED"; }
 }
 void AstNodeClassDType::dump(std::ostream& str) {

src/V3Width.cpp

@@ -1043,12 +1043,24 @@ private:
 	UINFO(4,"dtWidthed "<<nodep<<endl);
     }
     virtual void visit(AstRefDType* nodep) {
-	if (nodep->didWidthAndSet()) return;  // This node is a dtype & not both PRELIMed+FINALed
-	userIterateChildren(nodep, NULL);
-	if (nodep->subDTypep()) nodep->refDTypep(iterateEditDTypep(nodep, nodep->subDTypep()));
-	nodep->dtypeFrom(nodep->dtypeSkipRefp());
-	nodep->widthFromSub(nodep->subDTypep());
-	UINFO(4,"dtWidthed "<<nodep<<endl);
+        if (nodep->doingWidth()) {  // Early exit if have circular parameter definition
+            nodep->v3error("Typedef's type is circular: "<<nodep->prettyName());
+            nodep->dtypeSetLogicBool();
+            nodep->doingWidth(false);
+            return;
+        }
+        if (nodep->didWidthAndSet()) return;  // This node is a dtype & not both PRELIMed+FINALed
+        nodep->doingWidth(true);
+        userIterateChildren(nodep, NULL);
+        if (nodep->subDTypep()) nodep->refDTypep(iterateEditDTypep(nodep, nodep->subDTypep()));
+        // Effectively nodep->dtypeFrom(nodep->dtypeSkipRefp());
+        // But might be recursive, so instead manually recurse into the referenced type
+        if (!nodep->defp()) nodep->v3fatalSrc("Unlinked");
+        nodep->dtypeFrom(nodep->defp());
+        userIterate(nodep->defp(), NULL);
+        nodep->widthFromSub(nodep->subDTypep());
+        UINFO(4,"dtWidthed "<<nodep<<endl);
+        nodep->doingWidth(false);
     }
     virtual void visit(AstTypedef* nodep) {
 	if (nodep->didWidthAndSet()) return;  // This node is a dtype & not both PRELIMed+FINALed

test_regress/t/t_typedef_circ_bad.out

@@ -0,0 +1,2 @@
+%Error: t/t_typedef_circ_bad.v:5: Typedef's type is circular: a_t
+%Error: Exiting due to

test_regress/t/t_typedef_circ_bad.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 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.
+
+scenarios(vlt_all => 1);
+
+compile(
+    v_flags2 => ["--lint-only"],
+    fails => $Self->{vlt_all},
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_typedef_circ_bad.v

@@ -0,0 +1,6 @@
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2019 by Wilson Snyder
+
+typedef a_t;
+typedef a_t b_t;
+typedef b_t a_t;