Fix false MULTITOP on bound interfaces (#4438).

Changes

@@ -21,6 +21,7 @@ Verilator 5.015 devel
 * Fix variable lifetimes in extern methods (#4414). [Krzysztof Boroński]
 * Fix multple function definitions in V3Sched (#4416). [Hennadii Chernyshchyk]
 * Fix false UNUSEDPARAM on generate localparam (#4427). [Bill Pringlemeir]
+* Fix false MULTITOP on bound interfaces (#4438). [Alex Solomatnikov]
 
 
 Verilator 5.014 2023-08-06

src/V3LinkLevel.cpp

@@ -53,7 +53,7 @@ void V3LinkLevel::modSortByLevel() {
     ModVec tops;  // Top level modules
     for (AstNodeModule* nodep = v3Global.rootp()->modulesp(); nodep;
          nodep = VN_AS(nodep->nextp(), NodeModule)) {
-        if (nodep->level() <= 2) tops.push_back(nodep);
+        if (nodep->level() <= 2 && !VN_IS(nodep, NotFoundModule)) tops.push_back(nodep);
         mods.push_back(nodep);
     }
     if (tops.size() >= 2) {

test_regress/t/t_bind_nfound.pl

@@ -0,0 +1,16 @@
+#!/usr/bin/env 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.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(linter => 1);
+
+lint();
+
+ok(1);
+1;

test_regress/t/t_bind_nfound.v

@@ -0,0 +1,27 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+interface bound_if;
+endinterface
+
+module t;
+
+   sub sub();
+
+   initial begin
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+
+endmodule
+
+module sub_ext;
+   bind sub_inst bound_if i_bound();
+endmodule
+
+module sub;
+   sub_ext sub_ext();
+endmodule