Fix UNDRIVEN warning seg fault (#3989)

Changes

@@ -61,6 +61,7 @@ Verilator 5.007 devel
 * Fix subsequent parameter declarations (#3969). [Ryszard Rozak, Antmicro Ltd]
 * Fix timing delays to not truncate below 64 bits (#3973) (#3982). [Felix Neumärker]
 * Fix cmake on macOS to mark weak symbols with -U linker flag (#3978) (#3979). [Peter Debacker]
+* Fix UNDRIVEN warning seg fault (#3989). [Felix Neumärker]
 * Fix packed array structure replication.
 * Fix enum.next(0) and enum.prev(0).
 

src/V3Undriven.cpp

@@ -408,7 +408,8 @@ private:
                 }
                 if (entryp->isDrivenWhole() && !m_inBBox && !VN_IS(nodep, VarXRef)
                     && !VN_IS(nodep->dtypep()->skipRefp(), UnpackArrayDType)
-                    && nodep->fileline() != entryp->getNodeFileLinep() && !entryp->isUnderGen()) {
+                    && nodep->fileline() != entryp->getNodeFileLinep() && !entryp->isUnderGen()
+                    && entryp->getNodep()) {
                     if (m_alwaysCombp
                         && (!entryp->isDrivenAlwaysCombWhole()
                             || (entryp->isDrivenAlwaysCombWhole()

test_regress/t/t_lint_always_comb_multidriven_compile_public_flat.pl

@@ -0,0 +1,22 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 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(vlt => 1);
+
+top_filename("t/t_lint_always_comb_multidriven.v");
+
+lint(
+    verilator_flags2 => ['--public-flat-rw --lint-only'],
+    fails => 1,
+    expect_filename => "t/t_lint_always_comb_multidriven.out",
+    );
+
+ok(1);
+1;