From 4a4db5ea6eed4399fe8e9707d8066449e88e4860 Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@klayout.de>
Date: Thu, 28 Dec 2023 00:55:05 +0100
Subject: [PATCH] [consider merging] Avoids a segfault

This happens when an expression returns a class
object and that is converted to a string.
---
 src/tl/tl/tlVariant.cc | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/tl/tl/tlVariant.cc b/src/tl/tl/tlVariant.cc
index 2360b9ee7..b25a6bbf8 100644
--- a/src/tl/tl/tlVariant.cc
+++ b/src/tl/tl/tlVariant.cc
@@ -1815,9 +1815,21 @@ Variant::to_string () const
     } else if (m_type == t_id)  {
       r = "[id" + tl::to_string (m_var.m_id) + "]";
     } else if (m_type == t_user) {
-      r = m_var.mp_user.cls->to_string (m_var.mp_user.object);
+      void *obj = m_var.mp_user.object;
+      if (obj) {
+        r = m_var.mp_user.cls->to_string (obj);
+      } else {
+        r = "[class ";
+        r += m_var.mp_user.cls->name ();
+        r += "]";
+      }
     } else if (m_type == t_user_ref) {
-      r = m_var.mp_user_ref.cls->to_string (m_var.mp_user_ref.cls->deref_proxy_const (reinterpret_cast <const tl::WeakOrSharedPtr *> (m_var.mp_user_ref.ptr)->get ()));
+      const void *obj = m_var.mp_user_ref.cls->deref_proxy_const (reinterpret_cast <const tl::WeakOrSharedPtr *> (m_var.mp_user_ref.ptr)->get ());
+      if (obj) {
+        r = m_var.mp_user_ref.cls->to_string (obj);
+      } else {
+        r = "[null]";
+      }
     } else {
       r = "[unknown]";
     }