From 850a6f56d3703c39ed9057e4ca4f914f4996f1ed Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@klayout.de>
Date: Tue, 25 Feb 2025 23:22:06 +0100
Subject: [PATCH] [consider merging] avoid a crash during certain queries

This query used to crash:
"instances of cell .*.* where inst.trans.rot == 2"
on a layout with 1 hierarchy level and some cells with rot 180 degree
---
 src/db/db/dbLayoutQuery.cc              | 14 +++++++++-----
 src/db/unit_tests/dbLayoutQueryTests.cc | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/db/db/dbLayoutQuery.cc b/src/db/db/dbLayoutQuery.cc
index d2753b617..c5989b5bb 100644
--- a/src/db/db/dbLayoutQuery.cc
+++ b/src/db/db/dbLayoutQuery.cc
@@ -1006,15 +1006,19 @@ public:
 
       db::Instance inst;
       if (m_reading) {
-        inst = mp_parent->sorted_inst_ptr (std::distance (mp_parent->begin_sorted_insts (), m_inst));
+        if (mp_parent) {
+          inst = mp_parent->sorted_inst_ptr (std::distance (mp_parent->begin_sorted_insts (), m_inst));
+        }
       } else {
         inst = m_i;
       }
 
-      if (m_instance_mode == ArrayInstances) {
-        v.push (tl::Variant (db::InstElement (inst)));
-      } else {
-        v.push (tl::Variant (db::InstElement (inst, m_array_iter)));
+      if (! inst.is_null ()) {
+        if (m_instance_mode == ArrayInstances) {
+          v.push (tl::Variant (db::InstElement (inst)));
+        } else {
+          v.push (tl::Variant (db::InstElement (inst, m_array_iter)));
+        }
       }
       return true;
 
diff --git a/src/db/unit_tests/dbLayoutQueryTests.cc b/src/db/unit_tests/dbLayoutQueryTests.cc
index e93171e89..77f091cd2 100644
--- a/src/db/unit_tests/dbLayoutQueryTests.cc
+++ b/src/db/unit_tests/dbLayoutQueryTests.cc
@@ -1578,3 +1578,20 @@ TEST(64)
     EXPECT_EQ (s, "(0.01,-0.02),(-0.01,0.02),(-0.01,0.02),(-0.01,0.02),(0.01,-0.02),(-0.01,0.02)");
   }
 }
+
+TEST(65)
+{
+  db::Layout g;
+  init_layout (g);
+
+  {
+    db::LayoutQuery q ("instances of cell .*.* where inst.trans.rot == 0");
+    db::LayoutQueryIterator iq (q, &g);
+    std::string s = q2s_var (iq, "data");
+    EXPECT_EQ (s, "nil,nil");
+    s = q2s_var (iq, "cell_name");
+    EXPECT_EQ (s, "c1,c5x");
+    s = q2s_var (iq, "inst_elements");
+    EXPECT_EQ (s, "(cell_index=0 r0 *1 10,-20),(cell_index=4 r0 *1 10,-20)");
+  }
+}