From 31cc8f32e2a50f996595ad7903f21a0636f6a3ad Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@koefferlein.de>
Date: Sun, 2 May 2021 23:00:38 +0200
Subject: [PATCH] Fixed #787 - the results of const reference return values
 need to be copied as the holder object may go out of scope

---
 src/db/unit_tests/dbLayoutQueryTests.cc | 21 +++++++++++++++++++++
 src/gsi/gsi/gsiExpression.cc            |  7 +++++++
 src/tl/unit_tests/tlExpressionTests.cc  | 21 +++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/src/db/unit_tests/dbLayoutQueryTests.cc b/src/db/unit_tests/dbLayoutQueryTests.cc
index 98ed65049..a944bd61b 100644
--- a/src/db/unit_tests/dbLayoutQueryTests.cc
+++ b/src/db/unit_tests/dbLayoutQueryTests.cc
@@ -1488,3 +1488,24 @@ TEST(63)
 
   EXPECT_EQ (g.under_construction (), false);
 }
+
+//  issue-787
+TEST(64)
+{
+  db::Layout g;
+  init_layout (g);
+
+  {
+    db::LayoutQuery q ("select inst.dtrans from instances of .*.*");
+    db::LayoutQueryIterator iq (q, &g);
+    std::string s = q2s_var (iq, "data");
+    EXPECT_EQ (s, "r0 0.01,-0.02,m45 -0.01,0.02,m45 -0.01,0.02,m45 -0.01,0.02,r0 0.01,-0.02,m45 -0.01,0.02");
+  }
+
+  {
+    db::LayoutQuery q ("select inst.dtrans.disp.x,inst.dtrans.disp.y from instances of .*.*");
+    db::LayoutQueryIterator iq (q, &g);
+    std::string s = q2s_var (iq, "data");
+    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");
+  }
+}
diff --git a/src/gsi/gsi/gsiExpression.cc b/src/gsi/gsi/gsiExpression.cc
index 4bf00218f..1836f5899 100644
--- a/src/gsi/gsi/gsiExpression.cc
+++ b/src/gsi/gsi/gsiExpression.cc
@@ -901,6 +901,13 @@ struct reader<ObjectType>
 
       tl_assert (cls != 0);
       *out = tl::Variant ();
+
+      //  consider prefer_copy
+      if (! owner && atype.prefer_copy () && !clsact->is_managed () && clsact->can_copy ()) {
+        obj = clsact->clone (obj);
+        owner = true;
+      }
+
       out->set_user (obj, cls, owner);
 
     }
diff --git a/src/tl/unit_tests/tlExpressionTests.cc b/src/tl/unit_tests/tlExpressionTests.cc
index 6c361fb6d..619b5a351 100644
--- a/src/tl/unit_tests/tlExpressionTests.cc
+++ b/src/tl/unit_tests/tlExpressionTests.cc
@@ -1189,3 +1189,24 @@ TEST(19)
   v = e.parse ("# A comment\nvar i=CellInstArray.new(17,tr,a,b,100,200); i.to_s(); # A final comment").execute ();
   EXPECT_EQ (v.to_string (), std::string ("#17 r90 10,20 [1,2*100;11,22*200]"));
 }
+
+// issue-787
+TEST(20)
+{
+  tl::Eval e;
+  e.parse ("var ly=Layout.new(true)").execute ();
+  e.parse ("var top=ly.create_cell('TOP')").execute ();
+  e.parse ("var cell=ly.create_cell('CHILD')").execute ();
+  e.parse ("var i1 = top.insert(CellInstArray.new(cell.cell_index,Trans.new(Vector.new(100,200))))").execute ();
+  e.parse ("var i2 = top.insert(CellInstArray.new(cell.cell_index,Trans.new(Vector.new(-100,300))))").execute ();
+
+  tl::Variant v;
+  v = e.parse ("i1.dtrans.disp.x").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("0.1"));
+  v = e.parse ("i1.dtrans.disp.y").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("0.2"));
+  v = e.parse ("i2.dtrans.disp.x").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("-0.1"));
+  v = e.parse ("i2.dtrans.disp.y").execute ();
+  EXPECT_EQ (v.to_string (), std::string ("0.3"));
+}