From a0758aa493fe1718607fa220c7019228957c2abb Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@klayout.de>
Date: Wed, 14 Aug 2024 06:54:43 +0200
Subject: [PATCH] WIP

---
 src/tl/tl/tlExpression.cc | 25 +++++++++++++++++++++++--
 src/tl/tl/tlExpression.h  | 12 ++++++++++--
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/tl/tl/tlExpression.cc b/src/tl/tl/tlExpression.cc
index 9da470c35..6853a5729 100644
--- a/src/tl/tl/tlExpression.cc
+++ b/src/tl/tl/tlExpression.cc
@@ -3156,6 +3156,10 @@ Expression::execute () const
 void
 Expression::execute (EvalTarget &v) const
 {
+  if (! mp_eval.get ()) {
+    throw tl::Exception (tl::to_string (tr ("Context was destroyed")));
+  }
+  mp_eval->check ();
   if (m_root.get ()) {
     m_root->execute (v);
   } 
@@ -3167,13 +3171,13 @@ Expression::execute (EvalTarget &v) const
 Eval Eval::m_global (0, 0, false);
 
 Eval::Eval (Eval *parent, bool sloppy)
-  : mp_parent (parent), mp_global (&Eval::m_global), m_sloppy (sloppy), mp_ctx_handler (0)
+  : mp_parent (parent), m_has_parent (parent != 0), mp_global (&Eval::m_global), m_has_global (false), m_sloppy (sloppy), mp_ctx_handler (0)
 {
   // .. nothing yet ..
 }
 
 Eval::Eval (Eval *global, Eval *parent, bool sloppy)
-  : mp_parent (parent), mp_global (global), m_sloppy (sloppy), mp_ctx_handler (0)
+  : mp_parent (parent), m_has_parent (parent != 0), mp_global (global), m_has_global (global != 0), m_sloppy (sloppy), mp_ctx_handler (0)
 {
   // .. nothing yet ..
 }
@@ -3186,6 +3190,23 @@ Eval::~Eval ()
   m_local_functions.clear ();
 }
 
+void
+Eval::check ()
+{
+  if (m_has_parent) {
+    if (! mp_parent.get ()) {
+      throw tl::Exception (tl::to_string (tr ("Parent context was destroyed")));
+    }
+    mp_parent->check ();
+  }
+  if (m_has_global) {
+    if (! mp_global.get ()) {
+      throw tl::Exception (tl::to_string (tr ("Global context was destroyed")));
+    }
+    mp_global->check ();
+  }
+}
+
 void 
 Eval::set_var (const std::string &name, const tl::Variant &var)
 {
diff --git a/src/tl/tl/tlExpression.h b/src/tl/tl/tlExpression.h
index b1a6d5f6a..ffef940e9 100644
--- a/src/tl/tl/tlExpression.h
+++ b/src/tl/tl/tlExpression.h
@@ -356,7 +356,7 @@ private:
   const char *mp_text;
   std::string m_local_text;
   std::unique_ptr<ExpressionNode> m_root;
-  Eval *mp_eval;
+  tl::weak_ptr<Eval> mp_eval;
 
   friend class Eval;
 
@@ -580,10 +580,18 @@ public:
     return mp_parent.get ();
   }
 
+  /**
+   *  @brief Checks the contexts and throws an exception if one of them got lost
+   */
+  void check ();
+
 private:
   friend class Expression;
 
-  tl::weak_ptr<Eval> mp_parent, mp_global;
+  tl::weak_ptr<Eval> mp_parent;
+  bool m_has_parent;
+  tl::weak_ptr<Eval> mp_global;
+  bool m_has_global;
   std::map <std::string, tl::Variant> m_local_vars;
   std::map <std::string, EvalFunction *> m_local_functions;
   bool m_sloppy;