From 332e015889d414482ff35bb254a6881c05f1d6bc Mon Sep 17 00:00:00 2001
From: Christian Tacke <58549698+ChristianTackeGSI@users.noreply.github.com>
Date: Mon, 22 Apr 2024 09:14:47 +0200
Subject: [PATCH] fix: Properly clean up TList in FairGeoSet

FairGeoSet has non-owning references inside a TList to
FairGeoNodes.  When the dtor of FairGeoSet is called, those
FairGeoNodes might already have been destroyed.

Calling `Clear` with `"nodelete"` will just remove all the
references without touching them.
---
 fairroot/geobase/FairGeoSet.cxx | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fairroot/geobase/FairGeoSet.cxx b/fairroot/geobase/FairGeoSet.cxx
index d1045c4257..02296e0a7a 100644
--- a/fairroot/geobase/FairGeoSet.cxx
+++ b/fairroot/geobase/FairGeoSet.cxx
@@ -41,6 +41,12 @@ using std::ios;
 FairGeoSet::~FairGeoSet()
 {
     // Destructor
+    if (volumes && !volumes->IsOwner()) {
+        // destructing a TList that doesn't own its contents
+        // still touches the objects inside, even if they're
+        // already destroeyed
+        volumes->Clear("nodelete");
+    }
     delete volumes;
     volumes = 0;
     delete modules;