From 767adeba3cc9738914163e9282299a369bd3043b Mon Sep 17 00:00:00 2001
From: jmcarcell <jmcarcell@users.noreply.github.com>
Date: Tue, 17 Dec 2024 10:13:56 +0100
Subject: [PATCH] Fix the issue where the vector being iterated over is
 modified in the loop

---
 k4FWCore/components/Writer.cpp | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/k4FWCore/components/Writer.cpp b/k4FWCore/components/Writer.cpp
index 7ee461c6..851ea404 100644
--- a/k4FWCore/components/Writer.cpp
+++ b/k4FWCore/components/Writer.cpp
@@ -19,6 +19,7 @@
 
 #include "Gaudi/Functional/Consumer.h"
 #include "GaudiKernel/AnyDataWrapper.h"
+#include "GaudiKernel/DataObject.h"
 #include "GaudiKernel/IDataManagerSvc.h"
 #include "GaudiKernel/IDataProviderSvc.h"
 #include "GaudiKernel/IHiveWhiteBoard.h"
@@ -133,8 +134,8 @@ class Writer final : public Gaudi::Functional::Consumer<void(const EventContext&
   }
 
   void getOutputCollections() const {
-    SmartIF<IDataManagerSvc> m_mgr;
-    m_mgr = eventSvc();
+    SmartIF<IDataManagerSvc> mgr;
+    mgr = eventSvc();
 
     SmartDataPtr<DataObject> root(eventSvc(), "/Event");
     if (!root) {
@@ -147,13 +148,8 @@ class Writer final : public Gaudi::Functional::Consumer<void(const EventContext&
       error() << "Failed to retrieve the root registry object" << endmsg;
       return;
     }
-    auto mgr = eventSvc().as<IDataManagerSvc>();
-    if (!mgr) {
-      error() << "Failed to retrieve IDataManagerSvc" << endmsg;
-      return;
-    }
     std::vector<IRegistry*> leaves;
-    StatusCode              sc = m_mgr->objectLeaves(pObj, leaves);
+    StatusCode              sc = mgr->objectLeaves(pObj, leaves);
     if (!sc.isSuccess()) {
       error() << "Failed to retrieve object leaves" << endmsg;
       return;
@@ -240,6 +236,7 @@ class Writer final : public Gaudi::Functional::Consumer<void(const EventContext&
       delete storePtr;
     }
 
+    std::vector<std::string_view> collectionsToRemove;
     for (const auto& coll : m_collectionsToAdd) {
       DataObject* storeCollection;
       if (m_dataSvc->retrieveObject("/Event/" + coll, storeCollection).isFailure()) {
@@ -264,10 +261,11 @@ class Writer final : public Gaudi::Functional::Consumer<void(const EventContext&
           // anything else
           info() << "Object in the store with name " << coll
                  << " does not look like a collection so it can not be written to the output file" << endmsg;
+          // Collections to remove in m_collectionsToAdd are saved for later
+          // not to modify the vector while iterating over it
+          collectionsToRemove.push_back(coll);
           m_collectionsToSave.erase(std::remove(m_collectionsToSave.begin(), m_collectionsToSave.end(), coll),
                                     m_collectionsToSave.end());
-          m_collectionsToAdd.erase(std::remove(m_collectionsToAdd.begin(), m_collectionsToAdd.end(), coll),
-                                   m_collectionsToAdd.end());
         } else {
           std::unique_ptr<podio::CollectionBase> uptr(
               const_cast<podio::CollectionBase*>(old_collection->collectionBase()));
@@ -276,6 +274,11 @@ class Writer final : public Gaudi::Functional::Consumer<void(const EventContext&
       }
     }
 
+    for (const auto& coll : collectionsToRemove) {
+      m_collectionsToAdd.erase(std::remove(m_collectionsToAdd.begin(), m_collectionsToAdd.end(), coll),
+                               m_collectionsToAdd.end());
+    }
+
     debug() << "Writing frame" << endmsg;
     iosvc->getWriter().writeFrame(ptr->getData(), podio::Category::Event, m_collectionsToSave);
   }