Merge branch 'MG_MemLeaks_VertexIterativeMergingTool' into 'main'

[ATLASDPD-2027] fix memleak in VertexIterativeFitMergingTool

See merge request !69573

PhysicsAnalysis/AnalysisCommon/LeptonTaggers/LeptonTaggers/VertexIterativeFitMergingTool.h

 // This is -*- c++ -*-
 
 /*
-  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef PROMPT_VERTEXITERATIVEFITMERGINGTOOL_H
@@ -149,6 +149,17 @@ namespace Prompt
       const VtxType vtxType,
       std::vector<TwoTrackVtx> &others
     );
+    /*
+      Second signature for the iterative vertex fit. 
+      This one assumes the seed is owned by the caller. 
+      Used to prevent memory leaks within the recursion step 
+    */
+    xAOD::Vertex* fitSeedVertexCluster(
+      const FittingInput &input,
+      std::unique_ptr<xAOD::Vertex> & seedVtx,
+      const VtxType vtxType,
+      std::vector<TwoTrackVtx> &others
+    );
 
     std::unique_ptr<xAOD::Vertex> fitSeedPlusOtherVertex(
       const FittingInput &input,

PhysicsAnalysis/AnalysisCommon/LeptonTaggers/src/VertexIterativeFitMergingTool.cxx

@@ -459,14 +459,10 @@ xAOD::Vertex* Prompt::VertexIterativeFitMergingTool::fitSeedVertexCluster(
 
   /*
     Found nearby vertex - fit merged vertex
-
-    We release the unique_ptr here because we don't want
-    to deal with ownership semantics in the recursive function.
-    The caller will re-capture the vertex in a unique_ptr.
   */
-  xAOD::Vertex* candVtx = fitSeedPlusOtherVertex(
+  std::unique_ptr<xAOD::Vertex> candVtx =fitSeedPlusOtherVertex(
     input, seedVtx, currVtx, vtxType
-  ).release();
+  ); 
 
   if(!candVtx) {
     //
@@ -479,7 +475,7 @@ xAOD::Vertex* Prompt::VertexIterativeFitMergingTool::fitSeedVertexCluster(
     return fitSeedVertexCluster(input, std::move(seedVtx), vtxType, others);
   }
 
-  const double probCand = getVertexFitProb(candVtx);
+  const double probCand = getVertexFitProb(candVtx.get());
   const double probSeed = getVertexFitProb(seedVtx);
 
   double probCandOverSeed = -1.0;
@@ -488,8 +484,8 @@ xAOD::Vertex* Prompt::VertexIterativeFitMergingTool::fitSeedVertexCluster(
     probCandOverSeed = probCand/probSeed;
   }
 
-  const double distToSeed = getDistance(seedVtx, candVtx);
-  const double distToCurr = getDistance(currVtx, candVtx);
+  const double distToSeed = getDistance(seedVtx, candVtx.get());
+  const double distToCurr = getDistance(currVtx, candVtx.get());
 
   fillTH1(m_histNewVtxFitChi2, candVtx->chiSquared());
   fillTH1(m_histNewVtxFitProb, probCand);
@@ -508,13 +504,13 @@ xAOD::Vertex* Prompt::VertexIterativeFitMergingTool::fitSeedVertexCluster(
     str << "   dist to seed=" << distToSeed << ", probCandOverSeed=" << probCandOverSeed << std::endl
   << "   seed: "        << vtxAsStr(seedVtx, false) << std::endl
   << "   curr: "        << vtxAsStr(currVtx, true)
-  << "   cand: "        << vtxAsStr(candVtx, true)
+  << "   cand: "        << vtxAsStr(candVtx.get(), true)
   << "fitSeedVertexCluster - finished" << std::endl
   << "---------------------------------------------------------------------------" << std::endl;
 
 
 
-  if(!(passVertexSelection(candVtx) && probCandOverSeed > m_minCandOverSeedFitProbRatio)) {
+  if(!(passVertexSelection(candVtx.get()) && probCandOverSeed > m_minCandOverSeedFitProbRatio)) {
     //
     // New fitted merged vertex failed selection
     //
@@ -548,6 +544,27 @@ xAOD::Vertex* Prompt::VertexIterativeFitMergingTool::fitSeedVertexCluster(
   return fitSeedVertexCluster(input, candVtx, vtxType, others);
 }
 
+// this signature is only called recursively, if a merged vertex candidate has been
+// found.  Ensures that we release the final merged candidate to hand it 
+// back to the original caller. 
+xAOD::Vertex* Prompt::VertexIterativeFitMergingTool::fitSeedVertexCluster(
+  const FittingInput &input,
+      std::unique_ptr<xAOD::Vertex> & seedVtx,
+  const VtxType vtxType,
+  std::vector<TwoTrackVtx> &others
+){
+  // remember the seed vertex before the call 
+  xAOD::Vertex* originalSeed = seedVtx.get(); 
+  // call the original signature 
+  xAOD::Vertex* iterationResult = fitSeedVertexCluster(input,seedVtx.get(), vtxType,others); 
+  // if the iteration has finished (it is returning the seed), release the seed vertex. 
+  // This will be re-captured by the top level caller after exiting the recursion stack.
+  if (iterationResult == originalSeed) return seedVtx.release();
+  // otherwise, return the iteration result. The seed vertex will be deleted 
+  // when the call stack unwinds.  
+  else return iterationResult; 
+}
+
 unsigned Prompt::VertexIterativeFitMergingTool::removeMerged2TrackVertexes(
   const xAOD::Vertex *mergedVtx,
   std::vector<TwoTrackVtx> &vtxs