bugfix: correct NULL pointer protections, propagate required information about the...

diff --git a/HLT/TPCLib/AliHLTTPCConfMapFit.cxx b/HLT/TPCLib/AliHLTTPCConfMapFit.cxx
index dc4f1ac9761fc53e37ed25a13436dfb44ecd9ff2..c6a9ca8d60b987f730189aa8edff7c0d566177f7 100644 (file)
--- a/HLT/TPCLib/AliHLTTPCConfMapFit.cxx
+++ b/HLT/TPCLib/AliHLTTPCConfMapFit.cxx
@@ -486,8 +486,9 @@ Int_t AliHLTTPCConfMapFit::FitLine ( )
       // AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)hits->At(hit_counter);
       AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
       // if ( GetCurrentHit() != GetFirstHit() ) 
-      if(cHit != fTrack->GetFirstHit())//  hits->First())
+      if(previousHit)//  hits->First())
        {
+         // this means cHit != fTrack->GetFirstHit()
          dx   = cHit->GetX() - previousHit->GetX() ;
          dy   = cHit->GetY() - previousHit->GetY() ;
          dpsi = 0.5 * (Double_t)sqrt ( dx*dx + dy*dy ) / radius ;
@@ -716,13 +717,19 @@ Int_t AliHLTTPCConfMapFit::FitLineSZ ( ){
     // change Double_t s = 0.; -> slength
     Double_t slength = 0.;
 
+    // Matthias 23.02.2011
+    // this looks like a bug: previousHit is initialized, not changed
+    // in the loop, but dereferenced for all but the first hit
+    // changing the condition and adding an assignment at the end
+    // of the loop
     AliHLTTPCConfMapPoint *previousHit = NULL;
   
     // - Loop over hits calculating length in xy-plane: s
     // - Loop over hits calculating average : sav
     for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
        AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
-       if(currentHit != fTrack->GetFirstHit()) {
+       if(previousHit) {
+           // this means currentHit != fTrack->GetFirstHit()
            Double_t dx = currentHit->GetX() - previousHit->GetX() ;
            Double_t dy = currentHit->GetY() - previousHit->GetY() ;
            slength = previousHit->GetS() - (Double_t)sqrt ( dx*dx + dy*dy );
@@ -737,6 +744,10 @@ Int_t AliHLTTPCConfMapFit::FitLineSZ ( ){
 
        S   += currentHit->GetZWeight();
        Ss  += currentHit->GetZWeight() * currentHit->GetS();
+
+       // Matthias 23.02.2011
+       // adding missing assignment, otherwise previousHit stays NULL
+       previousHit=currentHit;
     }
 
     Double_t sav = (Double_t)Ss / S;