From 939fdebbb451240ae8988694b381f24f048d60cc Mon Sep 17 00:00:00 2001
From: Enrico Guiraud <enrico.guiraud@cern.ch>
Date: Wed, 22 Mar 2017 17:51:16 +0100
Subject: [PATCH] [TDF] Allow proper re-usage of TDataFrameValues

Before this fix TDataFrame could attempt to re-use invalidated
TTreeReader{Value,Array}s in certain conditions.
---
 tree/treeplayer/inc/ROOT/TDFNodes.hxx | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tree/treeplayer/inc/ROOT/TDFNodes.hxx b/tree/treeplayer/inc/ROOT/TDFNodes.hxx
index 6f33f8f8e4de5..d23ae7b9f85e6 100644
--- a/tree/treeplayer/inc/ROOT/TDFNodes.hxx
+++ b/tree/treeplayer/inc/ROOT/TDFNodes.hxx
@@ -137,6 +137,7 @@ public:
 
    void MakeProxy(TTreeReader &r, const std::string &bn)
    {
+      Reset();
       bool useReaderValue = std::is_same<ProxyParam_t, T>::value;
       if (useReaderValue)
          fReaderValue.reset(new TTreeReaderValue<T>(r, bn.c_str()));
@@ -163,6 +164,14 @@ public:
 
       return std::array_view<ProxyParam_t>(fReaderArray->begin(), fReaderArray->end());
    }
+
+   void Reset() {
+      fReaderValue = nullptr;
+      fReaderArray = nullptr;
+      fValuePtr = nullptr;
+      fTmpColumn = nullptr;
+      fSlot = 0;
+   }
 };
 
 template <typename T>
@@ -528,6 +537,7 @@ public:
 template <typename T>
 void ROOT::Internal::TDataFrameValue<T>::SetTmpColumn(unsigned int slot, ROOT::Detail::TDataFrameBranchBase *tmpColumn)
 {
+   Reset();
    fTmpColumn = tmpColumn;
    if (tmpColumn->GetTypeId() != typeid(T))
       throw std::runtime_error(std::string("TDataFrameValue: type specified is ") + typeid(T).name() +