From 3a29d356cb651322e1ab2c99785d00ef7aad2fdb Mon Sep 17 00:00:00 2001
From: Stephan Hageboeck <stephan.hageboeck@cern.ch>
Date: Fri, 20 Mar 2026 11:16:17 +0100
Subject: [PATCH] [tmva] Retire TH1::AddDirectory use in TMVA.

Replace uses of TH1::AddDirectory by TDirectory::TContext. It is
thread-local and uses the RAII idiom, so state changes cannot
inadvertently leak out of TMVA functions.
---
 tmva/tmva/src/MethodBase.cxx             |  5 +----
 tmva/tmva/src/MethodLikelihood.cxx       | 12 +++---------
 tmva/tmva/src/PDEFoam.cxx                |  5 +----
 tmva/tmva/src/VariableGaussTransform.cxx |  4 +---
 4 files changed, 6 insertions(+), 20 deletions(-)

diff --git a/tmva/tmva/src/MethodBase.cxx b/tmva/tmva/src/MethodBase.cxx
index 32ca641140c54..608194a490557 100644
--- a/tmva/tmva/src/MethodBase.cxx
+++ b/tmva/tmva/src/MethodBase.cxx
@@ -1458,13 +1458,10 @@ void TMVA::MethodBase::WriteStateToXML( void* parent ) const
 
 void TMVA::MethodBase::ReadStateFromStream( TFile& rf )
 {
-   Bool_t addDirStatus = TH1::AddDirectoryStatus();
-   TH1::AddDirectory( 0 ); // this avoids the binding of the hists in PDF to the current ROOT file
+   TDirectory::TContext dirCtx{nullptr}; // Don't register histograms to current directory
    fMVAPdfS = (TMVA::PDF*)rf.Get( "MVA_PDF_Signal" );
    fMVAPdfB = (TMVA::PDF*)rf.Get( "MVA_PDF_Background" );
 
-   TH1::AddDirectory( addDirStatus );
-
    ReadWeightsFromStream( rf );
 
    SetTestvarName();
diff --git a/tmva/tmva/src/MethodLikelihood.cxx b/tmva/tmva/src/MethodLikelihood.cxx
index 5c715c9571c86..f7033a6eb7e13 100644
--- a/tmva/tmva/src/MethodLikelihood.cxx
+++ b/tmva/tmva/src/MethodLikelihood.cxx
@@ -668,8 +668,7 @@ void  TMVA::MethodLikelihood::WriteWeightsToStream( TFile& ) const
 void  TMVA::MethodLikelihood::ReadWeightsFromXML(void* wghtnode)
 {
    TString pname = "PDF_";
-   Bool_t addDirStatus = TH1::AddDirectoryStatus();
-   TH1::AddDirectory(0); // this avoids the binding of the hists in TMVA::PDF to the current ROOT file
+   TDirectory::TContext dirCtx{nullptr}; // Don't register histograms to current directory
    UInt_t nvars=0;
    gTools().ReadAttr(wghtnode, "NVariables",nvars);
    void* descnode = gTools().GetChild(wghtnode);
@@ -688,7 +687,6 @@ void  TMVA::MethodLikelihood::ReadWeightsFromXML(void* wghtnode)
       (*(*fPDFBgd)[ivar]).ReadXML(pdfnode);
       descnode = gTools().GetNextChild(descnode);
    }
-   TH1::AddDirectory(addDirStatus);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -698,8 +696,7 @@ void  TMVA::MethodLikelihood::ReadWeightsFromXML(void* wghtnode)
 void  TMVA::MethodLikelihood::ReadWeightsFromStream( std::istream & istr )
 {
    TString pname = "PDF_";
-   Bool_t addDirStatus = TH1::AddDirectoryStatus();
-   TH1::AddDirectory(0); // this avoids the binding of the hists in TMVA::PDF to the current ROOT file
+   TDirectory::TContext dirCtx{nullptr}; // Don't register histograms to current directory
    for (UInt_t ivar=0; ivar<GetNvar(); ivar++){
       Log() << kDEBUG << "Reading signal and background PDF for variable: " << GetInputVar( ivar ) << Endl;
       if ((*fPDFSig)[ivar] !=0) delete (*fPDFSig)[ivar];
@@ -711,7 +708,6 @@ void  TMVA::MethodLikelihood::ReadWeightsFromStream( std::istream & istr )
       istr >> *(*fPDFSig)[ivar];
       istr >> *(*fPDFBgd)[ivar];
    }
-   TH1::AddDirectory(addDirStatus);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -720,13 +716,11 @@ void  TMVA::MethodLikelihood::ReadWeightsFromStream( std::istream & istr )
 void  TMVA::MethodLikelihood::ReadWeightsFromStream( TFile& rf )
 {
    TString pname = "PDF_";
-   Bool_t addDirStatus = TH1::AddDirectoryStatus();
-   TH1::AddDirectory(0); // this avoids the binding of the hists in TMVA::PDF to the current ROOT file
+   TDirectory::TContext dirCtx{nullptr}; // Don't register histograms to current directory
    for (UInt_t ivar=0; ivar<GetNvar(); ivar++){
       (*fPDFSig)[ivar] = (TMVA::PDF*)rf.Get( TString::Format( "PDF_%s_S", GetInputVar( ivar ).Data() ) );
       (*fPDFBgd)[ivar] = (TMVA::PDF*)rf.Get( TString::Format( "PDF_%s_B", GetInputVar( ivar ).Data() ) );
    }
-   TH1::AddDirectory(addDirStatus);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/tmva/tmva/src/PDEFoam.cxx b/tmva/tmva/src/PDEFoam.cxx
index b61f387e27571..3825d1d3e3124 100644
--- a/tmva/tmva/src/PDEFoam.cxx
+++ b/tmva/tmva/src/PDEFoam.cxx
@@ -288,8 +288,7 @@ void TMVA::PDEFoam::SetXmax(Int_t idim, Double_t wmax)
 
 void TMVA::PDEFoam::Create()
 {
-   Bool_t addStatus = TH1::AddDirectoryStatus();
-   TH1::AddDirectory(kFALSE);
+   TDirectory::TContext dirCtx{nullptr}; // Don't register histograms to current directory
 
    if(fPseRan==0) Log() << kFATAL << "Random number generator not set" << Endl;
    if(fDistr==0)  Log() << kFATAL << "Distribution function not set" << Endl;
@@ -340,8 +339,6 @@ void TMVA::PDEFoam::Create()
    InitCells();
    Grow();
 
-   TH1::AddDirectory(addStatus);
-
    // prepare PDEFoam for the filling with events
    ResetCellElements(); // reset all cell elements
 } // Create
diff --git a/tmva/tmva/src/VariableGaussTransform.cxx b/tmva/tmva/src/VariableGaussTransform.cxx
index f3e447d2be802..777278d70b9f1 100644
--- a/tmva/tmva/src/VariableGaussTransform.cxx
+++ b/tmva/tmva/src/VariableGaussTransform.cxx
@@ -549,8 +549,7 @@ void TMVA::VariableGaussTransform::ReadFromXML( void* trfnode ) {
 
 void TMVA::VariableGaussTransform::ReadTransformationFromStream( std::istream& istr, const TString& classname)
 {
-   Bool_t addDirStatus = TH1::AddDirectoryStatus();
-   TH1::AddDirectory(0); // this avoids the binding of the hists in TMVA::PDF to the current ROOT file
+   TDirectory::TContext dirCtx{nullptr}; // Don't register histograms to current directory
    char buf[512];
    istr.getline(buf,512);
 
@@ -615,7 +614,6 @@ void TMVA::VariableGaussTransform::ReadTransformationFromStream( std::istream& i
 
       istr.getline(buf,512); // reading the next line
    }
-   TH1::AddDirectory(addDirStatus);
 
    UInt_t classIdx=(classname=="signal")?0:1;
    for(UInt_t ivar=0; ivar<fCumulativePDF.size(); ++ivar) {