RNTupleView segfaults if used after reader destruction

[jblomer]

Check duplicate issues.

• Checked for duplicates

Description

When accessed after the generating RNTupleReader is gone, the RNTupleView segfaults. It should fail more gracefully.

Reproducer

TEST(RNTuple, ViewPastLifetime)
{
   FileRaii fileGuard("test_ntuple_view_pastlifetime.root");

   auto model = RNTupleModel::Create();
   auto fieldPt = model->MakeField<float>("pt", 42.0);
   {
      auto writer = RNTupleWriter::Recreate(std::move(model), "ntpl", fileGuard.GetPath());
      writer->Fill();
   }

   auto reader = RNTupleReader::Open("ntpl", fileGuard.GetPath());
   EXPECT_EQ(1u, reader->GetNEntries());
   auto viewPt = reader->GetView<float>("pt");
   reader.reset();
   EXPECT_FLOAT_EQ(42.0, viewPt(0));
}

ROOT version

master

Installation method

n/a

Operating system

n/a

Additional context

No response

[ferdymercury]

Reproducer without unknown FileRaii class:

#include <ROOT/RNTupleModel.hxx>
#include <ROOT/RNTupleWriter.hxx>
#include <ROOT/RNTupleReader.hxx>

using RNTupleModel = ROOT::Experimental::RNTupleModel;
using RNTupleWriter = ROOT::Experimental::RNTupleWriter;
using RNTupleReader = ROOT::Experimental::RNTupleReader;

void ntuple()
{
   auto model = RNTupleModel::Create();
   auto fieldPt = model->MakeField<float>("pt", 42.0);
   {
      auto writer = RNTupleWriter::Recreate(std::move(model), "ntpl", "test_ntuple_view_pastlifetime.root");
      writer->Fill();
   }

   auto reader = RNTupleReader::Open("ntpl", "test_ntuple_view_pastlifetime.root");
//   EXPECT_EQ(1u, reader->GetNEntries());
   auto viewPt = reader->GetView<float>("pt");
   reader.reset();
   viewPt(0);
}

I guess RNTuple should keep a shared_ptr to all GetViews created and invalidate them individually if reader.reset is called.