[ntuple] Bad state after attempting to make field for virtual type

[nsmith-]

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Description

If a code attempts to create a field in an RNTuple for a virtual object type, it rightfully fails, but not with a very clear warning as to why (as compared to constructing the object on the interpreter). However, after the failure, types that should be OK to make fields from now fail. So I guess some internal data structure gets corrupted.

Reproducer

import ROOT

ROOT.gInterpreter.Declare("""\
class Abstract {
  public:
    Abstract() : data1_(3) {};
    virtual ~Abstract() {};

    virtual int method() = 0;

  private:
    int data1_;
};

class Derived : public Abstract {
  public:
    Derived() : Abstract() {};

    int method() override { return data2_; };

  private:
    int data2_;
};
""")

model = ROOT.Experimental.RNTupleModel.Create()

# Derived can be constructed without complaint
# obj1 = model.MakeField["Derived"]("test1")

# If we attempt (foolishly) to make Abstract, and
# catch the exception, then later attempts to make Derived now fail
# with puzzling JIT errors
try:
    obj1 = model.MakeField["Abstract"]("test1")
except ValueError as ex:
    print(ex)
obj2 = model.MakeField["Derived"]("test2")

ROOT version

master (6.31.01+)

Installation method

CMSSW IB (/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02807/el8_amd64_gcc12/cms/cmssw/CMSSW_13_3_ROOT6_X_2023-10-18-2300)

Operating system

EL8

Additional context

No response

[nsmith-]

The same symptom also appears if I try to make a field for a class with no default constructor:

import ROOT

ROOT.gInterpreter.Declare("""\
class NoDefaultCtor {
  public:
    NoDefaultCtor(int x) : data1_(x) {};

  private:
    int data1_;
};
""")

model = ROOT.Experimental.RNTupleModel.Create()

try:
    model.MakeField["NoDefaultCtor"]("test")
except ValueError as ex:
    print(ex)

# fails
model.MakeField["std::vector<float>"]("test2")

There, I even get

cling JIT session error: Failed to materialize symbols: { (main, { _ZSt7forwardIRPN4ROOT12Experimental6Detail10RFieldBaseEEOT_RNSt16remove_referenceIS6_E4typeE }) }

which is very weird, why would we be making the symbol

ROOT::Experimental::Detail::RFieldBase*& std::forward<ROOT::Experimental::Detail::RFieldBase*&>(std::remove_reference<ROOT::Experimental::Detail::RFieldBase*&>::type&)

[hahnjo]

After a quick look, this appears to a be a DeclUnloader problem because of the failed transaction. On the C++ prompt, both cases (abstract class and class without default constructor) work, only some warnings (again related to DeclUnloader)...