Generate dictionary for dinamically created custom STL collections

ROOT
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2

Hi @mroguljic ,

TL;DR:
I cannot reproduce the issue, I think we will need a minimal self-contained reproducer for your problem.

Given the following files:

// myclass.h
#ifndef MYCLASS
#define MYCLASS
struct MyClass { int data = -1; };
#endif

// foo.cpp
#include "myclass.h"
#include <ROOT/RDataFrame.hxx>
#include <TInterpreter.h>
#include <vector>

int main() {
  gInterpreter->GenerateDictionary("MyClass;std::vector<MyClass>", "myclass.h");

  {
    ROOT::RDataFrame(10)
        .Define("c",
                [](ULong64_t e) {
                  return std::vector<MyClass>{{int(e)}, {int(e)}};
                },
                {"rdfentry_"})
        .Snapshot<std::vector<MyClass>>("t", "f.root", {"c"});

    TFile f("f.root");
    auto *t = f.Get<TTree>("t");
    t->Scan();
  }

  // with jitting
  {
    ROOT::RDataFrame(10)
        .Define("c", [](ULong64_t e) { return std::vector<MyClass>{{int(e)}}; },
                {"rdfentry_"})
        .Snapshot<std::vector<MyClass>>("t", "f.root", {"c"});

    TFile f("f.root");
    auto *t = f.Get<TTree>("t");
    t->Scan();
  }
}

The following invocation works and produces the expected output both with ROOT master and with v6.24 installed via conda:

g++ -g -Wall -Wextra -Wpedantic -o "foo" "foo.cpp" $(root-config --cflags --libs) && ./foo

What am I doing differently?

Cheers,
Enrico