In PODIO 00-16-05, ROOTLegacyReader can't read files written by 00-16-02

[veprbl]

• OS version: macOS or ePIC container on linux
• Compiler version: varies
• PODIO version: 00-16-05
• Reproduced by: try reading old_sim
• Input: old_sim.edm4hep.root.gz, new_sim.edm4hep.root.gz
• Output:
• Goal: read files produced with older software

We are seeing issues with reading files produced with an older version of PODIO using a newer version of PODIO. Files produced with a newer version can be read just fine with the older.

Strangely, we see some unknown-origin std::exception with no useful .what(). However, with some massaging, it can also segfault. The exception/segfault happens on a very first readEntry.

Thread model: pthreads
0x700004265000: 
       `- JSignalHandler::handle_sigsegv(int, __siginfo*, void*) (0x10577d7fc)
        `- _sigtramp (0x7fff20612d7d)
         `- 4   ???                                 0x0000000000000000 0x0 + 0 (0x0)
          `- podio::ROOTLegacyReader::getCollectionBuffers(std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::tuple<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, bool, unsigned int, unsigned long> > const&) (0x106f593e8)
           `- podio::ROOTLegacyReader::readEntry() (0x106f58d8d)
            `- podio::ROOTLegacyReader::readEntry(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned int) (0x106f59375)
             `- JEventSourcePODIOLegacy::GetEvent(std::__1::shared_ptr<JEvent>) (0x109fa8f14)
              `- JEventSource::DoNext(std::__1::shared_ptr<JEvent>) (0x105724ccf)
               `- JEventSourceArrow::execute(JArrowMetrics&, unsigned long) (0x105729f2b)
                `- JWorker::loop() (0x10572db5c)
                 `- void* std::__1::__thread_proxy<std::__1::tuple<std::__1::unique_ptr<std::__1::__thread_struct, std::__1::default_delete<std::__1::__thread_struct> >, void (JWorker::*)(), JWorker*> >(void*) (0x10572ed7e)
                  `- _pthread_start (0x7fff205cd8fc)
                   `- thread_start (0x7fff205c9443)

[veprbl]

Thank you