cint and multiple inheritance

From: Paolo Calafiura (PCalafiura@lbl.gov)
Date: Fri Oct 09 1998 - 21:37:04 MEST 

Hi Rooters,
 I am helping to interface root to a calibration module in order to
monitor and to analyze constants while they are taken.
The constants of each subdetector are structured in memory as STL
vectors of channels, which are very simple classes like:
    vector<channel*> cs(2000);

class channel {
public:
  channel() {};
   ... usual stuff ...
  
private:
  float _slope;
  float _error;
}

I would like to be able to "decorate" channel with TObject functionality
to make it browsable, streamable etc, but I don't want to have channel
to inherit directly from TObject (BTW I don't think this would help
because, I understand, cint does not like STL vectors).

So I decided to make a memory copy of my vector into a TClonesArray of a
TObject-derived RChannel. The point is that, as I have many kinds of
"channel" classes, I don't want to re-write by hand each "RChannel"
class with all of its member data and functions. It seemed to me a
perfect case to use multiple inheritance:

    TClonesArray *tcs = new TClonesArray("RChannel", cs.size());

class RChannel : public channel, public TObject {
public:
  RChannel(){}
  RChannel(const RChannel &c):channel(c),TObject(c) {}
  RChannel(const channel &c):channel(c),TObject() {}
  ClassDef(RChannel,1)
};

and this indeed works fine as long as I access channel data in RChannel
from my program. So, I thought, I can now write out data to a root
file...

Unfortunately the root file turns out to be empty because rootcint just
ignores the fact that RChannel is a channel and considers it as an empty
TObject! 
There is no mention to the TChannel inherited data members (slope and
error)
anywhere in the rootcint-generated TChannelCint.cc/.h. In particular

void RChannel::Streamer(TBuffer &R__b)
{
   // Stream an object of class RChannel.

   if (R__b.IsReading()) {
      Version_t R__v = R__b.ReadVersion(); if (R__v) { }
      TObject::Streamer(R__b);
   } else {
      R__b.WriteVersion(RChannel::IsA());
      TObject::Streamer(R__b);
   }
}


Is this a bug of rootcint or is it expected? And if so, can anybody
suggest me another way to "decorate" an existing data class with TObject
behaviour, short of having the existing class itself to inherit from
TObject?

Thanks and Ciao
-- 
Paolo Calafiura  
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