but routines can call other routines, without first returning to MAIN, true?

MAIN
  &routineA

ROUTINEA
  &routineB

ROUTINEB
  .....
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so a flow that works is :

MAIN
  new C++object
  routineA(C++object)
  routineB(C++object)
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but a flow that does NOT work is :

MAIN
  my C++object = routineA
  C++object->method
ROUTINEA
  my C++object = new C++design
  return C++object
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yes, i agree with your last statement. ( that it is a C++ usage/style issue ) although we use SWIG, instead of XS.