On the object-oriented design of reference-counted shadow objects

Abstract

The object-oriented programming (OOP) constructs of Fortran 2003 facilitate an elegant memory management solution of particular value when Fortran drives a second language that does not provide automatic garbage collection. More specifically, when Fortran derived types shadow a companion language's objects, safe and economical execution requires destroying the companion objects when and only when all corresponding shadows have expired. This paper focuses on the object-oriented design (OOD) of reference-counted shadow objects. The presented class structure automatically controls the lifetimes of any shadow objects that extend a universal parent class. The paper also discusses a relevant use case in ForTrilinos, a set of object-oriented Fortran interfaces to C++ packages in the Trilinos parallel numerical solver library1.