Automatic Template Instantiation In DIGITAL C++

Automatic template instantiation in DIGITAL C++ version 6.0 employs a compile-time scheme that generates instantiation object files into a repository. This paper provides an overview of the C++ template facility and the template instantiation process, including manual and automatic instantiation techniques. It reviews the features of template instantiation in DIGITAL C++ and focuses on the development and implementation of automatic template instantiation in DIGITAL C++ version 6.0. The template facility within the C++ language allows the user to provide a template for a class or function and then apply specific arguments to the template to specify a type or function. The process of applying arguments to a template, referred to as template instantiation, causes specific code to be generated to implement the functions and static data members of the instantiated template as needed by the program. Automatic template instantiation relieves the user of determining which template entities need to be instantiated and where they should be instantiated. In this paper, we review the C++ template facility and describe approaches to implementing automatic template instantiation. We follow that with a discussion of the facilities, rationale, and experience of the DIGITAL C++ automatic template instantiation support. We then describe the design of the DIGITAL C++ version 6.0 automatic template instantiation facility and indicate areas to be explored for further improvement. C++ Template Facility The C++ language provides a template facility that allows the user to create a family of classes or functions that are parameterized by type. 1,2 For example, a user may provide a Stack template, which defines a stack class for its argument type. Consider the following template declaration: template <class T> class Stack { T *top_of_stack; public: void push ( T arg); void pop ( T & arg); The act of applying the arguments to the template is referred to as template instantiation. An instantiation of a template creates a new type or function that is defined for the specified types. Stack<int> creates a class that provides a stack of the type int. Stack<user_class> creates a class that provides a stack of user_class. The types int and user_class are the arguments for the template Stack