HP aC++/HP C A.06.28 Programmer's Guide Integrity servers (769150-001, March 2014)

Explicit Instantiation
You request explicit instantiation by using the explicit template instantiation syntax (as defined in
the ANSI/ISO C++ International Standard) in your source file.
You can request explicit instantiation of a particular template class or a particular template function.
In addition, member functions and static data members of class templates may be explicitly
instantiated.
Explicit instantiation of a class instantiates all member functions and static data members of that
class, regardless of whether or not they are used.
For example, following is a request to explicitly instantiate the Table template class with char*:
template class Table<char*>;
When you specify an explicit instantiation, you are asking the compiler to instantiate a template
at the point of the explicit instantiation in the translation unit in which it occurs.
Usage
This might be useful when you are building a library for distribution and want to create a set of
compiler-generated template specializations that you know will most commonly be used. Then
when an application is linked with this library, any of these commonly used specializations need
not be instantiated.
Another scenario might be a frequently used library that contains a repository of template
specializations for your development team. Instantiating all such specializations in one, known
translation unit would allow easy maintenance when changes are needed and eliminate cases of
duplicate definition.
Performance
Although time is required to analyze and design code for explicit instantiation, compilation may
be faster than for the equivalent implicit instantiation.
Examples
Following are the examples for explicit and implicit instantiation:
Class Template
Following are examples of explicit and implicit instantiation syntax for a class template:
template <class T> class Array; // forward
// declaration
// for the
// Array class
// template
template <class T> class Array {/*...*/}; // definition
// of the Array
// class
// template
template class Array <int>; // request to
// explicitly
// instantiate
// Array<int>
// template class
Array <char> tc; // use of
// Array<char>
// template
Invoking Compile-Time Instantiation 133