Question

It is my understanding that either a declaration or typedef of a specialization ought to cause a template class to be instantiated, but this does not appear to be happening with gcc. E.g. I have a template class, template class Foo {};

I write

  class Foo<double>;  

or

typedef Foo<double> DoubleFoo;  

but after compilation the symbol table of the resulting object file does not contain the members of Foo.

If I create an instance:

Foo<double> aFoo;  

then of course the symbols are all generated.

Has anyone else experienced this and/or have an explanation?

Answer 1

The syntax for explicit instantiation is

template class Foo<double>;

See C++03 §14.7.2.

Hoping the functions get generated and linked, but not stripped after creating, but not using, an instance (the most minimal implicit instantiation), is quite a gamble.