inner template class specialization

[Christof Warlich]

Hi,

I need to specialize an inner template class, but gcc
refuses to compile. Here is a minimal example exposing the issue:

template<int astruct Outer {
template<int bstruct Inner {
};
};
template<int atemplate<struct Outer<a>::Inner<0{
};

gcc reports:

$ g++ -c inner.cc
inner.cc:5: error: invalid explicit specialization before ?>? token
inner.cc:5: error: enclosing class templates are not explicitly specialized
inner.cc:5: error: template parameters not used in partial specialization:
inner.cc:5: error: 'a'

Is this a gcc-specific bug or am I doing something wrong?

Thanks,

Christof

[Markus Moll]

Hi

Christof Warlich wrote:

$ g++ -c inner.cc
inner.cc:5: error: invalid explicit specialization before ?>? token
inner.cc:5: error: enclosing class templates are not explicitly
specialized inner.cc:5: error: template parameters not used in partial
specialization:
inner.cc:5: error: 'a'

Is this a gcc-specific bug or am I doing something wrong?

It's not a bug. You are not allowed to explicitly specialize the inner
template that way ("the declaration shall not explicitly specialize a class
member template if its enclosing class templates are not explicitly
specialized as well", 14.7.3/18)

Markus

[Christof Warlich]

Markus Moll schrieb:

It's not a bug. You are not allowed to explicitly specialize the inner
template that way ("the declaration shall not explicitly specialize a class
member template if its enclosing class templates are not explicitly
specialized as well", 14.7.3/18)

Does this mean that specialization of an inner class does not work at all?
I tried several things, but without success.

Nevertheless, your wording:

You are not allowed to explicitly specialize the inner template "that way"

gives me some hope that it _is_ possible. Any ideas how to do it right?

Thanks for any help,

Christof

[Christof Warlich]

Christof Warlich schrieb:

Nevertheless, your wording:

You are not allowed to explicitly specialize the inner template "that

way"

gives me some hope that it _is_ possible. Any ideas how to do it right?

Just found the solution myself:

template<int astruct Outer {
template<int b, int dummystruct Inner {
};
};
template<int a>
template<int dummy>
struct Outer<a>::Inner<0, dummy{
};

Again, thanks for your help, it just gave the hint that I was in need for :-).