why template base class is not forced to be instantiated

Asked Jul 04 '22 at 15:18

Active Jul 04 '22 at 16:53

Viewed 63 times

I have 2 template classes and one inherit from the other.

template <class T>
class X {
    public:
    int get() { return 1; }
};

template <class T>
class B : public X<T> {};

// Force B instantiation would expect X to be forced as well
template class B<int>;

// If I remove next line, no code is emitted for X
template class X<int>

When forcing the template instantiation of B, the X is not instantiated as well ( see https://godbolt.org/z/3vvenM8j4)

What is the reason for that?

Note: This is a follow up to how to force instantiation of a template class used with a type alias

I would expect the given solution to work but is does not

edited Jul 04 '22 at 16:53

asked Jul 04 '22 at 15:18

OznOg

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Maybe already answered here https://stackoverflow.com/a/3712309/2001017 – Picaud Vincent Jul 04 '22 at 15:45
I can definitely do `B b; b.get();` in main without explicit instantiation. – lorro Jul 04 '22 at 15:46
@MarekR, while `T` is often used, `ALL_UPPERCASE` identifiers are often reserved to macros, so I wouldn't recommend its use. Let the standard library inspire you concerning the naming instead. – Ulrich Eckhardt Jul 04 '22 at 16:03

why template base class is not forced to be instantiated

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