Why in a C++ template, declaring a vector<T> member variable as static will produce linker error but inline static will not?

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65897259/why-in-a-c-template-declaring-a-vectort-member-variable-as-static-will-prod

Answer 1

Static members must be defined (initialized) outside their class.

Simply write in your implementation:

template<class T> std::vector<T> FooTemplate<T>::t = [some initializer];

EDIT: You do not actually need to explicitely initialize them (unless they are objects of a class without a default constructor), but you do need to repeat their declaration like this anyway.