[Bug c++/120499] import std: indirect use of an exported class using a vector yields undefined symbol

[nshead at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120499

--- Comment #2 from Nathaniel Shead <nshead at gcc dot gnu.org> ---
The issue appears to be some confusion over which TU is reponsible for
instantiating the destructor of the existing specialisation 'vector<int>': the
main file thinks that it's already been instantiated because it's a complete
type, but nothing in Coll or std uses the destructor explicitly so it ends up
never getting emitted.

Adding a user-provided destructor to 'Coll' can workaround the issue until this
gets fixed, as in:

  export class Coll {
    std::vector<int> vals;
  public:
    ~Coll() {}
  };