When you use the semi-explicit instances method, instances are generated only for templates that are explicitly instantiated or implicitly instantiated within the body of a template. Instances required by explicitly created instances are generated automatically. Implicit instantiations in the mainline code are not satisfied. Instances are placed within the current compilation unit. As a consequence, templates are reinstantiated during each recompilation; instances receive global linkage and they are not saved to the template repository.
Specify semi-explicit instances with the -instances=semiexplicit option.