In the explicit instances method, instances are generated only for templates that are explicitly instantiated. Implicit instantiations are not satisfied. Instances are placed within the current compilation unit.
The advantage of this method is that you have the least amount of template compilation and smallest object sizes.
The disadvantage is that you must perform all instantiation manually.
Template instances receive global linkage. These instances are visible and usable outside the current compilation unit. The linker recognizes and discards duplicates.
Specify explicit instances with the -instances=explicit option.