According to cppref, the identity characteristics of inline
functions in multiple translation units are as follows:
...
2) It has the same address in every translation unit.
3) Function-local static objects in all function definitions are shared across all translation units (they all refer to the same object defined in one translation unit)
...
Simply speaking, a singleton identity is implied.
I'm wondering whether the same applies to function template instantiations without the inline
specifier.
The same applies to templates. See §3.2 One definition rule: