How does C++ link template instances

Question

If I define a function (maybe a class member function but not inlined) in a header file that is included by two different translation units I get a link error since that fun

Answer 1

All template functions are implicitly inline. Just as methods defined in the class declaration are implicitly inline.

When I say implicitly inline I mean the more modern usage of the word. See my lengthy description here.

In short, inline, static, and extern are all sibling linkage directives. inline tells the linker to ignore duplicate definitions of a function. Generally this means the linker will pick one definition and use it for all compilation units. I don't know of any compilers that do or did leave all duplicate template code in the final executable.

Where are template instantiations stored?
They are stored in the same way in the same place as inline functions. The details of that are compiler specific.