Debug: generic related "unresolved external symbols"

We are temp.h The function is declared in temp.cpp To implement functions in , That's fine , But only limited to ordinary functions , On function template , This kind of behavior is not desirable ;

Why report a mistake

This is about the compilation and linking process , First compile temp.h file , The compiler interprets function declarations , Then the compiler will leave a marker symbol , When compiling to the implementation file , Will link its function address , But we know that , Function templates are not instantiated during compilation , So I can't find the address .

Of course , There will be no error when we do not instantiate this function , Because this is only equivalent to writing a function declaration , Functions that are not implemented , But when we implicitly instantiate the function template , You're going to report a mistake , Because the function address doesn't exist at all ;

How to solve

It's simple , We just need to put the declaration and implementation of the function together , In this way, the compiler will not address when compiling to the implementation file ;

Of course, we need to limit the scope of the function , I'm going to add a... In front of it static Modifier