Why can templates only be implemented in the header file?答案

【问题标题】：Why can templates only be implemented in the header file?Why can templates only be implemented in the header file?
【发布时间】：2022-12-02 13:12:04
【问题描述】：

Quote from The C++ standard library: a tutorial and handbook:

The only portable way of using templates at the moment is to implement them in header files by using inline functions.

Why is this?

(Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)

While it is true that placing all template function definitions into the header file is probably the most convenient way to use them, it is still not clear what\'s \"inline\" doing in that quote. There\'s no need to use inline functions for that. \"Inline\" has absolutely nothing to do with this.
Book is out of date.
A template is not like a function which can be compiled into byte code. It is just a pattern to generate such a function. If you put a template on its own into a *.cpp file, there is nothing to compile. Moreover, the explicite instanciation is actually not a template, but the starting point to make a function out of the template which ends up in the *.obj file.
Am I the only one who feels that the template concept is crippled in C++ due to this?...
@AnT perhaps they meant \"inline\" not as the keyword but rather as \"methods implemented at the place of declaration, inside the class\".

标签： c++ templates undefined-reference c++-faq

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