问题描述

休息几周后，我试图通过模板–一书来扩展和扩展我的模板知识.David Vandevoorde 和 Nicolai M. Josuttis 的完整指南，我现在想了解的是模板的显式实例化.

After few weeks break, I'm trying to expand and extend my knowlege of templates with the book Templates – The Complete Guide by David Vandevoorde and Nicolai M. Josuttis, and what I'm trying to understand at this moment is explicit instantiation of templates.

我实际上对这种机制没有任何问题，但我无法想象我想要或想要使用此功能的情况.如果有人能向我解释这一点，我将不胜感激.

I don't actually have a problem with the mechanism as such, but I can't imagine a situation in which I would like or want to use this feature. If anyone can explain that to me I will be more than grateful.

推荐答案

直接复制自 https://docs.microsoft.com/en-us/cpp/cpp/explicit-instantiation:

您可以使用显式实例化来创建模板化类或函数的实例化，而无需在代码中实际使用它.由于这在您创建使用模板进行分发的库 (.lib) 文件时很有用，因此未实例化的模板定义不会放入对象 (.obj) 文件中.

You can use explicit instantiation to create an instantiation of a templated class or function without actually using it in your code. Because this is useful when you are creating library (.lib) files that use templates for distribution, uninstantiated template definitions are not put into object (.obj) files.

(例如，libstdc++ 包含 std::basic_string<char,char_traits<char>,allocator<char> >(即 std::stringcode>) 所以每次使用 std::string 的函数时，不需要将相同的函数代码复制到对象中.编译器只需要将它们引用(链接)到 libstdc++.)

(For instance, libstdc++ contains the explicit instantiation of std::basic_string<char,char_traits<char>,allocator<char> > (which is std::string) so every time you use functions of std::string, the same function code doesn't need to be copied to objects. The compiler only need to refer (link) those to libstdc++.)

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