unnecessary/unused 模板是否已实例化？
Are unnecessary/unused templates instantiated?
我有一个函数void f<int N>()。 f 仅使用模板参数 1 和 2 调用，例如f<1>() 和 f<2>() 我已经有效地将 f 专门用于这两个参数。 f 永远不会用任何其他参数调用，但我已经用一般 N 定义了 f，只是为了 "clarity"。问题：编译器是否仍会实例化 f<N>() 的这个未使用的定义？ 如果是这样，我觉得这会造成代码膨胀，因为我有许多此类函数位于程序中非常关键的性能区域。
（相反，我正在考虑注释 f<N>() 定义并将其替换为空定义，即 void f<N>(){}。）
除非使用模板，否则不会实例化模板。
来自标准：
§ 14.7.1/10
An implementation shall not implicitly instantiate a function
template, a member template, a non-virtual member function, a member
class, or a static data member of a class template that does not
require instantiation. It is unspecified whether or not an
implementation implicitly instantiates a virtual member function of a
class template if the virtual member function would not otherwise be
instantiated. The use of a template specialization in a default
argument shall not cause the template to be implicitly instantiated
except that a class template may be instantiated where its complete
type is needed to determine the correctness of the default argument.
The use of a default argument in a function call causes
specializations in the default argument to be implicitly instantiated.
我有一个函数void f<int N>()。 f 仅使用模板参数 1 和 2 调用，例如f<1>() 和 f<2>() 我已经有效地将 f 专门用于这两个参数。 f 永远不会用任何其他参数调用，但我已经用一般 N 定义了 f，只是为了 "clarity"。问题：编译器是否仍会实例化 f<N>() 的这个未使用的定义？ 如果是这样，我觉得这会造成代码膨胀，因为我有许多此类函数位于程序中非常关键的性能区域。
（相反，我正在考虑注释 f<N>() 定义并将其替换为空定义，即 void f<N>(){}。）
除非使用模板，否则不会实例化模板。
来自标准：
§ 14.7.1/10
An implementation shall not implicitly instantiate a function template, a member template, a non-virtual member function, a member class, or a static data member of a class template that does not require instantiation. It is unspecified whether or not an implementation implicitly instantiates a virtual member function of a class template if the virtual member function would not otherwise be instantiated. The use of a template specialization in a default argument shall not cause the template to be implicitly instantiated except that a class template may be instantiated where its complete type is needed to determine the correctness of the default argument. The use of a default argument in a function call causes specializations in the default argument to be implicitly instantiated.