“不完整类型的无效使用"部分模板特化错误 [英] "invalid use of incomplete type" error with partial template specialization

问题描述

以下代码:

template <typename S, typename T>
struct foo {
   void bar();
};

template <typename T>
void foo <int, T>::bar() {
}

给我错误

invalid use of incomplete type 'struct foo<int, T>'
declaration of 'struct foo<int, T>'

(我正在使用 gcc.)我的部分专业化语法错误​​吗?请注意，如果我删除第二个参数:

(I'm using gcc.) Is my syntax for partial specialization wrong? Note that if I remove the second argument:

template <typename S>
struct foo {
   void bar();
};

template <>
void foo <int>::bar() {
}

然后它就可以正确编译了.

then it compiles correctly.

推荐答案

你不能部分特化一个函数.如果您希望在成员函数上这样做，则必须部分特化整个模板(是的，这很烦人).在大型模板化类上，要部分专门化一个函数，您需要一种解决方法.也许模板成员结构(例如 template struct Nested)会起作用.或者，您可以尝试从另一个部分专门化的模板派生(如果您使用 this->member 表示法，则可以使用，否则您会遇到编译器错误).

You can't partially specialize a function. If you wish to do so on a member function, you must partially specialize the entire template (yes, it's irritating). On a large templated class, to partially specialize a function, you would need a workaround. Perhaps a templated member struct (e.g. template <typename U = T> struct Nested) would work. Or else you can try deriving from another template that partially specializes (works if you use the this->member notation, otherwise you will encounter compiler errors).

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