extern C 不能在类级别使用?

问题描述

只是想确认在Windows环境下，VSTS 2008 + C++项目中，我们只能将extern C应用到函数级别，不能应用到类级别(所以类中的所有成员函数都使用C语言名称mangling)?试了好几种方法，总是编译错误.

Just want to confirm in Windows environment, VSTS 2008 + C++ project, we could only apply extern C to function level, not be able to apply to class level (so that all member functions from the class use C language name mangling)? I have tried several ways, but always compile error.

提前致谢，乔治

推荐答案

您可以通过一种非常复杂(但完全合法)的 hack 将 extern "C" 应用于成员函数:

You can sort of apply extern "C" to a member function via a very convoluted (but entirely legal) hack:

extern "C" typedef int bar_t(int x);

struct foo {
     bar_t bar; // yes, this declares a nonstatic member function!
};

int foo::bar(int x) { return x; } // definition

根据 ISO C++03 9.3[class.mfct]/9，这是可能的:

This is possible according to ISO C++03 9.3[class.mfct]/9:

可以使用函数类型的 typedef 声明(但未定义)成员函数.结果成员函数的类型与显式提供函数声明符时的类型完全相同，参见 8.3.5.

a member function can be declared (but not defined) using a typedef for a function type. The resulting member function has exactly the same type as it would have if the function declarator were provided explicitly, see 8.3.5.

然而，由于 ISO C++03 7.5[dcl.link]/4，这并没有真正给你带来任何好处:

However, this doesn't really buy you anything, because of ISO C++03 7.5[dcl.link]/4:

忽略类成员和成员函数的名称的 C 语言链接类成员函数的类型.

A C language linkage is ignored for the names of class members and the member function type of class member functions.

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