c++ - 是否可以在 DLL 中导出具有 C 链接的 C++ 成员方法？

Question

在 cpp 文件中考虑这一点:

struct someStruct{
    public:
    extern "C"  __declspec(dllexport) int sumup();
} someStruct;

extern "C" __declspec(dllexport) int someStruct::sumup()
{
    return 0;
}

这不会编译:错误:字符串常量之前预期有不合格的 id 是否无法通过 C 链接导出 C++ 成员方法？

Answer 1

首先，链接规范不适用于成员函数；通过 [dcl.link]/4:

[...] A linkage-specification shall occur only in namespace scope (3.3). [...]

但是标准中甚至有一个与您的问题在某种程度上相关的示例，在同一段落中:

[...] A C language linkage is ignored in determining the language linkage of the names of class members and the function type of class member functions. [Example:

extern "C" typedef void FUNC_c();
class C {
  void mf1(FUNC_c*);      // the name of the function mf1 and the member
                          // function’s type have C ++ language linkage; the
                          // parameter has type pointer to C function
  FUNC_c mf2;             // the name of the function mf2 and the member
                          // function’s type have C ++ language linkage
  static FUNC_c* q;       // the name of the data member q has C ++ language
                          // linkage and the data member’s type is pointer to
                          // C function
};

extern "C" {
  class X {
    void mf();            // the name of the function mf and the member
                          // function’s type have C ++ language linkage
    void mf2(void(*)());  // the name of the function mf2 has C ++ language
                          // linkage; the parameter has type pointer to
                          // C function
  }
};

— end example]