如何调用从C C ++函数？ [英] How to call C++ function from C?

问题描述

我知道这一点。

这是C ++的调用C函数：

如果我的应用程序是在C ++和我不得不用C编写的一个库，然后我会用调用函数

If my application was in C++ and I had to call functions from a library written in C. Then I would have used

//main.cpp

extern "C" void C_library_function(int x, int y);//prototype
C_library_function(2,4);// directly using it.

这不会裂伤的名称 C_library_function 和连接器会发现在其输入* .lib文件相同的名称和问题解决。

This wouldn't mangle the name C_library_function and linker would find the same name in its input *.lib files and problem is solved.

调用C ++ C函数???

不过，我在这里延伸的是用C语言编写的大型应用程序，我需要使用的是用C ++库。 C ++的名字改编这里作祟。连接器是抱怨没有得到解决的符号。好吧，我不能使用C ++编译器在我的C项目，因为这就是打破很多其他的东西。何处是路？

But here I'm extending a large application which is written in C and I need to use a library which is written in C++. Name mangling of C++ is causing trouble here. Linker is complaining about the unresolved symbols. Well I cannot use C++ compiler over my C project because thats breaking lot of other stuff. What is the way out?

这是我使用的是MSVC的方式

By the way I'm using MSVC

推荐答案

您需要创建一个C API的暴露你的C ++ code的功能。基本上，你需要写一个声明为externC，并有一个纯C API（不使用类，例如）封装了C ++库C ++ code。然后使用您已经创建了纯C包装库。

You need to create a C API for exposing the functionality of your C++ code. Basically, you will need to write C++ code that is declared extern "C" and that has a pure C API (not using classes, for example) that wraps the C++ library. Then you use the pure C wrapper library that you've created.

您C API可以任意跟随一个面向对象的风格，即使C不是面向对象的。例如：

Your C API can optionally follow an object-oriented style, even though C is not object-oriented. Ex:

 // *.h file
 // ...
 #ifdef __cplusplus
 #define EXTERNC extern "C"
 #else
 #define EXTERNC
 #endif

 typedef void* mylibrary_mytype_t;

 EXTERNC mylibrary_mytype_t mylibrary_mytype_init();
 EXTERNC void mylibrary_mytype_destroy(mylibrary_mytype_t mytype);
 EXTERNC void mylibrary_mytype_doit(mylibrary_mytype_t self, int param);

 #undef EXTERNC
 // ...


 // *.cpp file
 mylibrary_mytype_t mylibrary_mytype_init() {
   return new MyType;
 }

 void mylibrary_mytype_destroy(mylibrary_mytype_t untyped_ptr) {
    MyType* typed_ptr = static_cast<MyType*>(untyped_ptr);
    delete typed_ptr;
 }

 void mylibrary_mytype_doit(mylibrary_mytype_t untyped_self, int param) {
    MyType* typed_self = static_cast<MyType*>(untyped_self);
    typed_self->doIt(param);
 }

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