問題描述

這個我知道.

從 C++ 調(diào)用 C 函數(shù):

如果我的應(yīng)用程序是用 C++ 編寫的，而我必須從用 C 編寫的庫中調(diào)用函數(shù).那么我會使用

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.

這不會破壞名稱 C_library_function 并且鏈接器會在其輸入的 *.lib 文件中找到相同的名稱，問題就解決了.

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.

從 C 調(diào)用 C++ 函數(shù)???

但是在這里我要擴展一個用 C 編寫的大型應(yīng)用程序，我需要使用一個用 C++ 編寫的庫.C++ 的名稱修改在這里造成了麻煩.鏈接器抱怨未解析的符號.好吧，我不能在我的 C 項目上使用 C++ 編譯器，因為那會破壞很多其他東西.出路是什么?

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?

順便說一下，我正在使用 MSVC

By the way I'm using MSVC

推薦答案

您需要創(chuàng)建一個 C API 來公開您的 C++ 代碼的功能.基本上，您將需要編寫聲明為 extern "C" 并且具有包裝 C++ 庫的純 C API(例如不使用類)的 C++ 代碼.然后使用您創(chuàng)建的純 C 包裝器庫.

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.

您的 C API 可以選擇遵循面向?qū)ο蟮娘L格，即使 C 不是面向?qū)ο蟮?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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