An instance method that calls each other between C and C + +

  This article mainly introduces the C and C + + call each other instance method, we refer to the use of the bar

1. Export C functions for projects in C or C + +   If you are using a DLL written in C that you want to export a function to a C or C + + module, you should use the __cplusplus preprocessor macro to determine the language you are compiling. If used from a C + + language module, these functions are declared with a C link. If you use this technique and provide a header file for your DLL, these functions can be used by C and C + + modules intact.   The following code demonstrates the header files that can be used by C and C + + client applications:     Code is as follows://MyCFuncs.h #ifdef __cplusplus extern "C" { //only nee D to export C interface if              //used by C + + source code #endif   __DEC Lspec (dllimport) void Mycfunc (); __declspec (dllimport) void Anothercfunc ();   #ifdef __cplusplus} #endif       Mycfunc () and Anothercfunc () are exported functions for the C language DLL.   If you need to link a C function to a C + + executable, and the function declaration header file does not use the above technique, add the following in the C + + source file to prevent the compiler from modifying the C function name:       Code is as follows: extern "C"   {#include "MyCHeader.h"}     The code tells the compiler that "MyCHeader.h" is written in C and does not modify the C function name in the header file, otherwise the connection will not be found.   2, export C + + functions for C language Projects   If you have a function in a DLL written in C + + that you want to access from the C language module, you should declare these functions by using C links instead of C + + links. Unless otherwise specified, the C + + compiler uses the C + + type security naming convention (also known as name Decoration) and the C + + calling convention (which can be difficult to invoke from C using this calling convention).   To specify the C link, specify extern "C" for the function declaration in the DLL. For example:     Codeas follows: extern "C" __declspec (dllexport) int MyFunc (long parm1);     in C language functions can not directly invoke C + + code, if you want to call, you could do a wrapper, such as Call_lib_cppfunction, its declaration and implementation are as follows:     code is as follows:// wrapper function extern "C" void Call_lib_cppfunction (lib* p, dataattribute* dataattribute)   {    P->da Fun (Dataattribute); }   //Dafun is the implementation of our C + + code void Lib::d afun (dataattribute* dataattribute) {    map<string, mmsinfo& Gt;::iterator it;    //...}