从c++调用DLL中的函数-CallingfunctionsinaDLLfromC++

20  

There are many ways to do this but I think one of the easiest options is to link the application to the DLL at link time and then use a definition file to define the symbols to be exported from the DLL.

有很多方法可以做到这一点，但我认为最简单的方法之一是在链接时将应用程序链接到DLL，然后使用定义文件定义要从DLL导出的符号。

CAVEAT: The definition file approach works bests for undecorated symbol names. If you want to export decorated symbols then it is probably better to NOT USE the definition file approach.

注意:定义文件方法对于未修饰的符号名称效果最好。如果您想要导出装饰符号，那么最好不要使用定义文件方法。

Here is an simple example on how this is done.

这里有一个简单的例子说明如何实现这一点。

Step 1: Define the function in the export.h file.

步骤1:在导出中定义函数。h文件。

int WINAPI IsolatedFunction(const char *title, const char *test);

Step 2: Define the function in the export.cpp file.

步骤2:在导出中定义函数。cpp文件。

#include 

int WINAPI IsolatedFunction(const char *title, const char *test)
{
    MessageBox(0, title, test, MB_OK);
    return 1;
}

Step 3: Define the function as an export in the export.def defintion file.

步骤3:将函数定义为出口.def定义文件中的导出。

EXPORTS    IsolatedFunction          @1

Step 4: Create a DLL project and add the export.cpp and export.def files to this project. Building this project will create an export.dll and an export.lib file.

步骤4:创建一个DLL项目并添加导出。cpp和export.def文件到这个项目。构建这个项目将创建一个导出。dll和出口。lib文件。

The following two steps link to the DLL at link time. If you don't want to define the entry points at link time, ignore the next two steps and use the LoadLibrary and GetProcAddress to load the function entry point at runtime.

以下两个步骤在链接时链接到DLL。如果您不想在链接时定义入口点，请忽略接下来的两个步骤，并使用LoadLibrary和GetProcAddress在运行时加载函数入口点。

Step 5: Create a Test application project to use the dll by adding the export.lib file to the project. Copy the export.dll file to ths same location as the Test console executable.

步骤5:创建一个测试应用程序项目，通过添加导出来使用dll。项目的库文件。复制导出。dll文件到与测试控制台可执行文件相同的位置。

Step 6: Call the IsolatedFunction function from within the Test application as shown below.

步骤6:从测试应用程序中调用隔离函数，如下所示。

#include "stdafx.h"

// get the function prototype of the imported function
#include "../export/export.h"

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
    // call the imported function found in the dll
    int result = IsolatedFunction("hello", "world");

    return 0;
}

9  

Can also export functions from dll and import from the exe, it is more tricky at first but in the end is much easier than calling LoadLibrary/GetProcAddress. See MSDN.

也可以从dll中导出函数并从exe中导入函数，这在一开始是比较棘手的，但最终比调用LoadLibrary/GetProcAddress要容易得多。看到MSDN。

When creating the project with the VS wizard there's a check box in the dll that let you export functions.

在使用VS向导创建项目时，dll中的一个复选框允许您导出函数。

Then, in the exe application you only have to #include a header from the dll with the proper definitions, and add the dll project as a dependency to the exe application.

然后，在exe应用程序中，您只需要在dll中包含一个包含适当定义的标题，并将dll项目添加为exe应用程序的依赖项。

Check this other question if you want to investigate this point further Exporting functions from a DLL with dllexport.

如果您想进一步研究这一点，请检查另一个问题，即从使用dllexport的DLL中导出函数。

6  

You can either go the LoadLibrary/GetProcAddress route (as Harper mentioned in his answer, here's link to the run-time dynamic linking MSDN sample again) or you can link your console application to the .lib produced from the DLL project and include the hea.h file with the declaration of your function (as described in the load-time dynamic linking MSDN sample)

您可以使用LoadLibrary/GetProcAddress路径(正如Harper在他的回答中提到的，这里是到运行时动态链接MSDN示例的链接)，也可以将控制台应用程序链接到从DLL项目生成的.lib并包含hea。带有函数声明的h文件(如载时动态链接MSDN示例所述)

In both cases, you need to make sure your DLL exports the function you want to call properly. The easiest way to do it is by using __declspec(dllexport) on the function declaration (as shown in the creating a simple dynamic-link library MSDN sample), though you can do it also through the corresponding .def file in your DLL project.

在这两种情况下，您都需要确保您的DLL输出您想要正确调用的函数。最简单的方法是在函数声明中使用__declspec(dllexport)(如创建一个简单的动态链接库MSDN示例所示)，不过你也可以通过DLL项目中相应的.def文件来实现。

For more information on the topic of DLLs, you should browse through the MSDN About Dynamic-Link Libraries topic.

有关dll主题的更多信息，请浏览MSDN关于动态链接库主题。

3  

The following are the 5 steps required:

以下是所需的5个步骤:

1. declare the function pointer
2. 声明函数指针
3. Load the library
4. 加载库
5. Get the procedure address
6. 得到程序地址
7. assign it to function pointer
8. 将它赋值给函数指针。
9. call the function using function pointer
10. 使用函数指针调用函数

You can find the step by step VC++ IDE screen shot at http://www.softwareandfinance.com/Visual_CPP/DLLDynamicBinding.html

您可以在http://www.softwareandfinance.com/Visual_CPP/DLLDynamicBinding.html中找到逐步的vc++ IDE截图

Here is the code snippet:

下面是代码片段:

int main()
{
/***
__declspec(dllimport) bool GetWelcomeMessage(char *buf, int len); // used for static binding
 ***/
    typedef bool (*GW)(char *buf, int len);

    HMODULE hModule = LoadLibrary(TEXT("TestServer.DLL"));
    GW GetWelcomeMessage = (GW) GetProcAddress(hModule, "GetWelcomeMessage");

    char buf[128];
    if(GetWelcomeMessage(buf, 128) == true)
        std::cout <