从DLL VC ++显式调用函数 [英] Explicit calling of function from dll vc++

问题描述

大家好

我在开始执行并调用DLL中存在的函数的主文件中具有以下代码.

Hello everyone

I have the following code in main file from where i start execution and call the function present in DLL.

#include "stdafx.h"
#include "windows.h"
#include "conio.h"
#include "windef.h"


int _tmain(int argc, _TCHAR* argv[])
{
	
	HINSTANCE instcall=LoadLibrary(TEXT("c:\\test2.dll"));
	if(instcall==NULL)
	printf("Failed to load dll");
	FARPROC getproc=GetProcAddress(instcall,"funcall");
	if(getproc==NULL)
	printf("failed entry point");
	typedef int(__stdcall * picFunc)();
	picFunc funcall;
        funcall=picFunc(getproc);
	funcall();
getch();
//LPTSTR path=(LPTSTR)"c:\test2.dll";
	/*system("notepad.exe");
	DWORD threadId=dwThredId*/
/*typedef void *(_stdcall *creatfn)();
	creatfn myfunc=(creatfn) GetProcAddress(instcall,"call");
	void *objptr=myfunc();*/

	/*picFunc funcall;*/
//=picFunc(getproc);
	//funcall();
	///call=mycall(getproc);
}

dll的代码在这里:

The code of dll is here:

 // test2.cpp : Defines the exported functions for the DLL application.
//

#include "stdafx.h"
#include "stdio.h"
#include "conio.h"

 void funcall()
{
	printf("hello");
}

当我执行要获取的代码时，test1.exe中0x00000000的未处理异常:0xC0000005:访问冲突读取位置0x00000000.并且输出将是失败的入口点....我正在使用Visual Studio 2008进行执行.

任何人都可以帮助我解决这个问题，我是系统编程的新手.同时也请推荐一本学习系统编程的好书.我有基本的C ++知识.


谢谢大家

When i execute the code i am getting, Unhandled exception at 0x00000000 in test1.exe: 0xC0000005: Access violation reading location 0x00000000. And the output will be failed entry point.... I am using Visual studio 2008 for execution.

CAn anyone please help me in sorting out this problem i am newbie to system programming. And also please suggest good book for learning system programming. I have the knowledge of basic C++.


THank you all

推荐答案

GetProcAddress可能会返回NULL.
您应该将funcall标记为要导出:
http://msdn.microsoft.com/en-us/library/3y1sfaz2 (v = vs.71).aspx [

GetProcAddress proporbly returns NULL.
you should mark funcall for export:
http://msdn.microsoft.com/en-us/library/3y1sfaz2(v=vs.71).aspx[^]

您的代码有缺陷；如果您的任何函数调用失败，您将打印一条错误消息，然后像执行成功一样继续执行.遇到失败情况时，您需要脱离main().

Your code is flawed; if any of your function calls fail you print an error message, but then continue execution as if they had succeeded. You need to break out of main() when you get a fail condition.

除了Richard和Simon说的话:

有多种方法可以将功能标记为已导出.由于诸如名称修改之类的事情，您不应该假定导出的名称是"funcall"，请参见 http ://en.wikipedia.org/wiki/Name_mangling [ ^ ].

您可以使用"extern C {...}"，但也可以使用某些二进制转储工具(例如dumpbin.exe)检查实际导出的内容.您可以从Visual Studio命令提示符运行它.请参阅 http://msdn.microsoft.com/en-us/library/c1h23y6c(v = vs.71).aspx [

In addition to what Richard and Simon say:

There is more than one way to mark a function as exported. You should not assume that the exported name is "funcall", because of such thing as name mangling, see http://en.wikipedia.org/wiki/Name_mangling[^].

You can use "extern C {...}", but also you can check what actually was exported using some binary dump tool such as dumpbin.exe. You can run it from Visual Studio Command Prompt. See http://msdn.microsoft.com/en-us/library/c1h23y6c(v=vs.71).aspx[^].

—SA

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