菜鸟请教dll显式加载问题

[ashlet]

typedef void SRPROC(void);
HINSTANCE hInst;
SRPROC *pFun;
VERIFY(hInst =::LoadLibrary("Ex5_Win32.dll"));
VERIFY(pFun = (SRPROC*)::GetProcAddress(hInst,"Msg"));
(*pFun)();
我是想调用一个void fun(void)形函数的，但是出错了。那个函数隐式调用是没有出错的，证明dll那边OK，那究竟是那里出错了呢？

[wanilyer]

(*pFun)();
把这个改成 pFun();

[ashlet]

老哥还是不行哦

[wanilyer]

HINSTANCE hInst = LoadLibrary("User32.DLL");

if(hInst)
{
typedef BOOL (WINAPI *MYFUNC)(HWND,COLORREF,BYTE,DWORD);
MYFUNC fun = NULL;

//È¡µÃSetLayeredWindowAttributesº¯ÊýÖ¸Õë
fun=(MYFUNC)GetProcAddress(hInst, "SetLayeredWindowAttributes");

if(fun)
{
fun(this->GetSafeHwnd(), 0, nInAlpha, 2);
}

FreeLibrary(hInst);
}

给你一段源代码，你自己照猫画虎吧！

[wanilyer]

HINSTANCE hInst = LoadLibrary("User32.DLL");

if(hInst)
{
typedef BOOL (WINAPI *MYFUNC)(HWND,COLORREF,BYTE,DWORD);
MYFUNC fun = NULL;

fun=(MYFUNC)GetProcAddress(hInst, "SetLayeredWindowAttributes");

if(fun)
{
fun(this->GetSafeHwnd(), 0, nInAlpha, 2);
}

FreeLibrary(hInst);
}

[ashlet]

HINSTANCE hInst = LoadLibrary("Ex5_Win32.dll");
if(!hInst)
{
MessageBox("NL","NL");
FreeLibrary(hInst);
}

if(hInst)
{
typedef float (*MYFUNC)(float,float);
MYFUNC fun = NULL;

FARPROC hfun;
hfun = GetProcAddress(hInst, "Msg");
if(hfun)
{
MessageBox("load","load");
}
else
{
MessageBox("No load","No load");
}
//fun=(MYFUNC)GetProcAddress(hInst, "addfloat");
fun = (MYFUNC)hfun;
if(!fun)
{
MessageBox("NG","NG");
}
if(fun)
{
CString str;
float i = fun(5.0,8.0);
str.Format("res=%f",i);
CEdit *et1 = (CEdit *)this->GetDlgItem(IDC_EDIT1);
et1->SetWindowText(str);
}

FreeLibrary(hInst);
}

/*CString str;
float i = addfloat(1,1);
str.Format("%f",i);
CEdit *et1 = (CEdit *)this->GetDlgItem(IDC_EDIT1);
et1->SetWindowText(str);
Msg();
Msg2();*/

[ashlet]

/*#pragma comment(lib,"Ex5_Win32.lib")
_declspec(dllimport) float addfloat(float x,float y);
_declspec(dllimport) int addint(int x,int y);
_declspec(dllimport) void Msg(void);
_declspec(dllimport) int Msg2(void);*/

/*CString str;
float i = addfloat(1,1);
str.Format("%f",i);
CEdit *et1 = (CEdit *)this->GetDlgItem(IDC_EDIT1);
et1->SetWindowText(str);
Msg();
Msg2();*/

去掉那些注释，用隐式的话是OK的

但是用上面的代码运行结果是
not load
NG

[ashlet]

请问该怎么改

[whwjn]

你的dll里面有没有导出Msg这个函数啊？用dumpbin看一看导出来了没有？

[ashlet]

// Ex5_Win32dll.cpp : Defines the entry point for the DLL application.
//

#include "stdafx.h"

#define DLLEP __declspec(dllexport)
BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
return TRUE;
}

DLLEP void Msg(void)
{
MessageBox(NULL,"void(*)(void)"," ",MB_OK);
}
DLLEP int Add(int x,int y)
{
return x+y;
}

DLLEP int RetInt(int x)
{
return x;
}
/////////////以上是dll
void CDLL_TDlg::OnButton1()
{

//typedef int (* LPFNDLLFUNC1)(int);
//typedef int (* LPFNDLLFUNC1)(int,int);


HINSTANCE hDLL; // Handle to DLL
//LPFNDLLFUNC1 lpfnDllFunc1; // Function pointer

hDLL = LoadLibrary("Ex5_Win32dll.dll");
if (hDLL != NULL)
{
//lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL,"?RetInt@@YAHH@Z");
//lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL,"?Add@@YAHHH@Z");
void (*lpfnDllFunc1)();
lpfnDllFunc1 = (void(*)())GetProcAddress(hDLL,"?Msg@@YAXXZ");

if (!lpfnDllFunc1)
{
MessageBox("not load fun");
// handle the error

return ;
}
else
{
// call the function

lpfnDllFunc1();
/*CString temp;
int i = lpfnDllFunc1(100,50);
temp.Format("%d",i);
MessageBox(temp);*/
}
FreeLibrary(hDLL);
}
else
{
AfxMessageBox("no load dll");
}


}
以下是调用部分。
为什么我用GetProcAddress(hDLL,"Msg");GetProcAddress(hDLL,"Add");这样取不到函数地址，而一定要像上面那样？
"?RetInt@@YAHH@Z"这些就是用dumpbin看到的。
为什么我写的就不能像书上那样直接用Msg，Add这些名字呢？是那里出了什么错误吗？起高手赐教。

[火麒噬日]

留个记号

[whwjn]

那是C++ 的mangled name现象,把
DLLEP void Msg(void)
{
MessageBox(NULL,"void(*)(void)"," ",MB_OK);
}
改成
extern "C" DLLEP void Msg(void)
{
MessageBox(NULL,"void(*)(void)"," ",MB_OK);
}
应该就OK了。
看看这篇文章：
http://www.lzu.edu.cn/netteach/jiaochen/c++/ch5/chap52.htm