GetProcAddress返回NULL。

Question

GetProcAddress返回NULL。

3

我需要使用来自DLL的一个简单函数；我可以加载库，但是GetProcAddress返回NULL。我想我理解了名称修饰，但也许我做错了什么。谢谢（代码如下，我会尽快添加其他所需信息）:

mydll.h

#ifdef MYDLL_EXPORTS
#define MYDLL_API extern "C" __declspec(dllexport)
#else
#define MYDLL_API extern "C" __declspec(dllimport)
#endif

MYDLL_API void testFunction(void);
MYDLL_API LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam);

mydll.cpp

#include "stdafx.h"
#include "mydll.h"

// This is an example of an exported function.
MYDLL_API void testFunction(void)
{
MessageBox(NULL, (LPCWSTR)L"Test", (LPCWSTR)L"Test", MB_OK);
}

MYDLL_API LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam)
{
// processes the message
if(nCode >= 0)
{
    if(wParam != NULL && wParam == MK_RBUTTON)
    {
        MessageBox(NULL, (LPCWSTR)L"Captured mouse right button", (LPCWSTR)L"Test", MB_OK);
    }
}

// calls next hook in chain
return CallNextHookEx(NULL, nCode, wParam, lParam);
}

来自 main.cpp 的代码

...
case WM_CREATE:
    {   
        // creates state for window
        stateClassPointer = new stateClass();
        // saves states pointer in a space reserved for user data
        SetWindowLongPtr(hWnd, GWLP_USERDATA, (LONG_PTR) stateClassPointer);

        // now it will load DLL and set up hook procedure for mouse events

        // declares local variables
        HOOKPROC hkprcMouseProc;
        HINSTANCE hinstDLL; 
        HHOOK hhookMouseProc; 
        //FARPROC WINAPI test;
        // loads DLL
        if((hinstDLL = LoadLibrary(TEXT("C:\\Users\\Francesco\\Dropbox\\poli\\bi\\not\\pds\\sp\\wk5\\lsp5\\Debug\\mydll.dll"))) == NULL)
        {
            MessageBox(hWnd, (LPCWSTR)L"Error loading DLL", (LPCWSTR)L"Error", MB_OK | MB_ICONERROR);
            break;
        }
        // saves DLL handle in the state class
        stateClassPointer->setHInstance(hinstDLL);
        // sets up hook procedure for mouse events
        if((hkprcMouseProc = (HOOKPROC)GetProcAddress(hinstDLL, "mouseProc")) == NULL)
        {
            MessageBox(hWnd, (LPCWSTR)L"Error setting windows hook: GetProcAddress", (LPCWSTR)L"Error", MB_OK | MB_ICONERROR);
            break;
        }
        if((hhookMouseProc = SetWindowsHookEx(WH_MOUSE, hkprcMouseProc, hinstDLL, 0)) == NULL)
        {
            MessageBox(hWnd, (LPCWSTR)L"Error setting windows hook: SetWindowsHookEx", (LPCWSTR)L"Error", MB_OK | MB_ICONERROR);
            break;
        }
        // saves hook handle in the state class
        stateClassPointer->setHHook(hhookMouseProc);
        /*test = GetProcAddress(hinstDLL, "testFunction");
        test();*/
    }
    break;
...

- gc5

1个回答

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- Hans Passant · Accepted Answer

是的，MessageBox()调用成功且没有错误。将GetLastError()调用放在它之前。

否则，错误是可预测的，因为它找不到"mouseProc"。该名称将在DLL中被破坏，很可能是"_mouseProc@12"。使用dumpbin.exe /exports命令检查您的DLL以确保。

Fwiw: 通过链接其导入库而不是动态加载DLL，可以使此代码更少痛苦。 DLL将被注入到其他进程中并不意味着您也必须将其注入到自己的进程中。您所需的只是模块句柄，以便可以调用SetWindowsHookEx()。从DllMain()入口点获取它或使用GetModuleHandle()。