subject_27296.htm

一些关于vc的问答

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序号：27296 发表者：mkyong 发表日期：2003-01-10 09:13:36
<br>主题：DLL explicit dynaimic linking problem
<br>内容：when i click leftmouse, i got this message"Unable to locate the function", why i can't get the function address?<BR>i already put the mydll.dll file in the same folder and some PATH environment variable folder, but still can't working....<BR>please....<BR><BR>/***********mydll.cpp*****************/<BR><BR>#include&lt;windows.h&gt;<BR>#include"mydll.h"<BR>void ShowMousePos(HDC hDC, LPARAM lParam)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;char str[80];<BR>&nbsp;&nbsp;&nbsp;&nbsp;wsprintf(str,"Button position is %d, %d", LOWORD(lParam),HIWORD(lParam));<BR>&nbsp;&nbsp;&nbsp;&nbsp;TextOut(hDC,LOWORD(lParam),HIWORD(lParam),str,strlen(str));<BR>}<BR><BR>/******mydll.h************/<BR><BR>#define DllExport __declspec(dllexport)<BR>DllExport void ShowMousePos(HDC hDC,LPARAM lParam);<BR><BR><BR>/*******ExplicitDll.cpp( Win32 implement dll file)************/<BR><BR>long FAR PASCAL WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;HDC hDC;<BR>&nbsp;&nbsp;&nbsp;&nbsp;HMODULE hLibrary;<BR><BR>&nbsp;&nbsp;&nbsp;&nbsp;typedef void (*func)(HDC,LPARAM);<BR>&nbsp;&nbsp;&nbsp;&nbsp;func f;<BR>&nbsp;&nbsp;&nbsp;&nbsp;hLibrary = LoadLibrary("mydll");<BR>&nbsp;&nbsp;&nbsp;&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;if(!hLibrary)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MessageBox(hwnd,"Cannot Load Library","Error",MB_OK);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return 0;<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR>&nbsp;&nbsp;&nbsp;&nbsp;switch(msg)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;case WM_LBUTTONDOWN:<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;hDC = GetDC(hwnd);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f = (func) GetProcAddress(hLibrary, "ShowMousePos");<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(!f)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MessageBox(hwnd,"Unable to locate the function","Error",MB_OK);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return 0;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;f(hDC,lParam);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ReleaseDC(hwnd,hDC);<BR>&nbsp;&nbsp;&nbsp;&nbsp;case WM_DESTROY:<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;FreeLibrary(hLibrary);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PostQuitMessage(0);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break;<BR>&nbsp;&nbsp;&nbsp;&nbsp;default:<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return DefWindowProc(hwnd,msg,wParam,lParam);<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR>&nbsp;&nbsp;&nbsp;&nbsp;return 0;<BR>}
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回复者：bb 回复日期：2003-01-10 09:34:56
<br>内容：应为hLibrary = LoadLibrary("mydll.dll");<BR>
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回复者：mkyong 回复日期：2003-01-10 19:42:39
<br>内容：应为hLibrary = LoadLibrary("mydll.dll");<BR><BR>What means, can u explain more clearly. Thx
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回复者：tjhe 回复日期：2003-01-10 22:47:52
<br>内容：use full file name of the dll: hLibrary = LoadLibrary("mydll.dll");<BR>
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回复者：mkyong 回复日期：2003-01-11 11:56:48
<br>内容：try already lah, still can't working.<BR>i think not the LoadLibrary() problem, coz i didn't get the<BR>"Cannot Load Library" Message.<BR><BR>i think may be GetProcAddress() problem coz i can't get the function address......<BR> 
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<font color=red>答案被接受</font><br>回复者：cool 回复日期：2003-01-13 11:46:07
<br>内容：#include&lt;windows.h&gt;<BR>#include"mydll.h"<BR>extern "C" __declspec(dllexport) void ShowMousePos(HDC hDC, LPARAM lParam)<BR>^^^^^^^^^^^<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;char str[80];<BR>&nbsp;&nbsp;&nbsp;&nbsp;wsprintf(str,"Button position is %d, %d", LOWORD(lParam),HIWORD(lParam));<BR>&nbsp;&nbsp;&nbsp;&nbsp;TextOut(hDC,LOWORD(lParam),HIWORD(lParam),str,strlen(str));<BR>}<BR><BR>/******mydll.h************/<BR><BR>//#define DllExport __declspec(dllexport)<BR>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^<BR>extern "C" __declspec(dllexport) void ShowMousePos(HDC hDC,LPARAM lParam);<BR>^^^^^^^^^^<BR><BR><BR><BR>/*******ExplicitDll.cpp( Win32 implement dll file)************/<BR><BR><BR>typedef void DLLFUNC(HDC,LPARAM);<BR>DLLFUNC *f;<BR>f = (DLLFUNC *) GetProcAddress(hLibrary, "ShowMousePos");<BR><BR>try it<BR><BR><BR><BR> <BR><BR><BR><BR>2003-1-13 15:35:56