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POHow to pass variables to function exported by a DLL, I get error LNK2001
 

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  1. POHow to pass variables to function exported by a DLL, I get error LNK2001
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    <p>I have to pass a HWND variable from the main program to a function exported by a DLL. Variable is called mainHwnd and DLL is defined in this way:</p> <p><strong>mydll.h</strong></p> <pre><code>#ifdef MYDLL_EXPORTS #define MYDLL_API extern "C" __declspec(dllexport) #else #define MYDLL_API extern "C" __declspec(dllimport) #endif MYDLL_API HWND mainHwnd; MYDLL_API void testFunction(void); MYDLL_API LRESULT CALLBACK mouseProc(int nCode, WPARAM wParam, LPARAM lParam); </code></pre> <p><strong>mydll.cpp</strong></p> <pre><code>#include "stdafx.h" #include "mydll.h" #include &lt;string&gt; #define CLASSNAMELEN 5 MYDLL_API HWND mainHwnd = 0; // 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 &gt;= 0) { if(wParam != NULL &amp;&amp; (wParam == WM_RBUTTONDOWN || wParam == WM_RBUTTONUP)) { std::wstring s; MessageBox(NULL, (LPCWSTR)L"Captured mouse right button", (LPCWSTR)L"Test", MB_OK); MOUSEHOOKSTRUCT *m = (MOUSEHOOKSTRUCT*) lParam; GetClassName(m-&gt;hwnd, (LPWSTR) s.c_str(), CLASSNAMELEN); if(s == L"Edit") SendMessage(mainHwnd, WM_APP, 0, (LPARAM) lParam); } } // calls next hook in chain return CallNextHookEx(NULL, nCode, wParam, lParam); } </code></pre> <p><strong>main program</strong></p> <pre><code>MYDLL_API HWND mainHwnd; ... case WM_CREATE: { // now it will load DLL and set up hook procedure for mouse events // declares local variables HOOKPROC hkprcMouseProc; HINSTANCE hinstDLL; HHOOK hhookMouseProc; // 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 main window handle for DLL functions mainHwnd = hWnd; ... </code></pre> <p>Compiling I get </p> <pre><code>error LNK2001: unresolved external symbol __imp__mainHwnd </code></pre> <p>while using dumpbin /exports mydll.dll I get that global variable name is mangled as:</p> <pre><code>mainHwnd = _mainHwnd </code></pre> <p>I went through a lot of pages on google with no results. Maybe there is a conceptual error.. Thanks</p>
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