C++ unresolved external symbol _main referenced in function "int __cdecl invoke_main(void)"

Question

ifndef UNICODE

define UNICODE

endif

include <windows.h>

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow)
{
// Register the window class.
const wchar_t CLASS_NAME[] = L"Sample Window Class";

WNDCLASS wc = { };  

wc.lpfnWndProc = WindowProc;  
wc.hInstance = hInstance;  
wc.lpszClassName = CLASS_NAME;  

RegisterClass(&wc);  

// Create the window.  

HWND hwnd = CreateWindowEx(  
    0,                              // Optional window styles.  
    CLASS_NAME,                     // Window class  
    L"Learn to Program Windows",    // Window text  
    WS_OVERLAPPEDWINDOW,            // Window style  

    // Size and position  
    CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,  

    NULL,       // Parent window      
    NULL,       // Menu  
    hInstance,  // Instance handle  
    NULL        // Additional application data  
);  

if (hwnd == NULL)  
{  
    return 0;  
}  

ShowWindow(hwnd, nCmdShow);  

// Run the message loop.  

MSG msg = { };  
while (GetMessage(&msg, NULL, 0, 0) > 0)  
{  
    TranslateMessage(&msg);  
    DispatchMessage(&msg);  
}  

return 0;  

}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_DESTROY:
PostQuitMessage(0);
return 0;

case WM_PAINT:  
{  
    PAINTSTRUCT ps;  
    HDC hdc = BeginPaint(hwnd, &ps);  

    // All painting occurs here, between BeginPaint and EndPaint.  

    FillRect(hdc, &ps.rcPaint, (HBRUSH)(COLOR_WINDOW + 1));  

    EndPaint(hwnd, &ps);  
}  
return 0;  

}  
return DefWindowProc(hwnd, uMsg, wParam, lParam);  

}

List item

Answer 1

Change :
[Linker] [System]
Windows (/SUBSYSTEM:WINDOWS)

Answer 2

Hi @zoucyn ,

It seems that your code is missing the main function. After adding the main function, the program no longer reports any errors.

#ifndef UNICODE  
#define UNICODE  
#endif  
  
  
#include <windows.h>  
  
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);  
  
  
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow)  
{  
    // Register the window class.  
    const wchar_t CLASS_NAME[] = L"Sample Window Class";  
  
    WNDCLASS wc = { };  
    wc.lpfnWndProc = WindowProc;  
    wc.hInstance = hInstance;  
    wc.lpszClassName = CLASS_NAME;  
    RegisterClass(&wc);  
    // Create the window.  
    HWND hwnd = CreateWindowEx(  
        0,                              // Optional window styles.  
        CLASS_NAME,                     // Window class  
        L"Learn to Program Windows",    // Window text  
        WS_OVERLAPPEDWINDOW,            // Window style  
        // Size and position  
        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,  
        NULL,       // Parent window      
        NULL,       // Menu  
        hInstance,  // Instance handle  
        NULL        // Additional application data  
    );  
    if (hwnd == NULL)  
    {  
        return 0;  
    }  
    ShowWindow(hwnd, nCmdShow);  
    // Run the message loop.  
    MSG msg = { };  
    while (GetMessage(&msg, NULL, 0, 0) > 0)  
    {  
        TranslateMessage(&msg);  
        DispatchMessage(&msg);  
    }  
    return 0;  
}  
  
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)  
{  
    switch (uMsg)  
    {  
    case WM_DESTROY:  
        PostQuitMessage(0);  
        return 0;  
  
    case WM_PAINT:  
    {  
        PAINTSTRUCT ps;  
        HDC hdc = BeginPaint(hwnd, &ps);  
        // All painting occurs here, between BeginPaint and EndPaint.  
        FillRect(hdc, &ps.rcPaint, (HBRUSH)(COLOR_WINDOW + 1));  
        EndPaint(hwnd, &ps);  
    }  
    return 0;  
    }  
    return DefWindowProc(hwnd, uMsg, wParam, lParam);  
}  
int main()  
{  
    return 0;  
}  

Best regards,

Elya

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