CODEWITHSUNDEEP
c++winapig++
Ash Fire
Ash Fire

Reputation: 37

(C++) Win32 API sample code returning "undefined reference to `WinMain@16'" using g++

I am using the G++ compiler with notepad++.

I am following a tutorial by windows, the code that I am using is the example code from the windows tutorial (https://learn.microsoft.com/en-us/windows/win32/learnwin32/your-first-windows-program) I pasted this into my notepad and attempted to compile it, but I was greeted with an error message.

Here is the code and the message:

#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, 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))
    {
        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);



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

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

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

This is the command I used to compile (powershell)

PS  g++ main.cpp

And this is the message I get when trying to compile (powershell)

c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../libmingw32.a(main.o):(.text.startup+0xa0): undefined reference to `WinMain@16' collect2.exe: error: ld returned 1 exit status

if I try renaming wWinMain to WinMain it gives the error

main.cpp:9:12: error: conflicting declaration of C function 'int WinMain(HINSTANCE, HINSTANCE, PWSTR, int)' int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE, PWSTR pCmdLine, int nCmdShow)
In file included from c:\mingw\include\windows.h:44:0, from main.cpp:5: c:\mingw\include\winbase.h:1263:14: note: previous declaration 'int WinMain(HINSTANCE, HINSTANCE, LPSTR, int)' int APIENTRY WinMain (HINSTANCE, HINSTANCE, LPSTR, int);

and if I try to use the command g++ main.cpp -municode then I get the message

g++.exe: error: unrecognized command line option '-municode'

Upvotes: 2

Views: 1331

Answers (1)

Ash Fire
Ash Fire

Reputation: 37

in the line

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR pCmdLine, int nCmdShow)

I changed wWinMain to WinMain and I changed PWSTR to LPSTR and now it works. I have no clue why. Hope it helps anyone with the same problem (-:

Upvotes: 1

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