Mingw undefined references.

[Blackroot]

I just tried building a windows program in mingw. I built mingw & msys off of auto installing exes.

It doesnt seem to be a library issue per-se. Rather, it seems the library is missing some definitions. I would put this in the C++ board/Windows board, but it seems more a problem with mingw.

C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0x57):rpg.cpp: undefined reference to `DeleteObject@4'
C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0xf0):rpg.cpp: undefined reference to `CreateCompatibleDC@4'
C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0x10a):rpg.cpp: undefined reference to `SelectObject@8'
C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0x12c):rpg.cpp: undefined reference to `GetObjectA@12'
C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0x177):rpg.cpp: undefined reference to `BitBlt@36'
C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0x18c):rpg.cpp: undefined reference to `SelectObject@8'
C:/DOCUME~1/USER1~1/LOCALS~1/Temp/ccmqbaaa.o(.text+0x19a):rpg.cpp: undefined reference to `DeleteDC@4'

It only bugs me about my paint procedures. But, not all of them seem to be bugged. Its a weird issue, it says nothing else. No missing libraries, nothing.

Heres my bugged code for reference:

  case WM_CREATE:
   ScreenDisplay_Object = LoadBitmap(GetModuleHandle(NULL),"C:\\ball.bmp");
   if(ScreenDisplay_Object == NULL)
    MessageBox(hwnd, "Could not load object!", "Error", MB_OK | MB_ICONEXCLAMATION);
   break;

  case WM_PAINT: {
   BITMAP bm;
   PAINTSTRUCT ps;

   HDC hdc = BeginPaint(hwnd, &ps); // 31

   HDC hdcMem = CreateCompatibleDC(hdc);
   HBITMAP hbmOld = (HBITMAP)SelectObject(hdcMem, ScreenDisplay_Object); //34

   GetObject(ScreenDisplay_Object, sizeof(bm), &bm);

   BitBlt(hdc, 0, 0, bm.bmWidth, bm.bmHeight, hdcMem, 0, 0, SRCCOPY);

   SelectObject(hdcMem, hbmOld);
   DeleteDC(hdcMem);
 
   EndPaint(hwnd, &ps);
   }
   break;

  default:
   return DefWindowProc(hwnd, msg, wParam, lParam);
 }

I looked in the mingw wiki / documentation. It didint mention this :/. Anyone have mingw do the same thing to them?

[Ken Fitlike]

Looks like you haven't linked with the gdi32 library (-lgdi32) - exactly what instructions are you using to build your program?

For example, for a single file windows program, test.cpp, you would build it as follows from a command prompt or msys command line:

g++ test.cpp -mwindows -o test.exe

The -mwindows switch is passed to the linker and ensures basic configuration for a windows application including the linking of some common windows libraries such as gdi32, kernel32 and user32.

[Blackroot]

Oh, mingw is so different then borland, always catchs me offguard. Thank you for that ken.