CODEWITHSUNDEEP
c++cwindowsheaderlinker
Cecil
Cecil

Reputation: 155

Compile on WIN32 without Windows.h

As a learning exercise I've written a standard Windows program that registers and creates a window without explicitly including Windows.h. All header symbols from Windows.h have been extracted and placed into a custom header which I include into the source. The custom header has type definitions like CreateWindow and WNDCLASSEX.

The program is compiled with cl.exe with a command line like so:

cl main.cpp /link opengl32.lib gdi32.lib kernel32.lib user32.lib

It is my understanding that these .lib files are import libs which do setup work for loading in function addresses from the associated DLLs upon process startup. The above command line will work perfectly fine if main.cpp includes Windows.h directly. However, when including the custom header cl.exe fails to link all function calls made into the Windows API, despite having specified the associated import libs on the command line (unresolved external symbol errors).

Is there some kind of special-case magic cl.exe performs specifically for Windows.h? What steps are necessary to ensure proper linking in this scenario?

Here is the smallest example I could construct:

typedef unsigned __int64 UINT_PTR, *PUINT_PTR;
typedef __int64 LONG_PTR, *PLONG_PTR;
typedef UINT_PTR            WPARAM;
typedef LONG_PTR            LPARAM;
typedef LONG_PTR            LRESULT;
typedef int                 INT;
typedef unsigned int        UINT;
typedef char CHAR;
typedef unsigned short      WORD;
#define CONST const
#define DECLARE_HANDLE(name) struct name##__{int unused;}; typedef struct name##__ *name
DECLARE_HANDLE(HWND);
DECLARE_HANDLE(HINSTANCE);
DECLARE_HANDLE(HICON);
DECLARE_HANDLE(HCURSOR);
DECLARE_HANDLE(HBRUSH);
DECLARE_HANDLE(HMODULE);
typedef unsigned __int64 ULONG_PTR, *PULONG_PTR;
typedef CHAR *NPSTR, *LPSTR, *PSTR;
typedef CONST CHAR *LPCSTR, *PCSTR;
#define CALLBACK    __stdcall
#define WINAPI      __stdcall
typedef LRESULT (CALLBACK* WNDPROC)(HWND, UINT, WPARAM, LPARAM);
#define DECLSPEC_IMPORT __declspec(dllimport)
#define WINUSERAPI DECLSPEC_IMPORT
#define WINBASEAPI DECLSPEC_IMPORT
#define CS_VREDRAW          0x0001
#define CS_HREDRAW          0x0002
#define CS_OWNDC            0x0020
#define MAKEINTRESOURCEA(i) ((LPSTR)((ULONG_PTR)((WORD)(i))))
#define MAKEINTRESOURCE  MAKEINTRESOURCEA
#define IDC_ARROW           MAKEINTRESOURCE(32512)
#define NULL 0
typedef WORD                ATOM;   //BUGBUG - might want to remove this from minwin

typedef struct tagWNDCLASSEXA {
    UINT        cbSize;
    /* Win 3.x */
    UINT        style;
    WNDPROC     lpfnWndProc;
    int         cbClsExtra;
    int         cbWndExtra;
    HINSTANCE   hInstance;
    HICON       hIcon;
    HCURSOR     hCursor;
    HBRUSH      hbrBackground;
    LPCSTR      lpszMenuName;
    LPCSTR      lpszClassName;
    /* Win 4.0 */
    HICON       hIconSm;
} WNDCLASSEXA, *PWNDCLASSEXA, *NPWNDCLASSEXA, *LPWNDCLASSEXA;

WINUSERAPI LRESULT CALLBACK DefWindowProcA(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
WINBASEAPI HMODULE WINAPI GetModuleHandleA(LPCSTR lpModuleName);
WINUSERAPI HCURSOR WINAPI LoadCursorA(HINSTANCE hInstance, LPCSTR lpCursorName);
WINUSERAPI ATOM WINAPI RegisterClassExA(CONST WNDCLASSEXA *);

LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam )
{
    return DefWindowProcA( hWnd, message, wParam, lParam );
}

INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE hPrev, LPSTR szCmdLine, INT sw )
{
    // register window class
    WNDCLASSEXA wcex = { 0 };
    wcex.cbSize            = sizeof( WNDCLASSEXA );
    wcex.style            = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
    wcex.lpfnWndProc    = WndProc;
    wcex.hInstance        = (HINSTANCE)GetModuleHandleA( NULL );
    wcex.hIcon            = NULL;
    wcex.hCursor        = LoadCursorA( NULL, IDC_ARROW );
    wcex.lpszClassName    = "Title";
    RegisterClassExA( &wcex );

    return 0;
}

Compiled with:

@echo off
call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" x64

set CONSOLE= -subsystem:windows
set CFLAGS= -Zi -nologo
set CFLAGS= -D__WINDOWS__ -D_CRT_SECURE_NO_WARNINGS %CFLAGS%
set LFLAGS= -incremental:no -opt:ref
set LFLAGS= user32.lib kernel32.lib %LFLAGS%

cl %CFLAGS% main.cpp -Fegame.exe /link %LFLAGS% %CONSOLE%

Upvotes: 2

Views: 2858

Answers (1)

Jerry Coffin
Jerry Coffin

Reputation: 490408

No, the tools don't do anything especially for windows.h.

I'd guess you've gotten your header wrong. It's hard to guess what the problem might be without seeing the header, but one possibility sticks out.

For most functions, Windows has both "ANSI" and "Wide" versions, so what you see as CreateWindow is really two functions CreateWindowA and CreateWindowW. CreateWindow exists only as a macro that maps to either the *A or *W name, depending upon whether UNICODE is defined.

So, if you've provided a prototype/declaration for a function named CreateWindow, it's not going to link--what exists in the library are CreateWindowA and CreateWindowW, not CreateWindow.

Upvotes: 4

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