D Programming Language 2.0

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Last update Fri Jan 20 13:27:27 2012

# Windows

This describes the D implementation for 32 bit Windows systems. Naturally, Windows specific D features are not portable to other platforms.

Instead of the:

    #include <windows.h>

of C, in D there is:

    import std.c.windows.windows;

## Calling Conventions

In C, the Windows API calling conventions are `__stdcall`. In D, it is simply:

    extern (Windows)
    {
    	/* ... function declarations ... */
    }

The Windows linkage attribute sets both the calling convention and the name mangling scheme to be compatible with Windows.

For functions that in C would be `__declspec(dllimport)` or `__declspec(dllexport)`, use the `export` attribute:

    export void func(int foo);

If no function body is given, it's imported. If a function body is given, it's exported.

## Windows Executables

Windows GUI applications can be written with D. A sample such can be found in `\dmd2\samples\d\winsamp.d`

These are required:

1. Instead of a `main` function serving as the entry point, a `WinMain` function is needed.
2. `WinMain` must follow this form:

       import core.runtime;
       import std.c.windows.windows;
       import std.string;

       extern (Windows)
       int WinMain(HINSTANCE hInstance,
           HINSTANCE hPrevInstance,
           LPSTR lpCmdLine,
           int nCmdShow)
       {
         int result;

         void exceptionHandler(Throwable e) {
           throw e;
         }

         try {
           Runtime.initialize(&exceptionHandler);
           result = myWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
           Runtime.terminate(&exceptionHandler);
         }

         catch (Throwable e) { // catch any uncaught exceptions
           MessageBoxA(null, e.toString().toStringz, "Error",
               MB_OK | MB_ICONEXCLAMATION);
           result = 0;             // failed
         }

         return result;
       }

       int myWinMain(HINSTANCE hInstance,
           HINSTANCE hPrevInstance,
           LPSTR lpCmdLine,
           int nCmdShow)
       {
         // ... insert user code here ...
         return 0;
       }

   The `myWinMain()` function is where the user code goes, the rest of `WinMain` is boilerplate to initialize and shut down the D runtime system.
3. A `.def` (Module Definition File) with at least the following two lines in it:

       EXETYPE NT
       SUBSYSTEM WINDOWS

   Without those, Win32 will open a text console window whenever the application is run.
4. The presence of `WinMain()` is recognized by the compiler causing it to emit a reference to __acrtused_dll and the phobos.lib runtime library.

## Windows Programming Examples

A collection of over 140 Windows D programming code examples is available at this Github repository.
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