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 core.sys.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 \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 core.sys.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.