Add #ifdefs around forwards and interfaces like MIDL does.

include/unknwn.h

@@ -15,12 +15,19 @@ extern "C" {
 # define ICOM_MSVTABLE_COMPAT_FIELDS
 # define ICOM_MSVTABLE_COMPAT_DummyRTTIVALUE
 #endif
+#ifndef __IUnknown_FWD_DEFINED__
+#define __IUnknown_FWD_DEFINED__
 typedef struct IUnknown IUnknown;
+#endif
+
 typedef IUnknown *LPUNKNOWN;
 
 /*****************************************************************************
  * IUnknown interface
  */
+#ifndef __IUnknown_INTERFACE_DEFINED__
+#define __IUnknown_INTERFACE_DEFINED__
+
 DEFINE_GUID(IID_IUnknown, 0x00000000, 0x0000, 0x0000, 0xc0,0x00, 0x00,0x00,0x00,0x00,0x00,0x46);
 #if defined(__cplusplus) && !defined(CINTERFACE)
 #ifdef ICOM_USE_COM_INTERFACE_ATTRIBUTE
@@ -100,12 +107,21 @@ void __RPC_STUB IUnknown_Release_Stub(
     PRPC_MESSAGE pRpcMessage,
     DWORD* pdwStubPhase);
 
+#endif  /* __IUnknown_INTERFACE_DEFINED__ */
+
+#ifndef __IClassFactory_FWD_DEFINED__
+#define __IClassFactory_FWD_DEFINED__
 typedef struct IClassFactory IClassFactory;
+#endif
+
 typedef IClassFactory *LPCLASSFACTORY;
 
 /*****************************************************************************
  * IClassFactory interface
  */
+#ifndef __IClassFactory_INTERFACE_DEFINED__
+#define __IClassFactory_INTERFACE_DEFINED__
+
 DEFINE_GUID(IID_IClassFactory, 0x00000001, 0x0000, 0x0000, 0xc0,0x00, 0x00,0x00,0x00,0x00,0x00,0x46);
 #if defined(__cplusplus) && !defined(CINTERFACE)
 struct IClassFactory : public IUnknown
@@ -205,6 +221,8 @@ HRESULT __RPC_STUB IClassFactory_LockServer_Stub(
     IClassFactory* This,
     BOOL fLock);
 
+#endif  /* __IClassFactory_INTERFACE_DEFINED__ */
+
 #ifdef __cplusplus
 }
 #endif

tools/widl/header.c

@@ -660,7 +660,10 @@ void write_forward(type_t *iface)
    * (i.e. this is an IDL forward), then we also assume that it is an object
    * interface, since non-object interfaces shouldn't need forwards */
   if ((!iface->defined || is_object(iface->attrs)) && !iface->written) {
+    fprintf(header,"#ifndef __%s_FWD_DEFINED__\n", iface->name);
+    fprintf(header,"#define __%s_FWD_DEFINED__\n", iface->name);
     fprintf(header, "typedef struct %s %s;\n", iface->name, iface->name);
+    fprintf(header, "#endif\n\n" );
     iface->written = TRUE;
   }
 }
@@ -684,6 +687,8 @@ void write_com_interface(type_t *iface)
   fprintf(header, "/*****************************************************************************\n");
   fprintf(header, " * %s interface\n", iface->name);
   fprintf(header, " */\n");
+  fprintf(header,"#ifndef __%s_INTERFACE_DEFINED__\n", iface->name);
+  fprintf(header,"#define __%s_INTERFACE_DEFINED__\n\n", iface->name);
   write_guid(iface);
   write_forward(iface);
   /* C++ interface */
@@ -732,6 +737,7 @@ void write_com_interface(type_t *iface)
 
   if (!is_local(iface->attrs))
     write_proxy(iface);
+  fprintf(header,"#endif  /* __%s_INTERFACE_DEFINED__ */\n\n", iface->name);
 }
 
 void write_rpc_interface(type_t *iface)