diff --git a/src/tool/omniidl/cxx/cccp/cccp.c b/src/tool/omniidl/cxx/cccp/cccp.c
index 507c330..5651b3e 100644
--- a/src/tool/omniidl/cxx/cccp/cccp.c
+++ b/src/tool/omniidl/cxx/cccp/cccp.c
@@ -182,15 +182,20 @@ my_bzero (b, length)
 # endif
 #endif
 
+#if defined(_MSC_VER)
+#define OMNI_HAVE_VPRINTF
+#define __STDC__
+#endif
+
 #if defined (__STDC__) && defined (OMNI_HAVE_VPRINTF)
 # include <stdarg.h>
 # define VA_START(va_list, var) va_start (va_list, var)
 # define PRINTF_ALIST(msg) char *msg, ...
 # define PRINTF_DCL(msg)
 # define PRINTF_PROTO(ARGS, m, n) PROTO (ARGS) __attribute__ ((format (__printf__, m, n)))
 #else
 # include <varargs.h>
 # define VA_START(va_list, var) va_start (va_list)
 # define PRINTF_ALIST(msg) msg, va_alist
 # define PRINTF_DCL(msg) char *msg; va_dcl
 # define PRINTF_PROTO(ARGS, m, n) () __attribute__ ((format (__printf__, m, n)))
diff --git a/src/tool/omniidl/cxx/cccp/cexp.c b/src/tool/omniidl/cxx/cccp/cexp.c
index 4b4679c..b534fb3 100644
--- a/src/tool/omniidl/cxx/cccp/cexp.c
+++ b/src/tool/omniidl/cxx/cccp/cexp.c
@@ -152,15 +152,20 @@ struct arglist {
 # endif
 #endif
 
+#if defined(_MSC_VER)
+#define OMNI_HAVE_VPRINTF
+#define __STDC__
+#endif
+
 #if defined (__STDC__) && defined (OMNI_HAVE_VPRINTF)
 # include <stdarg.h>
 # define VA_START(va_list, var) va_start (va_list, var)
 # define PRINTF_ALIST(msg) char *msg, ...
 # define PRINTF_DCL(msg)
 # define PRINTF_PROTO(ARGS, m, n) PROTO (ARGS) __attribute__ ((format (__printf__, m, n)))
 #else
 # include <varargs.h>
 # define VA_START(va_list, var) va_start (va_list)
 # define PRINTF_ALIST(msg) msg, va_alist
 # define PRINTF_DCL(msg) char *msg; va_dcl
 # define PRINTF_PROTO(ARGS, m, n) () __attribute__ ((format (__printf__, m, n)))
diff --git a/src/tool/omniidl/cxx/cccp/cexp.y.source b/src/tool/omniidl/cxx/cccp/cexp.y.source
index 6fc69f5..6f59873 100644
--- a/src/tool/omniidl/cxx/cccp/cexp.y.source
+++ b/src/tool/omniidl/cxx/cccp/cexp.y.source
@@ -111,15 +111,20 @@ struct arglist {
 # endif
 #endif
 
+#if defined(_MSC_VER)
+#define OMNI_HAVE_VPRINTF
+#define __STDC__
+#endif
+
-#if defined (__STDC__) && defined (HAVE_VPRINTF)
+#if defined (__STDC__) && defined (OMNI_HAVE_VPRINTF)
 # include <stdarg.h>
 # define VA_START(va_list, var) va_start (va_list, var)
 # define PRINTF_ALIST(msg) char *msg, ...
 # define PRINTF_DCL(msg)
 # define PRINTF_PROTO(ARGS, m, n) PROTO (ARGS) __attribute__ ((format (__printf__, m, n)))
 #else
 # include <varargs.h>
 # define VA_START(va_list, var) va_start (va_list)
 # define PRINTF_ALIST(msg) msg, va_alist
 # define PRINTF_DCL(msg) char *msg; va_dcl
 # define PRINTF_PROTO(ARGS, m, n) () __attribute__ ((format (__printf__, m, n)))