Index: /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3kit.h
===================================================================
--- /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3kit.h	(revision 66110)
+++ /trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3kit.h	(revision 66111)
@@ -38,4 +38,19 @@
 #endif
 
+
+/*
+ * Work around ms_abi trouble in the gcc camp (gcc bugzilla #50818).
+ * ASSUMES all va_lists are in functions with
+ */
+#if defined(__GNUC__) && ARCH_BITS == 64
+# undef  va_list
+# undef  va_start
+# undef  va_end
+# undef  va_copy
+# define va_list                    __builtin_ms_va_list
+# define va_start(a_Va, a_Arg)      __builtin_ms_va_start(a_Va, a_Arg)
+# define va_end(a_Va)               __builtin_ms_va_end(a_Va)
+# define va_copy(a_DstVa, a_SrcVa)  __builtin_ms_va_copy(a_DstVa, a_SrcVa)
+#endif