+/* C99 defines va_copy() for copying a varargs ap so that it can be reused,
+since on some platforms multiple iterations of va_start()/va_end() are not
+supported. But va_copy() is itself not so portable. Hack around it.
+See portability notes at: http://unixpapa.com/incnote/variadic.html */
+
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+/* va_copy exists for us or the system is broken and we need OS hacks */
+#elif defined(va_copy)
+/* trust it; hope that va_copy is always a macro when defined */
+#elif !defined(va_copy) && defined(__va_copy)
+#define va_copy(dest, src) __va_copy(dest, src)
+#else
+#define va_copy(dest, src) do { memcpy(dest, src, sizeof(va_list) } while (0)
+#endif
+