some fixes for systems without va_copy

asprintf.c

@@ -1,34 +1,49 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include "asprintf.h"
 
-#ifndef va_copy
+/* some implementations have __va_copy instead of va_copy */
+#if !defined(va_copy) && defined (__va_copy)
 #define va_copy __va_copy
 #endif
 
 int vasprintf(char** pbuffer, const char* format, va_list ap)
 {
+    int len = -1;
+
+#ifdef va_copy
     va_list ap2;
-    int len;
+    va_copy(ap2, ap);
+#else
+    /* if we have no va_copy, we probably don't need one */
+    #define ap2 ap
+#endif
 
 #if defined(vxWorks)
-    FILE* f;
-    /* print to null device to get required buffer length */
-    if ((f = fopen("/null","w")) != NULL)
     {
-        len = vfprintf(f, format, ap2);
-        fclose(f);
+        FILE* f;
+        /* print to null device to get required buffer length */
+        if ((f = fopen("/null","w")) != NULL)
+        {
+            len = vfprintf(f, format, ap2);
+            fclose(f);
+        }
     }
 #elif defined(_WIN32)
-    len = _vscprintf(format, ap);
+    len = _vscprintf(format, ap2);
 #else
-    len = vsnprintf(NULL, 0, format, ap);
+    len = vsnprintf(NULL, 0, format, ap2);
 #endif
+
+#ifdef va_copy
     va_end(ap2);
+#endif
+    
     if (len <= 0)
     {
-        fprintf(stderr, "vasprintf: too old version on vsnprintf\n");
-        return len;
+        fprintf(stderr, "vasprintf: error calculating needed size\n");
+        return -1;
     }
     *pbuffer = malloc(len+1);
     if (*pbuffer == NULL) return -1;