-#ifdef HAVE_STRERROR
- extern char *strerror OF((int));
-# define zstrerror(errnum) strerror(errnum)
-#else
-# define zstrerror(errnum) ""
+#if defined(STDC99) || (defined(__TURBOC__) && __TURBOC__ >= 0x550)
+# ifndef HAVE_VSNPRINTF
+# define HAVE_VSNPRINTF
+# endif
+#endif
+#if defined(__CYGWIN__)
+# ifndef HAVE_VSNPRINTF
+# define HAVE_VSNPRINTF
+# endif
+#endif
+#ifndef HAVE_VSNPRINTF
+# ifdef MSDOS
+ /* vsnprintf may exist on some MS-DOS compilers (DJGPP?),
+ but for now we just assume it doesn't. */
+# define NO_vsnprintf
+# endif
+# ifdef __TURBOC__
+# define NO_vsnprintf
+# endif
+# ifdef WIN32
+ /* In Win32, vsnprintf is available as the "non-ANSI" _vsnprintf. */
+# if !defined(vsnprintf) && !defined(NO_vsnprintf)
+# define vsnprintf _vsnprintf
+# endif
+# endif
+# ifdef __SASC
+# define NO_vsnprintf
+# endif
+#endif
+#ifdef VMS
+# define NO_vsnprintf