diff -ur zlib-1.1.4/configure zlib-1.1.4-vsnprintf/configure
--- zlib-1.1.4/configure	Wed Jul  8 13:19:35 1998
+++ zlib-1.1.4-vsnprintf/configure	Mon Feb 24 00:06:55 2003
@@ -167,6 +167,54 @@
 fi
 
 cat > $test.c <<EOF
+#include <stdio.h>
+#include "zconf.h"
+
+#ifdef STDC
+
+#include <stdarg.h> 
+
+int test (const char *format, /* args */ ...)
+{
+  char buf[10];
+  va_list va;
+  int len;
+
+  va_start(va, format);
+  len = vsnprintf(buf, sizeof(buf), format, va);
+  va_end(va);
+
+  return len;
+}
+
+#else /* not ANSI C */
+
+int test(format, a1, a2)
+  const char *format;
+  int a1, a2;
+{
+  char buf[10];
+  int len;
+
+  len = snprintf(buf, sizeof(buf), format, a1, a2);
+
+  return len;
+}
+#endif
+
+int main(void)
+{
+  exit(0);
+}
+EOF
+if test "`($CC -c $CFLAGS $test.c) 2>&1`" = ""; then
+  CFLAGS="$CFLAGS -DHAS_vsnprintf -DHAS_snprintf"
+  echo Checking for [v]snprintf support... Yes.
+else
+  echo Checking for [v]snprintf support... No.
+fi
+
+cat > $test.c <<EOF
 #include <sys/types.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
diff -ur zlib-1.1.4/gzio.c zlib-1.1.4-vsnprintf/gzio.c
--- zlib-1.1.4/gzio.c	Mon Mar 11 08:16:01 2002
+++ zlib-1.1.4-vsnprintf/gzio.c	Mon Feb 24 07:48:36 2003
@@ -530,13 +530,12 @@
 
     va_start(va, format);
 #ifdef HAS_vsnprintf
-    (void)vsnprintf(buf, sizeof(buf), format, va);
+    len = vsnprintf(buf, sizeof(buf), format, va);
 #else
-    (void)vsprintf(buf, format, va);
+    len = vsprintf(buf, format, va);
 #endif
     va_end(va);
-    len = strlen(buf); /* some *sprintf don't return the nb of bytes written */
-    if (len <= 0) return 0;
+    if ((len <= 0) || (len >= Z_PRINTF_BUFSIZE)) return 0;
 
     return gzwrite(file, buf, (unsigned)len);
 }
@@ -553,14 +552,13 @@
     int len;
 
 #ifdef HAS_snprintf
-    snprintf(buf, sizeof(buf), format, a1, a2, a3, a4, a5, a6, a7, a8,
+    len = snprintf(buf, sizeof(buf), format, a1, a2, a3, a4, a5, a6, a7, a8,
 	     a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20);
 #else
-    sprintf(buf, format, a1, a2, a3, a4, a5, a6, a7, a8,
+    len = sprintf(buf, format, a1, a2, a3, a4, a5, a6, a7, a8,
 	    a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20);
 #endif
-    len = strlen(buf); /* old sprintf doesn't return the nb of bytes written */
-    if (len <= 0) return 0;
+    if ((len <= 0) || (len >= Z_PRINTF_BUFSIZE)) return 0;
 
     return gzwrite(file, buf, len);
 }