Added check routine for gw_buffer. Only effective in debug build.

utils/skygw_debug.h

@@ -16,7 +16,7 @@
  * Copyright SkySQL Ab 2013
  */
 
-
+#include <stdio.h>
 #include <assert.h>
 
 #define __USE_UNIX98 1 
@@ -360,6 +360,11 @@ typedef enum skygw_chk_t {
                             "Session under- or overflow");              \
     }
 
+#define CHK_GWBUF(b) {                                                  \
+            ss_info_dassert(((b)->start <= (b)->end),                   \
+                            "gwbuf start has passed the endpoint");     \
+    }
+
 #if defined(SS_DEBUG)
 bool conn_open[1024];
 #endif