LR Exception ACCESS_VIOLATION received

出错场景;

char * cookie;

  sprintf(cookie, "%8d%8d", 123, 4567); //产生：" 123 4567"
  lr_output_message("vaule of %s",cookie);

运行后提示：

Action.c(119): Error: C interpreter run time error: Action.c (119):  Error -- memory violation : Exception ACCESS_VIOLATION received.

将

char * cookie; 改为 char  cookie[100]; 再运行一切ok

怎样防止呢？？难道就这一种办法了吗？