error: request for member 'length' in 'buffers', which is of non-class type 'buffer*'

代码：
buffers = calloc (req.count, sizeof (*buffers));

错误：
error: request for member 'length' in 'buffers', which is of non-class type 'buffer*'

原因：
大多数编译器，要求malloc时必须强制类型转换

修改后：
buffers = (struct buffer*)calloc (req.count, sizeof (*buffers));