Several write tag memory leak issues

[liuchenn]

In mqtt_handle.c, several variables have already been assigned NULL before the neu_json_decode_write_free call.

In rw_handle.c, when the handle_write function calls neu_plugin_op to send data to the southbound device, the neu_msg_new function performs a deep copy of cmd. Regardless of the return result of neu_plugin_op, neu_req_write_tag_fini should be called to free memory, right?

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This issue was automatically translated from Chinese.

[hxy7yx]

There is no bug in the code.

1. Ownership Transfer: Setting pointers to NULL is intentional design.
2. Note that the contents of cmd copied by memcpy are pointers

[liuchenn]

1.所有权转移后继续调用了neu_json_decode_write_free释放了req，此时释放的为NULL
2.是请求的cmd 无论该请求成功与否都需要释放

[hxy7yx]

You still don't understand the ownership management. There is only one logical owner of the memory at any time, and the cleanup is guaranteed regardless of success/failure.

[liuchenn]

是我没注意send和recv 交互的数据是指针类型，这块代码没有内存泄漏