C语言 如何在lua中检查用户数据
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How to inspect userdata in lua
提问by u443966
I am using inspect.luato inspect table to string.
我正在使用inspect.lua来检查表到字符串。
But, if the value is a userdata, it returns just <userdata 1>
但是，如果值是一个用户数据，它只返回 <userdata 1>
I really need to know what the userdata type is, what the userdata value is, it's very important for debuging, I don't want do it in any IDE, I just want something can help me debug by print staffs.
我真的需要知道 userdata 类型是什么，userdata 值是什么，这对调试非常重要，我不想在任何 IDE 中进行，我只是希望打印人员可以帮助我调试。
回答by fouronnes
You cannot.
你不能。
From the manual:
从手册：
The type userdata is provided to allow arbitrary C data to be stored in Lua variables. A userdata value is a pointer to a block of raw memory. [...] Userdata has no predefined operations in Lua, except assignment and identity test.
提供 userdata 类型以允许将任意 C 数据存储在 Lua 变量中。用户数据值是指向原始内存块的指针。[...] Userdata 在 Lua 中没有预定义的操作，除了赋值和身份测试。
As indicated by @Eric, the only thing you can do from Lua is inspect the metatable :
正如@Eric 所指出的，你可以从 Lua 做的唯一一件事就是检查元表：
print(inspect(getmetatable(someuserdata)))
If you are using the C API, you should be able to register a custom function that prints whatever is held by the block.
如果您使用的是 C API，您应该能够注册一个自定义函数来打印块所持有的任何内容。
回答by Oliver
If the userdata metatable was created with luaL_newmetatableit contains an entry __namecontaining the userdatas type (since Lua version 5.3), see https://www.lua.org/manual/5.3/manual.html#luaL_newmetatable. Unfortunately this feature is still not widely used.
如果创建的 userdata 元表luaL_newmetatable包含一个__name包含 userdatas 类型的条目（自 Lua 5.3 版起），请参阅https://www.lua.org/manual/5.3/manual.html#luaL_newmetatable。不幸的是，这个功能仍然没有被广泛使用。
