Re: Lua 5.1 / 5.2 threads

[Jim Whitehead II <jnwhiteh@...>]

On Wed, Apr 27, 2011 at 5:32 PM, Peter Cawley <lua@corsix.org> wrote:
> On Wed, Apr 27, 2011 at 5:27 PM, Jim Whitehead II <jnwhiteh@gmail.com> wrote:
>> On Wed, Apr 27, 2011 at 4:28 PM, Anthony Howe <achowe+lua@snert.com> wrote:
>>> On 27/04/2011 16:57, Peter Cawley whispered from the shadows...:
>>>> On Wed, Apr 27, 2011 at 3:53 PM, Anthony Howe <achowe+lua@snert.com> wrote:
>>>>> In Lua 5.1 a thread has an environment and section 2.8 starts with
>>>>> "Every value in Lua can have a metatable." So a thread can also have a
>>>>> metatable in addition to an environment?
>>>>
>>>> If you continue reading 2.8, then you find the following:
>>>>
>>>> "Tables and full userdata have individual metatables (although
>>>> multiple tables and userdata can share their metatables). Values of
>>>> all other types share one single metatable per type; that is, there is
>>>> one single metatable for all numbers, one for all strings, etc."
>>>
>>> Yes. I had seen that but didn't think to apply it to a complex type like
>>> a thread.
>>>
>>>> So every thread can have a metatable, but the granularity for setting
>>>> metatables on threads is such that if one thread has a metatable, then
>>>> all threads have that metatable. As far as I'm aware, this hasn't
>>>> changed between 5.1 and 5.2.
>>>
>>> What about the master state (returned by luaL_newstate()) from which a
>>> thread is derived? For the purpose of this question do they have the
>>> same type and status a threads? or are they treated differently?
>>>
>>> So if I change the metatable of a master state then all future
>>> lua_State, master or thread, will share the same metatable?
>>>
>>
>> I'm not sure I understand your question. What would "changing the
>> metatable" of the master state mean? The master state isn't a Lua
>> value, so metatables don't really apply in the same way they do to
>> other values.
>
> The master state can be made into a Lua value by lua_pushthread (or
> coroutine.running() in 5.2). For the purpose of this question, they
> have the same type; a single metatable is shared between everything
> which you can turn into a lua_State*.

Ah thanks, that was the bit I was missing!

- Jim