The thread:alive() method may not work

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Depending on the pthread implementation, the thread:alive() method may not work.

Existing implementations vary on the result of a pthread_kill() with a thread ID indicating an inactive thread (a terminated thread that has not been detached or joined). Some indicate success on such a call, while others give an error of [ESRCH].

The glibc seems to return success since 2.34

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Could be reproduced with the following code.

local llthreadsLib = require('llthreads')
local luaSocketLib = require('socket')

local t = llthreadsLib.new([[
    luaSocketLib = require('socket')
    luaSocketLib.sleep(1)
    print('ended')
]])
t:start(false, true)

for i = 1, 5 do
    print('alive', t:alive())
    luaSocketLib.sleep(0.5)
end

print('join', t:join())

Which results in

lua work/llthread.lua 
alive   true
alive   true
ended
alive   true
alive   true
alive   true
join    true