Re: A tricky way to determine Lua version

[Egor Skriptunoff <egor.skriptunoff@...>]

On Fri, Jun 29, 2018 at 1:32 PM, Thijs Schreijer wrote:

>> --[=[
>> local version = 'Lua 5.0'
>> --[[]=]
>> local n = '8'; repeat n = n*n until n == n*n
>> local t = {'Lua 5.1', nil,
>>  [-1/0] = 'Lua 5.2',
>>  [1/0]  = 'Lua 5.3',
>>  [2]    = 'LuaJIT'}
>> local version = t[2] or t[#'\z'] or t[n/'-0'] or 'Lua 5.4'
>> --]]

It also misses detection of LuaJIT’s 5.2 compatibility flag

The main idea of this "version detector" is to be undeceivable by sandboxing.

A sandboxing environment could change any globals, so this script doesn't rely on globals and libraries.

I don't know how to check for LuaJIT 5.2 compatibility in the same robust way.

I can suggest the following script which depends on "loadstring" global variable:

if version == 'LuaJIT' then
   version = version..(loadstring'b=0b0' and ' 2.1' or ' 2.0')
   version = version..(loadstring';' and ' with LUA52COMPAT' or '')
end