Re: problem with lua_newthread, setfenv and modules

["Peter Cawley" <lua@...>]

Have you tried:
lfs = require "lfs"

Also, the Lua manual states:
" The thread environment (where global variables live) is always at
pseudo-index LUA_GLOBALSINDEX. The environment of the running C
function is always at pseudo-index LUA_ENVIRONINDEX."
Hence, setting a thread environment is the same as setting the thread
globals index. My guess is that LFS loaded its global table using the
globals index, so while the require function's environment index is
the globals table for the master state, because require was called
from a thead, using the globals index gives you the globals for that
thread, whereas if LFS loaded into the environment index, it would
load into (in this case) the master state globals.

My 2 cents.

2008/5/13 Graham Wakefield <lists@grahamwakefield.net>:
> Hi,
>
>  I have an application in which lua scripts may be loaded by the user. Each
> script is given a 'child' lua_State created by lua_newthread(). Keeping each
> table's variables separate is beneficial to the application, so the child
> state is given a local environment, with a metatable __index to the master
> globals, like this:
>
>                 lua_State *Ls = lua_newthread(L);
>
>                 // Create a local environment with a link to global
> environment via __index metamethod
>                 // this means that script variables are not shared between
> scripts
>                 lua_pushthread(Ls);
>                         lua_newtable( Ls );
>                                 lua_pushvalue( Ls, -1 );
>                                 lua_setmetatable( Ls, -2 ); //Set itself as
> metatable
>                                 lua_pushvalue( Ls, LUA_GLOBALSINDEX );
>                                 lua_setfield( Ls, -2, "__index" );
>                         lua_setfenv( Ls, -2 );
>                 lua_pop(Ls, 1);
>
>  A user script can load a module using require (e.g. require "lfs"), which
> works as normal. However, if a second script is loaded, the global 'lfs' is
> not accessible to the second script.
>
>  script 1:
>
>  require "lfs"
>  print(lfs) -- table (0x....)
>
>  script 2:
>
>  require "lfs"
>  print(lfs) -- nil
>  print(package.loaded.lfs) -- table (0x...)
>
>  I can't quite figure out why the second script doesn't get global access to
> the module. I wonder if the require() call is pushing the module as a global
> into script 1's environment, rather than the master state. Is this the case?
> [in fact, does lua_setfenv() on a lua_State do the same as lua_replace(Ls,
> LUA_GLOBALSINDEX)?]
>
>  Is there a known workaround?
>
>  Thanks,
>
>  Graham
>