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----- Reply message -----
From: "Brian Maher" <brian@brimworks.com>
To: "Lua mailing list" <lua-l@lists.lua.org>
Subject: A Question of Style
Date: Wed, Dec 7, 2011 10:12 pm


The specific case where yield doesn't work is if yield needs to "save"
the C stack frame (lua function calls C function which calls lua
function that calls yields).  The lua_yield function (as mentioned in
the documentation) must be the last statement of your C function since
it won't preserve the C stack.  There is more about this limitation
here (including how to overcome it):

  http://coco.luajit.org/

Cheers,
-Brian

On Wed, Dec 7, 2011 at 9:07 AM, Enrico Colombini <erix@erix.it> wrote:
> On 07/12/2011 17.52, Sam Roberts wrote:
>>
>> You can't yield across a C call boundary. Not without luajit or coco.
>
>
> This is allowed (and works):
>
> -------------------------------------
> static int
> LuaWaitImageReady(lua_State *lua)
> {
>    int tid = luaL_checkint(lua, 1);
>    bool waitFinished = (lua_toboolean(lua, 2) != 0);
>
>    if (Gale->WaitImageReady(tid, waitFinished))
>    {
>        //ready: return normally
>        return 0;
>    }
>    else
>    {
>        //not ready: suspend coroutine  ---  yield from C side ---
>        return lua_yield(lua, 0);
>    }
> } //LuaWaitImageReady
> -------------------------------------
>
> The above function is called from a Lua coroutine.
>
> --
>  Enrico
>



-- 
Brian Maher >> Glory to God <<