Re: Why is my thread not resuming? (very simple code inside)

["John Klimek" <jklimek@...>]

That fixed my problem!  I don't believe I didn't see that...

After checking the stack, the error message was there (attempt to
concatenate a nil value).

Is it safe to create several (hundreds?) of threads and yield/resume
each of them independantly?

On 8/9/07, Bogdan Harjoc <harjoc@fokus.fraunhofer.de> wrote:
> John Klimek wrote:
> > Here's what I'm doing:
> >
> > // ********
> > // startup.lua  (my script)
> > // ********
> > io.write("startup: before\n");
> > io.write("startup: " .. AskQuestion() .. "\n");
> > io.write("startup: after\n");
> >
>
> io.write("startup: " .. nil .. "\n")
>
> This yields an error when I try to run it: "attempt to concatenate a nil
> value".
>
> > // ********
> > // Delphi Code
> > // ********
> >
> > // My "C" Function
> > function AskQuestion(L : Lua_State) : integer; cdecl;
> > begin
> >   result := lua_yield(L, 0);
> > end;
> >
> > // Register the c-function
> > lua_register(L, 'AskQuestion', AskQuestion);
> >
> > // Create a new thread, load a file into it, and then resume (eg. start it)
> > l_thread := lua_newthread(L);
> > lual_loadfile(l_thread, 'startup.lua'); // returns 0
> > lua_resume(l_thread, 0); // returns 0
>
> I don't think this lua_resume() should return 0. According to the manual
> for
> v5.1, 0 is returned when your coroutine finishes.
>
> > At this point the script begins executing and prints "startup:
> > before".  The script hits the coroutine.yield() and execution is back
> > inside my Delphi program.
> >
> > If I try to resume the coroutine:   lua_resume(l_thread, 0);    it
> > returns "1" and does not do anything.  The script does not continue.
>
> Your AskQuestion() routine should probably return -- from the yield() --
> with a
> string value .. or in any case, not nil. And with lua_resume(L, 0) you are
> returning nil.
>
> That is perhaps why the second lua_resume() returns 1 -- an error code.
> Since
> you will be modifying your script, you might find it useful to say
> something like:
>
> ret = lua_resume(L, ...);
> if (ret && ret != LUA_YIELD)
>        printf("error: %s\n", lua_tostring(L, -1));
>
> > What am I doing wrong?
> >
> > Also, are coroutines just the name for a Lua "thread"?  This is very
> > confusing because they seem to be two different things but I don't
> > know...
> >
>
> Hope I'm not completely missing something.
>
> Cheers!
> Bogdan
>