Re: Technical question wrt lua_pcall() and errors

[Drake Wilson <drake@...>]

Quoth Marc Balmer <marc@msys.ch>, on 2011-01-18 11:48:31 +0100:
> > A pcall doesn't by itself modify any I/O streams or the process
> > environment.  Could you show more context regarding where the
> > lua_pcall happens?  In particular, where are you getting the Lua
> > state, and what do you do with the Lua stack before and after the
> > pcall?  Does this still happen if you replace the Lua code with
> > trivial Lua code that does nothing except throw an error?
> 
> The code that causes the error is a trivial example (indexing a nil
> value),

As in just « return nil['foo'] », say, or doing that after some other
work?

> the Lua state is created in fcgi_handler, then pcall(), then
> send a CGI response back to the server.  What would also disrupt the
> communiction beetween my app and the webserver was any output the
> pcall() is causing.  But I doubt Lua does output anything on it's own,
> or am I wrong?

Normally it does not.  What do you do with the Lua universe afterwards
in fcgi_handler?  Destroy it again?  What happens if you replace the
fcgi_handler() with a complete no-op (that is, FCGI_Accept, then
FCGI_Finish immediately)?

I'm imagining the Lua program outputting a half-finished FCGI response
or none at all and then dying and FCGI_Finish not cleaning everything
up completely.  I don't recall how stock C FCGI works very well.

   ---> Drake Wilson