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Re: [Enigma-devel] ant33.lua runtime error under lua 5

From: Tacvek
Subject: Re: [Enigma-devel] ant33.lua runtime error under lua 5
Date: Mon, 19 Jun 2006 15:17:10 -0400

----- Original Message ----- From: "Andreas Lochmann" <address@hidden>
To: "Tacvek" <address@hidden>
Cc: <address@hidden>
Sent: Monday, June 19, 2006 6:36 AM
Subject: Re: [Enigma-devel] ant33.lua runtime error under lua 5

Tacvek wrote:

Some sort of runtime error occurs in ant33.lua ("Unfair!"). This happens when the player fist steps on the trigger. The error message is cut short because it does not wrap, so I cannot debug at this time. Can somebody take a look at it?

The full error-message is:
 Server Error: level runtime error
 callback 'action_A' failed:
 .../ant.lua:141: attempt to compare userdata with number
(and, yes, it is annoying that error-messages don't wrap
in lower resolutions)

This looks like a type-cast-problem in ant.lua, and appears
a second time on the 'action_C'-triggers in ant33.
I don't understand the ant.lua-magic, so I only could do a
workaround for ant33 - a not beautiful one. And we should
assume that there are more levels using this very special

Actually, I'm betting we failed to convert ant.lua over to 5.1 quite correctly.

My guess:
It has to do with how upvalues in functions were resolved at function construction time in Lua 4, while in lua 5.0+ if just the variable name is used, it is resolved when the function is run. Take a look at line 361 of ant.lua. Here an anonymous function is created and returned. This happens each time the cell function is run. Previously, any upvalues would be resolved while running the cell function. Now any such values are only resolved when the function returned by cell is run.

There is a workaround, described in http://lua-users.org/lists/lua-l/2005-11/msg00314.html .

However, perhaps that is not the cause, because the error message claims the error occurs elsewhere. I can't see where any of the relevent tables could be picking up userdata. Besides, using the above fix, but deep copying the tables does not seem to fix the problem.

A lua expert really needs to look at this.

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