OnChatMessage and Decal 1.1
Problem: AC crashes to desktop when running the following:
 | Decal 1.1 |
| Updated memlocs.xml (version 1.0.27.0) |
| Certain plugins (including Spam Spanker, Text Hack, hooker, and others) |
Background: the memlocs.xml file contains a number of hex addresses -- basically these addresses are file offsets that define where decal hooks into the relevant functions. Since these offsets change from patch to patch, putting them into an external file relieves the community from having to recompile decal for each monthly patch.
November: the offsets have changed, as usual. Hiting "update" from DenAgent updates the 3 main xml files from the server, one of which is the memlocs.xml file. This you MUST do, regardless of what version of decal that you are running. As of today. the latest memlocs.xml revision is 1.0.27.0.
The Problem: The OnChatMessage function throws an error in some (but not all) clients. It is believed the errors are a result of some type of client optimization, but the exact nature is still unknown. This error is isolated to Decal 1.1 and the aforementioned 1.0.27.0 memlocs.xml file which contains the tag
<memloc name="OnChatMessage" value="004C9ADA"
/>. The error is NOT present when using Decal 2.0 RC1. The error, which causes the AC client to crash, is generated when Decal calls the OnChatMessage function for the first time (The OnChatMessage function is used to intercept a command typed in the chat bar prior to forwarding to the server. Plugins like Spam Spanker, Text Hack, hooker, and others make extensive use of this function).
The Wrong Solution: Someone using a back rev of the memlocs.xml file (which has the OLD value 004E91E5 for OnChatMessage) discovered that decal was not crashing on him, and proclaimed this to be the solution, and recommended that everyone change the value of the OnChatMessage memloc to the old value of 004E91E5.
Why This is Wrong: This really doesn't fix anything - in reality, using this solution causes Decal to attempt to call the OnChatMessage function by hooking was basically amounts to a random memory location. Of course OnChatMessage does NOT work with this 'solution' ... but an extremely fortunate coincidence of using this memory location is that calling it happens NOT to crash anything.
A better fix: The new memory location IS correct -- i.e. it IS the proper entry point into OnChatMessage. The fact that it works beautifully with Decal 2.0 is testament to that. Why it does not work with SOME Decal 1.1 clients is still unsolved. IF your client is one that crashes, the proper solution is to DISABLE the use of OnChatMessage, NOT send it off into never-never land (WHY? think of when the client changes again. It will DEFINITELY change next patch, and I'm betting it will change before then to correct things like the subsequent login crash bug. And the results of the 'random' call could be a whole lot worse).
How to do the better fix: Easy. Remove the OnChatMessage tag from the memlocs.xml file -- this means removing the whole line that looks like:
<memloc name="OnChatMessage" value="00xxxxx"
/>
You can use any text editor that you like to edit the memlocs file ... notepad work wonderfully for this task.
