[Sourcemm-coding] Cvar Warning

[David A. <dv...@wp...>]

Hello everyone/anyone (first email?!)

Currently, if you hot-unload SourceMM plugins which have any type of 
ConCommandBase (cvar, concmd), it will crash.

This is because the HL2 engine does not provide a way to unregister 
cvars/concmds. Rather than provide a way, Valve has done some weird 
things. For example, you can't actually unload server plugins from 
memory (plugin_unload does not free them), because the HL2 engine is 
still relying on their cvars.

However, Metamod:Source frees plugins properly so you can write over the 
file and keep testing. This means, if you use "meta unload", the HL2 
engine will keep trying to access your cvars/concmds and promptly crash. 
The server might also crash on exit.

How do you prevent this? The next release of SourceMM will expand 
support for cvars/concmds. Besides having two new commands ("meta cmds", 
"meta cvars"), it will also provide new macros for properly registering 
ConCommandBases.

Currently, your code might look like this:
Code:

bool MyAccessor::RegisterConCommandBase(ConCommandBase *pCommand)
{
    pCommand->SetNext(0);
    pICvar->RegisterConCommandBase(pCommand);

    return true;
}

To prevent crashing, you should instead register your ConCommandBases 
through SourceMM. SourceMM will then keep track of them and properly 
unlink them from the HL2 engine when needed. To do this, use the handy 
new macro:
Code:

bool MyAccessor::RegisterConCommandBase(ConCommandBase *pCommand)
{
    META_REGCVAR(pCommand);

    return true;
}

Want to see an example of this code, or test the code out before the 
next release? You can build SourceMM from CVS, and sample_mm in CVS has 
updated code demonstrating correct cvar/concmd usage.

    ---David "BAILOPAN" Anderson
    http://www.sourcemod.net/
    http://www.sourcemm.net/