Hacker News Reader

Comment by Gigachad | Hacker News Reader

Identical output isn’t ridiculous. It’s pretty much a requirement to ensure the game actually is the same in every way. These decomp projects are pitched as a high performance alternative to emulation.

No one is going to use it if it’s a kind of close but not really reimplementation.

Testing functional equivalence is also pretty much impossible. How would you for example test the new one has exactly the same bugs which haven’t been discovered yet. Or doesn’t introduce new ones? This stuff matters for speed runners.

View on HN

It’s ridiculous because something as simple as the compiler picking different registers is going to make zero functional difference but give a false negative on assembly compare.

Yet the C code can’t pick what registers to use, so the poor agent is probably shuffling the code around randomly for hours or days until it matches.

That’s probably why the agent dropped down into inline assembly in the first place (the author complained about this), because I bet it’s thinking trace was that this is futile.

Compilers themselves are not even deterministic and running them multiple times creates different assembly.

> Yet the C code can’t pick what registers to use, so the poor agent is probably shuffling the code around randomly for hours or days until it matches.

Humans too do that for matching decompilation. Or at least I imagine so, given that I personally refuse to do that.

People have different goals and will use different techniques to achieve them. The video game reverse-engineering/decompilation community isn't a hive-mind, I went ahead and created ghidra-delinker-extension because I had my own ideas on how to do that.

How do you know the original code didn't use some undefined variable on stack, but happened to consistently work because something else spilled a register containing "suitable" value?

I think I disagree when it comes to bug reproduction. Doesn't seem I'm alone in that.

Isn't MW2 rooted in id tech engines? Last I checked there was raw assembly inside the code base. I would have started with quake 2/3 whatever source code and tried to match that up with Claude first - some of it has to have survived (though I doubt much)

Reply on news.ycombinator.com