I think this is popping up in Hacker News because the concept of decompilers has become a bit more acceptable recently. (strokes beard)Time was, decompilation was said to be Impossible (as my wise friend syke said: most things people say are impossible are just tedious). Then, it just became "something you could only do in a targeted, single-application fashion.)

Somewhere in there, Alan Kaye laughed and handed everyone dynamic code.

These days, with AI in tow, decompilation is becoming the sort of thing that could be in the toolchain, replacing IDA and such. Why debug and examine when you can literally decompile?!

So, maybe, that idea being considered to be newly on the table, someone felt the need to post a counter-point, proving once again that everything old is new again.

Hats off for decomiling Java apps that mostly predate generics and annotations... both of which were added in 5.

▲

branko_d an hour ago | parent | next [-]

Is there anything especially hard about decompiling (to) Java?

.NET/C# decompilers are widespread and generally work well (there is one built into Visual Studio nowdays, JetBrains have their own, there were a bunch of stand-alone tools too back in the the day).

	▲	leibnitz27 19 minutes ago \| parent [-]
		< disclaimer - I wrote CFR, which is one of the original set of 'modern' java decompilers > Generic erasure is a giant pain in the rear. C# doesn't do this. You don't actually keep any information about generics in the bytecode, however some of the metadata is present. BUT IT COULD BE FULL OF LIES. There's also a huge amount of syntactic sugar in later java versions - take for example switch expressions. https://www.benf.org/other/cfr/switch_expressions.html and OH MY GOD FINALLY https://www.benf.org/other/cfr/finally.html

▲

darkamaul 2 hours ago | parent | prev [-]

One of the use case of décompilation is bug hunting / vulnerability research. And that’s still one of the use cases where AI isn’t that good because you must be precise.

I’m not saying that won’t change but I still see a bright future for reversing tools, with or without AI sidekicks (like the BN plugin)

	▲	hhh an hour ago \| parent [-]
		I used codex 5.1 yesterday to point at a firmware blob and let it extract and explore it targeting a specific undisclosed vulnerability and it managed (after floundering for a bit) to read the Lua bytecode and identify and exploit the vuln on a device running the firmware.