Planetarion Forums

Eidron · 21 Jul 2004, 11:08

I need one of these. Any help? Lol. Basically I have BBC programs and I need to try and decompile them. I havent found one for basic yet...

sayonara · 21 Jul 2004, 11:34

Errr... I don't think Basic is compiled.

If so that's probably why there are no decompilers for it.

JetLinus · 21 Jul 2004, 15:34

Quote:

Originally Posted by sayonara

Errr... I don't think Basic is compiled.
If so that's probably why there are no decompilers for it.

Yes it is. At least Visual Basic is. You still have a (non-default) option to create P-Code-Exes (pseudo-code), but who the hell would want to use that (for obvious reasons, like speed)?

And when speaking about "decompilers": There is no such thing, that could really "help" you getting back the code. Variable-Names, Procedure-, Function-, Object-Names, all gone. Comments too ofc. And things (e.g. loops) might not even look like they were programmed (many different ways can lead to one version of machine code).

It's always nice play around with decompilers, but I don't know anybody (including myself) who wasn't really disappointed after trying...

Mind you, I'm not talking about disassemblers and debuggers here, and their incredible usefulness when it comes to debugging & hacking.
Also a decompiler sure might help if you know EXACTLY what you're doing.

P.S.: What is BBC Basic? It might really be an interpreter only...

sayonara · 21 Jul 2004, 15:39

Quote:

Originally Posted by JetLinus

Yes it is. At least Visual Basic is.

He's talking about BBC Basic.

10 REM my new program
20 Print "Hello World"
30 GOTO 10

...And so on.

JetLinus · 21 Jul 2004, 15:46

If somebody isn't able to figure out that whether he has plaintext sourcecode files or binary executables, the complexity of a decompiler* will kill him (by causing his head to explode)...

* Don't be afraid of notepad

queball · 21 Jul 2004, 20:25

Good BBC BASIC compilers existed but I didn't see them used much. Source is so much nicer.

BBC BASIC source did however use a tokenised format rather than (or as well as) plaintext.

Raging.Retard · 22 Jul 2004, 17:29

Quote:

Originally Posted by JetLinus

And when speaking about "decompilers": There is no such thing, that could really "help" you getting back the code. Variable-Names, Procedure-, Function-, Object-Names, all gone. Comments too ofc. And things (e.g. loops) might not even look like they were programmed (many different ways can lead to one version of machine code).

It's always nice play around with decompilers, but I don't know anybody (including myself) who wasn't really disappointed after trying...

Just because you dont have the variable names, doesn't mean the code is gibberish? Any decent commercial decompiler can detect things like loops and beautify them for you as well.

JetLinus · 23 Jul 2004, 09:55

Quote:

Originally Posted by Raging.Retard

Just because you dont have the variable names, doesn't mean the code is gibberish?

Well, uhm, YES?

Take

Code:

ShipPosX = ShipPosX + (ShipVelocityX * (LastFrameTime / 1000))

What would you think about

Code:

VarA1 = VarA1 + (VarA7 * (VarB5 / 1000))

IMO almost ALL the understandability of good sourcecode comes from cleverly choosen variable and function names.

And about the loop stuff: There are different ways to "code" the same algorithm, how can you be sure the decompiler spits out exactly the nesting etc as in the source?
Ok, let's say it does: Still, without an idea what the loop indexes are, what exit conditions and why, and what arrays and offsets are looped throug, you're pretty fcked*.

* I know I know, disassembling and hardcore-debugging (as well as hacking, whatever) is all about exactly this. But in a real world, it's pretty much too hard and pointless, right?