Famous Last Words: You can't decompile a C++ program

The Great Jack Schitt writes "I've always heard that you couldn't decompile a program written with C++. This article describes how to do it. It's a bit lengthy and it doesn't seem like the author usually writes in English, but it might just work (haven't tried it, but will when I have time)."

Comments

You can't

[Anonymous Coward]

Information is lost in compilation. You can never reconstruct the exact original source. You end up with valid C++ that has no more human-understandable information than the equivilent machine code.

Like turning hamburgers into cows...

Re:You can't

[capnjack41]

And then on top of that, the compiler optimizes that code, so calculations are no longer the straightforward and intuitive things they used to be, now they're a series of out-of-order, smaller calculations that are harder to recognize. They're efficient as hell but barely reversible.

I'll RTFA when it comes back to life :).

Re:You can't

[jkorty]

Information is lost in compilation. You can never reconstruct the exact original source

So what? Doing reasonable interpolations in context is what brains are for. Example: IIRC, when the Morris Worm appeared in 1989, Gene Spafford examined the binary and reverse-engineered the C code, sprinkling it with meaningful comments and good variable and function names. When the original source became available, his turned out to be cleaner program than the original. That is, he not only recreated the original in every way that counts, he overshot and did better than the original

Why not?

[bazik]

I've always heard that you couldn't decompile a program written with C++.

Well, you can decompile every binary programm at least to assembler code, so why shouldnt it possible with C++?

Maybe he ment "you can't decipher the source of a C++ programm" ;)

Re:Why

[Anonymous Coward]

You need reasons?

1) Finding backdoors
2) Testing security
3) Fixing bugs
4) Adding features
5) Discovering copyright violations
6) Interfacing to non-supported clients

Pretty much anything and everything you would do if you had the source.

Re:Why

[p4ul13]

You could be updating a program for your company for which the source is lost.

Inline functions, templates and decompilation

[truth_revealed]

Sure you can decompile an optimized and symbol-stripped C++ program, but you'd never have it the original compact form of the source as you do with the Java class file decompilers due to the heavy use of inline functions and templates used in C++. A C program, sure, but decompiling C++ is not terribly useful.

Reverse engineering has its uses...

[sheetsda]

There seem to be a lot of people in this story saying "shame on you for reverse engineering". It has its uses, how else would viruses, worms, and trojans be analyzed to figure out what they do and how they do it.

Re:Why

[Lumpy]

Why would you want to do this unless you were stealing source?


nice try.

You must be either Bill Gates, Steve Ballmer or someone who works for the BSA.

How am I to tell if your close source program isn't full of my GPL code that you blatently stole and are trying to rob me blind by STEALING my IP? Being a closed source advocate as you seem to be you are for me trying to detect IP theft and the illegal STEALING of my code by PIRATES right?

Ok, I'm going overboard to make my point... I have EVERY right to use tools in a good and legal way. Why not outlaw hammers as anyone can perform a very grisly and horrible murder with one... Or better yet only allow licensed contractors to have hammers! as we know that the unlicensed public is only going to do very ewvil things with tools!

see my point now? A tool is exactly what it looks like.... a tool. it can be used for good and evil. and I dont have any respect for the self righteous like you condemning what I do before I even do it.

people with attitudes like you are what cause all the pain and suffering in this world...... STOP IT!