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

hmm

[Graspee_Leemoor]

A c/c++ decompiler that totally worked would be the Holy Grail of crackers. Unfortunately it is actually impossible to get everything back because lots of info is lost on compilation.

Nevertheless there are tools out there that attempt to decompile programs; I think of them more as ways of making assembly more readable.

Note, a lot of them wouldn't work on hand-written assembly, because they rely on knowledge of how certain compilers compile various things- e.g. there was a Delphi decompile available.

graspee

sure you can go from asm - c++

[Anonymous Coward]

but it'll look like this

class a
{
public:
void b(int c);
void d(int e);
private:
int g;
int h;
};

int main()
{
a f;
f.b(23);

int x; x=0; x++;
if(x > 3) goto j;
f.d(x); x++
if(x > 3) goto j;
f.d(x); x++;
if(x > 3) goto j;
f.d(x);
j: f.b(42);

return 0;
}

Spectulation Code

[Davak]

Considering the entire post is evidently based on speculation...

Here is some code that supposedly decomplies... not that I've tried it.

Quote from the FAQ:

[35.4] How can I decompile an executable program back into C++ source code?

You gotta be kidding, right?

Here are a few of the many reasons this is not even remotely feasible:
* What makes you think the program was written in C++ to begin with?
* Even if you are sure it was originally written (at least partially) in C++,
which one of the gazillion C++ compilers produced it?
* Even if you know the compiler, which particular version of the compiler was
used?
* Even if you know the compiler's manufacturer and version number, what
compile-time options were used?
* Even if you know the compiler's manufacturer and version number and
compile-time options, what third party libraries were linked-in, and what
was their version?
* Even if you know all that stuff, most executables have had their debugging
information stripped out, so the resulting decompiled code will be totally
unreadable.
* Even if you know everything about the compiler, manufacturer, version
number, compile-time options, third party libraries, and debugging
information, the cost of writing a decompiler that works with even one
particular compiler and has even a modest success rate at generating code
would be significant -- on the par with writing the compiler itself from
scratch.

But the biggest question is not how you can decompile someone's code, but why
do you want to do this? If you're trying to reverse-engineer someone else's
code, shame on you; go find honest work. If you're trying to recover from
losing your own source, the best suggestion I have is to make better backups
next time.

I would have posted AC but that have me blocked out for some reason...

Davak