The Wiert Corner - irregular stream of stuff: jpluimers

Wow, did I really wrote that 18 years ago?

Yes I did, and I was quoted in the (back then famous) FAQPAS3.TXT from (now Professor Emeritus) Timo Salmi: The third set of frequently (and not so frequently) asked Turbo Pascal questions with Timo’s answers. The items are in no particular order.

From ts@uwasa.fi Fri Nov 8 00:00:56 1996
Subject: Decompiling a TP .EXE

56.
Q: How can I reverse a TP .EXE or .TPU back into source code?

A: This is simply asking too much. You cannot decompile a TPprogram in a manner that would give you back the original source.This method of reverse engineering is not on in actual practice.

Quoting Jeroen Pluimers jeroenp@dragons.nest.nl

“During thecompilation, important information gets lost about variables,types, identifiers etc. Writing a Pascal Decompiler is impossible.The best you can achieve is a disassembler that can help yourecognize some Pascal statements.”

Since then I learned that compilers emit highly predictable CPU code that – with the right, and sometimes complex, algorithms – can be reconstructed into language structures.

Of course you are missing the identifiers and comments, but you can some remarkable info, especially with well structured code.

Two more links about this:

• Decompiling Delphi. (on Delphi.about.com)
  
• reverse engineering – Delphi decompiling – Stack Overflow.

–jeroen

via: FAQPAS3.TXT.