Comment by fm77 | Hacker News Reader

Comment by fm77 | Hacker News Reader

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This may sound like a contradiction to you because you are right, this is not the official source code of Turbo Pascal, but it is the source code of Turbo Pascal.... :-)

Barry also stated this 5 years ago, see

https://news.ycombinator.com/item?id=10202563

but that is not true.

How can I be so sure? I reverse-engineered pretty much all Turbo Pascal versions starting with v4.0 all the way up to v8.0 (Delphi v1.0). I even disassembled the beta versions of Delphi, v7.9h and v7.9k, to see and study the transition from Turbo Pascal to Delphi.

That being said, what you are looking at at turbopascal.org is an absolute mind-blowing reverse-engineering job. One hint is when you look for example at

Procedure AddReferenceRecordForTypedConstant (UnitSegment, BlockRecord: Word; ReferenceFlags: TReferenceFlagSet; DX, TypedConstantOffset: Word);

https://turbopascal.org/processing-typed-constants

at the bottom of the page - where the author couldn't come up with a proper name for the DX register, so he left that identifier unchanged. If you disassemble Turbo Pascal "tpc.exe" and look for that subroutine you'll see that Anders Hejlsberg really used the DX register.... (I know, not really convincing...)

If I understood right - this is a "white box" reimplementation of the real Turbo Pascal, which uses the same algorithms and structures and control flow as the real one (and therefore should be bug-for-bug compatible) but is written in Pascal instead of assembly? That is, the "DX" argument there isn't actually passed in register DX, but it represents a function call in real Turbo Pascal that passed the same semantic contents in register DX?

I don't know what a "white box" reimplementation is (white-box cryptography?) but I guess you meant a clean room implementation (https://en.wikipedia.org/wiki/Clean_room_design) which I believe this is not the case here (I am wild guessing though). For a clean room implementation you need at least two guys, one reverse engineer who writes down his findings and a guy who takes that information and reimplements the same functionality according to the information the reverse-engineer provides.

But you are right in that it uses the same algorithms, structures and control flow as the real Turbo Pascal and therefore should be bug-for-bug compatible but is written in Pascal instead of assembly.

Probably a poor choice of words, but I mean the opposite of a clean room reimplementation - it's one where the same person is looking at disassembly and writing the new implementation (i.e, the thing being reimplemented is a white box, not a black box).

Interesting!

Isn't original TP7 source code available?

https://github.com/shidel/DustyTP7

You have linked a source code repository of programs and units written for TP7.

The sources of TP6 have leaked a few years ago. Search for exmortis on HN.

That "sources of TP6" you are referring to is not a leak but also a fantastic reverse-engineering job done probably 1993/94 and appeared 20 years ago on the web...

In this context, it's a really impressive work! Can you tell us more?

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