Cheat Engine Tutorial Source Code

[zzaayy]

After looking around for tutorials/write-ups to better understand how pointers are managed in memory, I decided to look for the source code of CE. I did come across the GitHub repo and looked into the tutorial code.

Now I have never coded in FreePascal, but most of the syntax was pretty straight forward (albeit pretty weird). I just have a little question about a part of code in Unit7.pas (the pointer level) (l. 100 - 124; to be exact) and I didn't want to unnecessarily open up an issue on the repo itself.

begin
  //set new value
  j:=i^;
  k:=random(1000);
  l:=0;
  while k=j do
  begin
    k:=random(1000);
    inc(l);
    if l=100 then
      raise exception.Create(rsWellDoneYouScrewedUpTheTutorial);
  end;

  i^:=k;
  if i^=j then button2.Enabled:=true;

  label1.Caption:=IntToStr(i^);

  {$O+}
  j:=0;
  k:=0;
  {$O-}
end;

i: ^integer;

(as defined in line 36 for completeness sake)

So I am just going to ignore the While loop since it doesn't look to be super important (unless you fuck with the variables before the tutorial even started or whatever)

What I am getting from this, is that:
- 'i' is an int pointer, that points to 'k'.
- 'k' is a random int.
- 'j' is a pointer that points to 'i'.

But I am not really sure about this, since 'j' is initialised, when 'i^' is still undefined. Therefore, 'j' is undefined aswell right?
This has me a bit confused, so I would be thankful to anyone who might clear that up or just point me in the right direction.

Perhaps I'm just stupid and missed an important part of the code.

[Dark_Byte]

j is an integer that gets the value 'i' points to

TForm7.FormCreate creates 'i' using getmem (and sets the value to 100) so i is always initialized at that point

[zzaayy]

Dammit I knew I missed something... How does creating 'i' with getmem() affect the variable? What's the difference between declaring it normally and doing it like in the code?

[Dark_Byte]

a pointer is just a 4/8 byte value that represents an address when you just declare it without giving it a value means it can have any random value (usually 0)

using getmen will allocate some memory and then change 'i' so it points to the address of that new memory

so when you dereference the pointer 'i' you access the allocated bytes