PrintPreview and Range Checking

[sebybar]

I found that the PrintPreview Component raise a runtime error if you compile it with the range checking option.
Try to compile the General Demo project and move the scroll bar.
Is it dangerous for my application?

[Johnny_Bit]

Range Checking is only for debuging matters, it slows down whole application. If you're writing good code, range checking could be allways off.

This is dangerous if your application is more than tinny and yo're trying to run it on slow computer (e.g. lest than 333MHz)

[sebybar]

Yes, I know that.
But I meant another thing:
If a range checking error is raised, it means that something is going wrong with the procedure. Is it a bug? Is it a serious bug?

Range Checking is only for debuging matters, it slows down whole application. If you're writing good code, range checking could be allways off.

This is dangerous if your application is more than tinny and yo're trying to run it on slow computer (e.g. lest than 333MHz)

[Kambiz]

It's not always because of an out of range index reference. Sometimes the range check code (added by compiler) makes a mistake, specially on parameters of API calls.

[Kambiz]

There's something wrong in the following code?

Code: Select all

type
  PByteArray = ^TByteArray;
  TByteArray = array[0..0] of Byte;
var
  pba: PByteArray;
  I: Integer;
begin
  GetMem(pba, 100);
  try
    for I := 0 to 99 do
      pba[I] := I;
    // The rest of code
  finally
    FreeMem(pba);
  end;
end.

Absolutely not! However, when range checking is on, a run-time error will terminate the program.