Can you find this Delphi coding error (part 1)?

June 1, 2016

Can you spot the error in the following Delphi code? The code consists of a typical function that returns a sum of values.

function CalcNetResult : Integer;
var
  I, Sum : Integer;
begin
  Result := GetInitialAmount;

  for I := 1 to GetNumParts do
    Inc(Sum, GetPartAmount(I));

  Inc(Result, Sum);
end;

Well, that was not too hard, was it?

Solution: The local variable Sum has not been initialized before the for-loop, and will contain a random value. The function result will not be the expected. This is all because of the way local variables are managed in memory.

Not so hard to spot! But imagine finding this problem among thousands of lines of code spread over hundreds of units! And consider also a code base that is evolving all the time, so the code must constantly be rechecked.

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