W1021 Comparison always evaluates to False (Object Pascal)

From Appmethod Topics
Jump to: navigation, search

Go Up to Error and Warning Messages (Object Pascal) Index

The compiler has determined that the expression will always evaluate to False. This most often can be the result of a boundary test against a specific variable type, for example, a Integer against $80000000.

In versions of the Object Pascal compiler prior to 12.0, the hexadecimal constant $80000000 would have been a negative Integer value, but with the introduction of the int64 type, this same constant now becomes a positive int64 type. As a result, comparisons of this constant against Integer variables will no longer behave as they once did.

As this is a warning rather than an error, there is no standard method of addressing the problems: sometimes the warning can be ignored, sometimes the code must be rewritten.

program Produce;

    i : Integer;
    c : Cardinal;

  c := 0;
  i := 0;
  if c < 0 then

  if i >= $80000000 then

Here the compiler determines that the two expressions will always be False. In the first case, a Cardinal, which is unsigned, can never be less than 0. In the second case, a 32-bit Integer value can never be larger than, or even equal to, an int64 value of $80000000.