Why is this an issue?

Local variables must be initialized before use to ensure the code behaves deterministically and in an error-free manner.

Unlike object fields and global variables, contents of local variables are generally undefined until initialized. The only exceptions are the following managed types:

• Strings
• Variants
• Interfaces
• Arrays of the above types

How to fix it

Assign the variable with an initial value before using it.

procedure GetCount(MyList: TList);
var
  ListSize: Integer;
begin
  if (MyList.Count > 0) then begin
    ListSize := MyList.Count;
  end;

  Writeln(Format('The list has %d elements', [ListSize]));
end;

procedure GetCount(MyList: TList);
var
  ListSize: Integer;
begin
  ListSize := 0;
  if (MyList.Count > 0) then begin
    ListSize := MyList.Count;
  end;

  Writeln(Format('The list has %d elements', [ListSize]));
end;

Resources

• Stack Overflow: Are delphi variables initialized with a value by default?
• RAD Studio documentation: Variables (Delphi)