Entry No.
451
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Compiler - Can't compile
Functions returning small objects give erroneous compiling error
message
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| 1.02 |
2.01 |
3.0 |
3.01 |
3.02 |
4.0 |
4.01 |
4.02 |
4.03 |
5.0 |
5.01 |
6.0 |
6.01 |
6.02 |
Kylix 1.0 |
| Absent | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists | Exists |
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Description | |
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Reported by Björn Sahlen; checked by Reinier Sterkenburg
The code below produces an error message ("Variable
required"). When the size of the object is incresed (n>4),
the error goes away.
This is a bug becasue:
- The compiler acts diferent depending on the size of the object.
- The compiler accepts the code if you use the with statement
instead of the dot notation (see the code example).
- The Automatic Code Completion will give you this option!
const
n = 4; // 1 to 4 not ok. >= 5 ok !
type
obj= object
b: array [1..n] of byte;
procedure proc;
end;
procedure obj.proc;
begin end;
function func: obj;
begin end;
var x: byte;
begin
x:= func.b[1]; // ok
with func do proc; // ok
func.proc; // Error: Variable required !!!
end. |
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Solution / workaround | |
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The only acceptable workaround for me is to use a record and standard
functions and procedures instead of an object. An other workaround is
of course to make sure that the size of your objects are at least five
bytes
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User-contributed comments | |
Chris R. Timmons
30 Jun 2001 10:08 PM GMT |
Not a bug. The example code is buggy, not Delphi.
Bug #1: An old-style "object" type is used. Use "class" instead:
type
obj = class(TObject)
Bug #2: function "func" doens't return an instance of obj. None of the code at the end of the example should work since there is no object instance to work on. Change func to:
function func : obj;
begin
Result := obj.Create;
end;
With those two fixes, the example code works fine in Delphi 5.01.
Jordan Russell
01 Jul 2001 07:06 PM GMT |
Sorry, but the example code is not buggy. Your understanding of old-style objects is buggy. :)
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