On 02.02.2023 10:22, Michael Van Canneyt via fpc-devel wrote:
On Thu, 2 Feb 2023, Ondrej Pokorny via fpc-devel wrote:
On 02.02.2023 10:15, Michael Van Canneyt via fpc-devel wrote:
On Thu, 2 Feb 2023, Ondrej Pokorny via fpc-devel wrote:
I myself cannot think of any real use case of constref other than
hacks like the FreeAndNil in recent Delphi versions:
procedure FreeAndNil(const [ref] Obj: TObject);
that needs the ref because it changes it to nil (so is not really a
const - it used to be an untyped var). As a result FreeAndNil
allows you to happily pass read-only properties to it that are then
nilled.
Which is a clear violation of the concept of Const... :/
Exactly.
Probably an ill-advised "fix" to the problem that FreeAndNil accepted
an untyped var
and you could basically pass anything.
Yes. Solving one problem by creating a different one. The best would be
if the FreeAndNil declaration alternated between constref and untyped
var between builds. In that case you would be able to hunt both the
issues :)
Seriously, having a [loose] modifier would be much more useful, IMO:
FreeAndNil(var [loose] Obj: TObject);
That would allow you to pass any TObject descendant.
Ondrej
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