i tested getlasterror also and it does not fail when an invalid index is
returned.
As i mentioned earlier.. index[99] will not fail.. you just get -1 :D
pre-testing the range is the only bypass. or.. just store your data in a
structure thats kinder to -1 :)
On Tue, Feb 16, 2010 at 3:57 PM, Jolyon Smith <jsm...@deltics.co.nz> wrote:
> Good luck with GetLastError(). There's nothing to indicate that
> LB_GETITEMDATA processing will set a Windows "LastError".
>
> And empirically I would have to say that it doesn't:
>
> // On an empty Listbox1 ..
>
> r := SendMessage(Listbox1.Handle, LB_GETITEMDATA, 100, 0);
> if GetLastError <> 0 then
> RaiseLastOSError;
>
> if r = -1 then
> ShowMessage('oops');
>
>
> Will yield only the "oops" message, no OS error.
>
> I am speculating (in this case I don't have the source for SendMessage() or
> the LISTBOX wndproc) that SendMessage() isn't setting an error condition
> (after all it is successfully sending a message and returning the result)
> and that the LISTBOX wndproc doesn't SetLastError() when processing
> LB_GETITEMDATA, at least not for an invalid item index.
>
>
>
> > -----Original Message-----
> > From: delphi-boun...@delphi.org.nz [mailto:delphi-
> > boun...@delphi.org.nz] On Behalf Of Karl Reynolds
> > Sent: Tuesday, 16 February 2010 3:29 p.m.
> > To: NZ Borland Developers Group - Delphi List
> > Subject: Re: [DUG] Is it a bug in latest version of Delphi?
> >
> > On Tue, Feb 16, 2010 at 3:06 PM, Jolyon Smith <jsm...@deltics.co.nz>
> > wrote:
> > > Win API returns -1 to indicate “an error”. Any error. Not a
> > specific
> > > error. Certainly not specifically a list index error.
> >
> > Pardon me for being pedantic, but while I agree with everything else
> > you said, I feel the need to reiterate that -1 isn't actually returned
> > to *indicate* an error (and you mentioned the conflict between an
> > error result and a valid result yourself at one point). It's just the
> > value returned when an error has occured. And yes, that means the VCL
> > code is wrong.
> >
> > GetLastError... I won't say it again, promise. ;)
> >
> > Cheers,
> > Karl
> >
> > _______________________________________________
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>
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--
Kyley Harris
Harris Software
+64-21-671-821
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