[DUG] Is it a bug in latest version of Delphi?

[Kyley Harris]

That sounds reasonable.

your last comment interests me.. we have been getting eOutofmemory errors in
logging very frequently on a machine that always has 4GB free ram :D

I'll have to research that more.

On Tue, Feb 16, 2010 at 3:06 PM, Jolyon Smith <jsmith at 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.
>
>
>
> Unfortunately, the Win API return value is ALSO the “Item data” value.  So
> if you store -1 and get -1 back it *could* be an error or it *could* be
> the valid result.
>
>
>
> The VCL *assumes* that if it gets -1 back then it must be an error.  It
> then makes matters worse by further *assuming* that it must be a list
> index error.
>
>
>
> What it *should* do is check the list index provided **itself** BEFORE
> sending that index to the WinAPI and then simply give the caller back
> whatever value the WinAPI yields (or at least raise LastOSError, not some
> assumed exception class).  This is a case of the VCL trying to be too
> helpful and making a botched job of it in the process.
>
>
>
> And as I pointed out, it is now (as of Delphi 2006 at least) fixed (poorly,
> imho, but still effectively fixed) in comboboxstrings, just not
> listboxstrings.
>
>
>
>
>
> It is similar to the error handling in *TWinControl.GetDeviceContext()*that naively assumes that a
> *GetDCEx()* result of 0 (zero) must indicate an *EOutOfResources*condition.  That bit of “intern code” cost me many lost hours trying to
> track down a resource leak when the true problem was actually an invalid
> window handle !!!**
>
>
>
>
>
> *From:* delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]
> *On Behalf Of *Kyley Harris
> *Sent:* Tuesday, 16 February 2010 2:51 p.m.
>
> *To:* NZ Borland Developers Group - Delphi List
> *Subject:* Re: [DUG] Is it a bug in latest version of Delphi?
>
>
>
> interesting
>
>
>
> >    if Longint(Result) = LB_ERR then Error(SListIndexError, Index);
>
>
>
> it would seem that the error is not in delphi at all. Well.. they are
> simply raising the Windows error which say that -1 is the error result for a
> bad index access from windows. if delphi were to ignore this error and you
> asked for the value at index[99] which was out of bounds and you got -1
> instead of an error I think there would be the same number of complaints
> from the other side.
>
>
>
> Clearly its the windows API that considers -1 invalid.. not delphi.
>
> On Tue, Feb 16, 2010 at 2:24 PM, Karl Reynolds <
> kreynolds at chocfishsoft.co.nz> wrote:
>
> On Tue, Feb 16, 2010 at 1:55 PM, Alister Christie
> <alister at salespartner.co.nz> wrote:
> > I think the point I was trying to make is that it is that the method
> > (/array indexer or whatever) was expecting a TObject - passing anything
> > else could result in unexpected results.
>
> Only if you stipulate that you have to remain ignorant of the function
> internals. The TObject is converted back and forth from a LongInt in
> order to store it anyway (see GetObject and PutObject).
>
>
> > The fact that -1 doesn't work
> > is therefor not a bug (unless you can have 1 byte sized objects).
>
> var x: longint;
>
> x := -1; // Four bytes
>
> (May the source be with you).
>
> Cheer,
> Karl
>
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>
> --
> Kyley Harris
> Harris Software
> +64-21-671-821
>
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-- 
Kyley Harris
Harris Software
+64-21-671-821
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