Re: [StrongED] Testing StrongHelp 2.90b1 (Urgent)

[Peter Young <pnyoung@xxxxxxxxxxxx>]

On 21 Mar 2017  Fred Graute <fjgraute@xxxxxxxxx> wrote:

> In message <mpro.on4bwl004yfpf0vz7.pittdj@xxxxxxxxxxxx>
>           David Pitt <pittdj@xxxxxxxxxxxx> wrote:

> [snip]

>> I have now seen the crash after looking at the NeXTBar 1.30 StrongHelp.
>> 
>> It is a bit weird, it does not immediately crash !StrongHelp, that happens
>> later on some other entirely innocent file.
>>
>> Paint gives a "Bad MODE" error but !StrongHlp can render it as can !Draw. A
>> "corrected" version of the file can be extracted from !Draw after which
>> there are no more crashes (yet?).

> The sprite itself is actually fine. It's the data in the squash file
> that is corrupted, there's some spurious data at the end.

> StrongHelp allocates space based on the original length that's given in
> the squash header. Because of the extra data the allocated output buffer
> is overrun. This corrupts the list of free blocks so next time SH needs
> to allocate memory (eg when opening a manual) it may hit the damaged
> part of this list and abort.

> Extracting the sprite and re-squashing it gets rid of the spurious data.
> This stops the corruption of the list of free blocks and therefore SH no
> longer crashes on manuals opened after the NeXTBar manual.

Thanks again, Fred. I've been having a bit of a chaotic time with the 
NeXTBar manual on this ARMX6 not always being willing to show its 
contents, and I wondered how I would extract the sprite when all I got 
trying to open the sprite file was the "bad mode" message. I looked at 
the copy of NeXTBar on VRPC, where I could see the contents, and saw 
that the sprite there wasn't squashed. I then managed to open the 
manual on the ARMX6, and copied over the unsquashed sprite. This seems 
to let the manual open without the sprite's being squashed, so I 
wonder if the squash is necessary.

Anyway, the problem seems now to be solved, with many thanks.

Best wishes,

Peter.

-- 
Peter Young (zfc Ir) and family
Prestbury, Cheltenham, Glos. GL52, England
http://pnyoung.orpheusweb.co.uk
pnyoung@xxxxxxxxxxxx

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