Thx Jon this is very helpful.  Indeed the memblock was malloc'd so no
way that RB can check it.

I'm curious, this crash info is impressive, how does the OS gather
this data and what kind of overhead is required when you consider
millions of function calls per second as an app executes?

Peter.

On 5/6/06, Jonathan Johnson <[EMAIL PROTECTED]> wrote:

On May 6, 2006, at 10:43 AM, Peter K. Stys wrote:
> I assume this is the call chain with the most recent (and presumably
> offending) call at the top?

Yes.

> Question: are these logs reliable and should I be indeed looking for a
> bad memBlock.ushort access that is referencing an invalid address?

Yes. They're exactly where the application crashed at.

> I'm left wondering because I wrote a small test app that calls several
> methods in turn, with the last one deliberately accessing non-existent
> memory.  That crash log did not contain any of the method names that
> were sequentially called to trigger the crash.

It only reports the current call stack, not the previous one. Your
crash log shows that inside of imageDisplayWindow,
updateToolsWindowInfo calls displayCoordsAndPixelvalues, which calls
calcRGBPixelValues, which then calls MemoryBlock.UShort.

Most likely the memory block in question is one that REALbasic doesn't
know the bounds of, because REALbasic will normally check the bounds to
ensure you don't read past your buffer. It sounds like you're reading
past the end of the bounds to your allocated memory, which the crash
type:

Exception:  EXC_BAD_ACCESS (0x0001)
Codes:      KERN_INVALID_ADDRESS (0x0001) at 0x081790e0

Infers also. Or, it could be that the value the memoryblock was freed
elsewhere, or something like that.

HTH,
Jon


--
Jonathan Johnson
REAL Software, Inc.

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Peter K. Stys, MD
Professor of Medicine(Neurology), Senior Scientist
Ottawa Health Research Institute, Div. of Neuroscience
Ottawa Hospital / University of Ottawa
Ontario, CANADA
tel:    (613)761-5444
fax:    (613)761-5330
http://www.ohri.ca/profiles/stys.asp
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