safety: null checks

Patrick Schluter Patrick.Schluter at bbox.fr
Tue Nov 24 08:47:03 UTC 2020


On Tuesday, 24 November 2020 at 00:08:57 UTC, Ola Fosheim Grostad 
wrote:
> On Monday, 23 November 2020 at 20:00:29 UTC, Patrick Schluter 
> wrote:
>> On Monday, 23 November 2020 at 12:39:05 UTC, Ola Fosheim 
>> Grøstad wrote:
>>> A trap is an interrupt at the hardware level. It has nothing 
>>> to do with C.
>>
>> Read the C standard, they explain what a trap representation 
>> is. It has nothing to do with an interrupt. I refer to the C 
>> standard because they make the difference between allowed 
>> pointer values and unallowed values even if never dereferenced.
>
> When I intoduced the word "trap" in this discussion I used the 
> traditional hardware terminology as used in Motorola 68K 
> reference manuals. Has nothing to do with C whatsoever.

I introduced the expression "trap representation" from the C 
standard (and I specified explicitly the context I said "null is 
not a trap representation as a C standard would call it.").
Understanding this as meaning the 68000 trap# instruction can 
only be done either in bad faith, either from stupidity*. Choose 
your case.

Bye, no further involvement from my part.

* I know it's a false dichotomy, there's a third possibility but 
it is not positive for you either (you misunderstood and are too 
proud to admit it).


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