m68k/cpu32 TRAP instruction?

[Jeff Law]

On 10/5/18 3:53 PM, Segher Boessenkool wrote:
> On Fri, Oct 05, 2018 at 03:30:47PM -0600, Jeff Law wrote:
>> On 10/5/18 3:14 PM, Josef Wolf wrote:
>>>
>>> - If the compiler can detect such a serious problem, then it should emit a
>>>   warning AT COMPILE TIME.
>> We don't for various reasons.  Frankly, I think we should as well, but I
>> lost that battle.
> 
> There is -Wnull-dereference.
Yea, but our implementation is so lame that it's effectively useless.
It only warns out of the front-end and only does so for an explicit *0
that can be seen without any constant propagation or path isolation.

> 
> If you want the compiler to warn every time there *could* be a null
> dereference, well, how many false positives will that be?  ;-)
It's really not bad if you do it late and focus just on whether or not
you can see a NULL pointer flowing into a dereference.

I'd certainly agree that it'd be too noisy to warn if you had a random
pointer of unknown value that gets dereferenced.  It could be zero and
warning for all those would be useless in practice.



jeff