> Le 8 sept. 2017 à 03:03, Andrew Trick via swift-evolution 
> <[email protected]> a écrit :
> 
> 
>> On Sep 7, 2017, at 5:37 PM, Joe Groff <[email protected]> wrote:
>>> 
>>> The important thing is that the UnsafeBufferPointer API is clearly 
>>> documented. We do not want users to think it’s ok to deallocate a smaller 
>>> buffer than they allocated.
>>> 
>>> Unfortunately, there’s actually no way to assert this in the runtime 
>>> because malloc_size could be larger than the allocated capacity. Incorrect 
>>> code could happen to work and we can live with that.
>> 
>> Would it be sufficient to assert that malloc_good_size(passedCapacity) == 
>> malloc_size(base) ? It wouldn't be perfect but could still catch a lot of 
>> misuses.
> 
> That theory does hold up for a million random values, but I don’t know if we 
> can rely on malloc_size never being larger than roundUp(sz, 16). Greg?

You can’t. This may be true while alloc size if less than a page, but a quick 
test show that:

malloc_size(malloc(4097)) = 4608


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