> On Sep 9, 2017, at 3:15 AM, Jean-Daniel <[email protected]> wrote: > > >> 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
Thanks, I was being a bit silly... We also have malloc_good_size(4097) = 4608. What I was getting at is, can malloc_good_size be “dumb” for any legal implementation of malloc zones? Or can we assert malloc_good_size(x) == malloc_size(malloc(x)? -Andy _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
