Null pointer in __vptr

Ali Çehreli acehreli at
Fri Nov 19 21:09:16 UTC 2021

On 11/19/21 10:04 AM, frame wrote:
 > On Friday, 19 November 2021 at 15:46:41 UTC, Adam D Ruppe wrote:
 >> The `destroy` function (as well as other class destruction) will null
 >> out the whole vtable to help make use-after-free an obvious error.
 >> Possible that happened to you.
 > So, a partial nulled table shouldn't exist, right? like this:
 > __vptr[0]: address
 > __vptr[1]: 0000000
 > __vptr[2]: address
 > __vptr[3]: address
 > __vptr[4]: address
 > __vptr[5]: address
 > ....
 > Because 0 should point to the object instance

I am not sure that's correct. The way I picture it, the code reaches the 
__vptr by following a pointer; so it's already known. Additionally, I am 
under the impression that there is only one __vptr for a given type, 
which all class objects of that type point to.

 > and next offsets are pointers to the member functions, correct?

My understanding is that all entries are that.


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