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Re: [std-proposals] set_new_handler extension

From: Phil Bouchard <boost_at_[hidden]>
Date: Sun, 12 Feb 2023 11:43:10 -0500
On 2/12/23 11:28, Jason McKesson via Std-Proposals wrote:
> On Sun, Feb 12, 2023 at 9:55 AM Phil Bouchard via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
>> On 2/12/23 09:05, Sebastian Wittmeier via Std-Proposals wrote:
>>> Hi Phil,
>>> can you ellaborate on the reliability issues of RtlAllocateHeap()?
>>> Are you talking about out-of-memory conditions or heap corruption with
>>> HEAP_NO_SERIALIZE in multi-threading scenarios or about performance in
>>> those cases?
>>> Are there reliability issues even without HEAP_NO_SERIALZE? Then
>>> RtlAllocateHeap() violates the Windows API specification.
>> No I do not use HEAP_NO_SERIALZE so it should be "thread-safe".
>>> Or you want C++ to provide facilities to provide ways to avoid/replace
>>> RtlAllocateHeap() for reliability or compliance reasons for the whole
>>> application, even for static and dynamic libraries, which have been
>>> directly linked to it?
>> In brave new world that's exactly what I would hope for. A memory pool
>> is not very complicated to implement using the following possible
>> characteristics:
>> - thread-local for faster and safer accesses;
>> - type-oriented to group block sizes together and to create less
>> fragmentation;
>> - allocation rate to extrapolate future memory page allocation size;
>> - possible "reallocation";
>> - possible destruction of heap pages with or without calling destructors;
>> - ...
>> So anyway there's a lot of factors that can be considered and I would
>> have hoped to replace low-level memory pools with custom-ones. But the
>> only way to achieve this is by standardizing linkers.
> I don't see how "standardizing linkers" helps anything with regard to
> the problem you're talking about.
> What you want is to be able to globally replace what the default
> `operator new` and `operator delete` do, even outside of the current
> translation unit. That's not a linker problem; that's a problem in how
> `operator new/delete` *work*.
> In order to be able to replace them as you desire, these functions
> have to stop being static function calls and become *dynamic* function
> calls. That is, the static code needs to look for a registered
> function pointer and call that. That is the *only way* to make this
> work across translation units that did not see the global override.
> That's not a linker issue; that's an issue with how code works.

Yeah or "virtual" function calls that can be overriden whatever the
client wants to use them for.

So I guess what I am trying to suggest are: virtual operator new () and
delete() function calls.

> And it doesn't even fix the problem universally because code compiled
> before this change *cannot* be made to use the new dynamic function.
> There's no way to modify the compiled binary to find where they call
> `operator new` because such code may have been (and likely was)
> inlined. And it may even be an ABI break, but I'm not an expert on
> that.
> Furthermore... they could just call `RtlAllocateHeap` themselves
> manually. You cannot *make* someone not call some function.
> *Especially* across DLL boundaries.

Yeah that's fine because Windows at least upgrades their compiler
quickly regarding the latest standards; I give them that.

> What you want is simply not viable.
>> If you search engine search on Rtl*Heap() functions then this problem
>> lasted for a long time and all related bug reports were simply
>> dismissed. I think it's time to turn the page on those issues.
> That's not how the burden of proof works. You don't get to say that
> there's a problem with a thing and we need a workaround, and when
> asked for evidence of that problem then say go find it yourself.
> I mean you *can* say that, since you just did. But it's not exactly a
> reasonable response.
> And for what it's worth, I did spend a few minutes Googling the issue.
> And the only incidents I found where any actual investigation was done
> (ie: something more than "a program crashed and the stack trace named
> this function") all resolved down to application-caused heap
> corruption. Which... is not a problem even your suggestion could
> actually fix.

My goal here is to find solutions to problems; not to find problems to

Memory allocations are a huge cybersecurity problem (70%) and needs to
be fixed at all layers, starting with core allocations routines. That's
an undeniable fact.


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Received on 2023-02-12 16:43:11