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Re: [std-proposals] set_new_handler extension

From: Jason McKesson <jmckesson_at_[hidden]>
Date: Sun, 12 Feb 2023 11:28:10 -0500
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.

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

Furthermore... they could just call `RtlAllocateHeap` themselves
manually. You cannot *make* someone not call some function.
*Especially* across DLL boundaries.

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.

Received on 2023-02-12 16:28:49