Re: [PATCH] driver core: faux: fix Undefined Behavior in faux_device_destroy()

[Alice Ryhl]

On Mon, Jun 16, 2025 at 5:36 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Sat, Jun 14, 2025 at 07:53:34AM -0700, Marc Herbert wrote:
> > > the kernel relies on this not being "optimized away" by the compiler
> > > in many places.
> >
> > I think "undefined behavior" is the more general topic, more important
> > than null pointer checks specifically?
>
> Is this really "undefined behaviour"?  There are a lot of things that
> the kernel requires for a compiler to be able to build it, and this is
> one of those things, it can't do this type of "optimization" and expect
> the output to actually work properly.

My understanding is that -fno-delete-null-pointer-checks changes the
language semantics so that nullptr deref isn't UB anymore and instead
becomes a guaranteed crash.

Alice