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
