Hi Peter,
On Wed, May 15, 2024 at 12:36 AM Peter Zijlstra <pet...@infradead.org> wrote:
>
> On Wed, May 08, 2024 at 04:47:25PM -0700, Linus Torvalds wrote:
> > For example, the most common case of overflow we've ever had has very
> > much been array indexing. Now, sometimes that has actually been actual
> > undefined behavior, because it's been overflow in signed variables,
> > and those are "easy" to find in the sense that you just say "no, can't
> > do that". UBSAN finds them, and that's good.
>
> We build with -fno-strict-overflow, which implies -fwrapv, which removes
> the UB from signed overflow by mandating 2s complement.
FWIW,
Clang-19 allows -fwrapv and -fsanitize=signed-integer-overflow to work
together [1]
And the sanitizer was re-introduced with Commit 557f8c582a9ba8ab
("ubsan: Reintroduce signed overflow sanitizer").
>
> With the exception of an UBSAN bug prior to GCC-8, UBSAN will not, and
> should not, warn about signed overflow when using either of these flags.
[1]: https://clang.llvm.org/docs/ReleaseNotes.html#sanitizers
Thanks
Justin
