Hi, Tom! Thank you for taking care of this.
On Mon, Feb 8, 2021 at 3:47 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > > [ redirecting to -hackers ] > > Alexander Korotkov <aekorot...@gmail.com> writes: > >> BTW, I managed to reproduce the issue by compiling with CFLAGS="-O0 > >> -fsanitize=alignment -fsanitize-trap=alignment" and the patch > >> attached. > >> I can propose the following to catch such issues earlier. We could > >> finish (wrap attribute with macro and apply it to other places with > >> misalignment access if any) and apply the attached patch and make > >> commitfest.cputube.org check patches with CFLAGS="-O0 > >> -fsanitize=alignment -fsanitize-trap=alignment". What do you think? > > > The revised patch is attached. The attribute is wrapped into > > pg_attribute_no_sanitize_alignment() macro. I've checked it works for > > me with gcc-10 and clang-11. > > I found some time to experiment with this today. It is really nice > to be able to detect these problems without using obsolete hardware. > However, I have a few issues: > > * Why do you recommend -O0? Seems to me we want to test the code > as we'd normally use it, ie typically -O2. My idea was that with -O0 we can see some unaligned accesses, which would be optimized away with -O2. I mean with -O2 we might completely skip accessing some pointer, which would be accessed in -O0. However, this situation is probably very rare. > * I think the right place to run such a check is in some buildfarm > animals. The cfbot only sees portions of what goes into our tree. Could we have both cfbot + buildfarm animals? ------ Regards, Alexander Korotkov
