Re: Fix some ubsan/asan related issues

Hi,

On 2024-01-30 22:05:28 +0200, Heikki Linnakangas wrote:
> On 30/01/2024 17:57, Tristan Partin wrote:
> > In my effort to try to see if the test suite would pass with asan
> > enabled, I ran into a max_stack_depth issue. I tried maxing it out
> > (hence, the patch), but that still didn't remedy my issue. I tried to
> > look on the list for any relevant emails, but nothing turned up. Maybe
> > others have not attempted this before? Seems doubtful.
> >
> > Not entirely sure how to fix this issue. I personally find asan
> > extremely effective, even more than valgrind, so it would be great if
> > I could run Postgres with asan enabled to catch various stupid C issues
> > I might create. On my system, ulimit -a returns 8192 kbytes, so Postgres
> > just lets me set 7680 kbytes as the max. Whatever asan is doing doesn't
> > seem to leave enough stack space for Postgres.
>
> I'm a bit confused by these. We already run with sanitizer in the cirrus CI.
> What does this enable that we're not already doing?

The reason asan fails is that it uses a "shadow stack" to track stack variable
lifetimes. These confuse our stack depth check. CI doesn't have the issue
because the compiler doesn't yet enable the feature, locally I get around it
by using ASAN_OPTIONS=detect_stack_use_after_return=0:...

The checks are actually quite useful, so making our stack depth check work
with asan would be worthwhile.

I discussed this in a bit more in
https://postgr.es/m/20231129193920.4vphw7dqxjzf5v5b%40awork3.anarazel.de

Greetings,

Andres Freund