Include UndefinedBehavior Sanitizer to our CI

[RafaelGSS]

Hi!

Are we interested in including an Undefined Behavior Sanitizer (pretty similar to our test-asan) in our CI workflow?

I know that currently, our CI takes a quite long time to conclude (considering flaky tests), but, undefined behavior is very often harmful to compiler assumptions and eventually, makes a branch slower.

I made a test including this flag only on macOS (just to test a particular case), but in case we concur on having this as an option I can pursue this work. See https://github.com/nodejs/node/compare/main...RafaelGSS:node:build/incldue-ub-build?expand=1

Interested in hearing your thoughts @nodejs/build @richardlau @addaleax

[bnoordhuis]

undefined behavior is very often harmful to compiler assumptions and eventually, makes a branch slower

It's the other way around: UB gives the compiler a free pass to completely optimize away buggy code. :-)

Something to investigate is if V8 is ubsan-clean nowadays. It didn't used to be (v8:3770) but I see there's an ubsan buildbot now and a -fsanitize=undefined switch in BUILD.gn so... maybe?

[RafaelGSS]

From my local tests, only small-icu isn't ubsan-clean.

[bnoordhuis]

I've opened a tracking issue for libuv: libuv/libuv#3869

I believe libuv is in reasonably good shape already but we'll see.

[bnoordhuis]

libuv/libuv#3870 - libuv has a ubsan CI bot now (and it's clean.)

[RafaelGSS]

Excellent. I think we could skip the small-icu for now, what do you think? In the case of affirmative, I can open the PR to include the workflow.

[bnoordhuis]

Sounds good.