[PATCH v3] build: allow turning off --no-undefined and -z,defs

[Mark Wielaard]

Hi Evgeny,

I really appreciate you helping us using more analyzers and fuzzers to
improve the code base. I think the address sanitizer already helped
improve the code. But it would help if you replied to the original
reviews and/or mentioned how the different versions of your patch have
changed since the last time. As far as I can see you only changed the
commit message a little this time.

On Fri, Dec 03, 2021 at 06:02:09PM +0000, Evgeny Vereshchagin wrote:
> Other than that, while options like --enable-sanitize-undefined are
> helpful shortcuts, they simply can't cover all the usecases and it's
> still necessary to pass additional compiler flags to clang via
> CFLAGS to for example get around issues like
> https://github.com/evverx/elfutils/issues/16 and
> https://github.com/evverx/elfutils/issues/15.

I really do believe that working from the now proposed
--enable-sanatize-address will be easiest to integrate address
sanitizer support. See how I used it to workaround isssues with the
gcc address sanitizer. You can use it likewise to work around issues
with clang. e.g. the configure check should detect the issue with
--no-undefined and could try if adding -lasan to LDFLAGS helps.

So the other isssues you are seeing with the clang address sanitizer
is "applying non-zero offset ... to null pointer" and "variable length
array bound evaluates to non-positive value 0". I am not sure how
those are actual problems. In the first case the calculated addresses
aren't actually used as (dereferenced) pointers, in the second the
array bound being zero also means the array content isn't used. Do you
know why these issues are flagged? Are there any extra ASAN_OPTIONS
set in these cases?

Cheers,

Mark