[PATCH v2] build: allow turning off --no-undefined and -z,defs

[Mark Wielaard]

Hi Evgeny,

On Fri, Dec 03, 2021 at 02:17:21PM +0000, Evgeny Vereshchagin wrote:
> ASan, UBSan and MSan provided by clang aren't compatible with --no-undefined and -z,defs:
> https://clang.llvm.org/docs/AddressSanitizer.html#usage
> https://github.com/google/sanitizers/issues/380
> so to build elfutils with clang with the sanitizers it should be possible
> to turn them off.

I have to agree with Florian, this really is a bug in the compiler you
are using.  Adding -fsanitize=address to CFLAGS/CXXFLAGS works just
fine with gcc.  I have been using it in the past in combination with
the afl fuzzer (32bit only).  It doesn't work together with
--enable-valgrind though.

That said, I really would like to add address sanitizer support. It
would be great to add this to our buildbot CI to catch more issues
early. We already support --enable-sanitize-undefined and
--enable-valgrind. But sadly we have to disable valgrind in a couple
of testcases, specifically when testing the debuginfod server.

I just testing with gcc (Debian 10.2.1-6) 10.2.1 20210110 on arm64 and
it actually found some issues. I'll post patches for those.

There is one issue with the test-nlist test because we use special
CFLAGS for that. But if we introduce an --enable-sanitize-address we
could work around that.

If clang really cannot be fixed then your patch in combination with an
--enable-sanitize-address might be a good idea. But I don't think it
makes sense as a standalone option. In the past we made the mistake of
adding configure options to disable some necessary flags, like
--disable-symbol-versioning, which was a mistake. There are now
distros shipping elfutils libraries with broken abis while using the
same SONAMEs.

Cheers,

Mark