Re: [PATCH] elf: Add tests with a local IFUNC resolver [BZ #23937]

[Florian Weimer <fweimer at redhat dot com>]

* Rafal Luzynski:

> 4.03.2019 10:47 Rafal Luzynski <digitalfreak@lingonborough.com> wrote:
>> 
>> 2.03.2019 17:54 "H.J. Lu" <hjl.tools@gmail.com> wrote:
>> > 
>> > [...]
>> > GCC 6.4.1 and binutils 2.31 branch work for me on x86-64.
>> 
>> Still the same failure.
>> 
>> I've also checked a similar virtual machine on another physical
>> machine and again the same failure which confirms that it is not
>> anything specific to one CPU model.
>> 
>> Does it maybe matter that all my tests are performed in virtual
>> machines controlled by VirtualBox?
>
> I've made several more tests during the weekend and it seems that
> it's GCC version what matters.  Just to summarize: my basic test
> environment is Fedora 24 (yes, I know, it is old) but I am able to
> install packages from newer versions.  I definitely have not tested
> every single version of GCC but 7.2.1-2 and everything newer worked
> fine while 7.1.1-3 and everything older failed at these tests.
> I did not touch binutils during these tests so I assume that its
> version does not matter.

I think this is GCC PR81128, see this comment:

  <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81128#c4>

The return value reported suggests that: it does look like an address in
the executable.

My motivation in adding this test case was to catch such bugs earlier
because clearly, the corresponding GCC tests are not prominent enough
(or do not cover all relevant usage scenarios).

> Thoughts?  Should we state that GCC 7.2 is a minimum required version
> to build Glibc?  Should these tests have additional checks and XFAIL
> in some versions of GCC?  Should we assume that the failures are
> correct and Glibc may be compiled with that particular version of GCC
> but only if GCC has some patches fixing any known bugs?

I think your use case is really unusual.  I expect that distributions
backport upstream bug fixes like this, and I assume Fedora did.  You
just didn't update back then.

Thanks,
Florian