Bug#893557: thin-provisioning-tools: FTBFS with glibc 2.17

[Steve Langasek]

On Tue, Mar 20, 2018 at 08:47:41AM +0100, Bastian Blank wrote:
> Hi Steve

> On Mon, Mar 19, 2018 at 03:37:17PM -0700, Steve Langasek wrote:
> > Ok, after some trial and error, I've determined that the reason my earlier
> > test succeeded was because I had built the test preload.so without the
> > benefit of dpkg-buildflags, which means -O3, which is used by default for
> > ppc64el on Ubuntu, was missing from the commandline.

> It is a bug in the compiler if it fails to compile a valid program with
> -O3.  So I don't see what this would fix.

Considering debian/rules also hardcodes -O2 for the package itself, it
doesn't seem inappropriate to also build the test shim with the same
options?

Yes, this is working around a toolchain issue.  Feel free to reassign this
bug to the toolchain, if you prefer.

FWIW I was able to identify a symbol reference that drops out of the .so
when built with -O3 but is present when built with -O2; this may be the
cause of the crash:

-0000000000000000      DF *UND* 0000000000000000  GLIBC_2.17  0x60 __stack_chk_fail

And perhaps that points to an explanation of the toolchain bug.

It's annoyingly difficult to debug this crash, as gdb doesn't appear to let
me DTRT with 'set env LD_PRELOAD' and instead manages to crash itself before
handing control over to the process under test.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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