percona-xtradb-cluster: FTBFS with gcc7.

[Jorge Niedbalski]

[Impact]

 * gcc 7 has new errors it detects as well as some extended logic to
   detect more cases of those error classes it had before. By that the
   transition to gcc-7 has broken the percona build.

 * There is no upstream fix to this already that can be backported, and
   the errors are too manifold to rewrite that much code without a risk.

 * Therefore wherever possible we just tell gcc to not consider the new
   warnings errors, despite otherwise runnign with -Werror

 * There are two cases that can't just be done via compiler flags:
   - a missing define that was caused by the former bugfix upload
   - a ISO format error that can't be made a Warning only with -Werror but
     is rather easy to fix.

[Test Case]

 * Build the package

[Regression Potential]

 * While the actual changes were minimized to only change as few code as
   possible to avoid negative effects there could be some. For example
   most of the comparisons fixed formerly had no effect, now they do so
   that might be a slight change. Never the less just compiling with the
   newer compiler might have had just as much effect. Tests by Niedibalski
   were good so it is not generally broken, but a subtle effect as
   described can't be eliminated by 100% - OTOH it should still be safe
   enough IMHO.

[Other Info]

 * The changes can be reviewed more easily in broken down commits at:
https://code.launchpad.net/~paelzer/ubuntu/+source/percona-xtradb-cluster-5.6/+git/percona-xtradb-cluster-5.6/+ref/bug-1657256-FTBFS-cleanup

 * The FTBFS would block SRU activity later on as well as currently is
   blocking an SRU to older releases which is waiting to have the fix in
   the new release as well.

 * This is certainly ok to be a 0day update and no need to affect the ISO,
   yet version wise I assumed this will happen before the copy for BB, so
   versions are still incrementing "normally", not in SRU style.

---

Multiple errors are being detected while compiling with the latest gcc included
in artful.

gcc-7-base ppc64el 7.2.0-2ubuntu1
libgcc1 ppc64el 1:7.2.0-2ubuntu1

Log for a recent build:

https://launchpad.net/ubuntu/+source/percona-xtradb-cluster-5.6/5.6.34-26.19-0ubuntu3/+build/13322626/+files/buildlog_ubuntu-artful-ppc64el.percona-xtradb-cluster-5.6_5.6.34-26.19-0ubuntu3_BUILDING.txt.gz

[Christian Ehrhardt  (paelzer)]

FYI - As the fix for this was attached to bug 1657256 I iterated on the fix there.

[Christian Ehrhardt  (paelzer)]

I proposed a branch and testable ppa in [1] based on my rework of the suggestion by Niedibalski.

That passed Tests on the actual issue, as well as review if the intended fix is retained.
In general it is much smaller now in Delta than what it was in the first proposal that got attached.

Since we are as Frozen as possible already I expect this to be an early SRU.
Therefore already prepping a SRU Template now.

[Christian Ehrhardt  (paelzer)]

[1]: https://code.launchpad.net/~paelzer/ubuntu/+source/percona-xtradb-cluster-5.6/+git/percona-xtradb-cluster-5.6/+merge/332357

[Christian Ehrhardt  (paelzer)]

SRU Template Prepped (since we are Freezing as much as possible), upload tag added and pushed for the importer.

I ran this buildpackage with -v5.6.34-26.19-0ubuntu2 as the current proposed build never hit the archive (due to this FTBFS). That should make sure all tools correctly pick up both affected bugs.

I see it in Artful-unapproved, so waiting for review by release or SRU Team (whatever applies when they get to it).

[Christian Ehrhardt  (paelzer)]

Just realized that this isn't seeded, so of course it passed faster after someone acked it in unapproved. Hoping that it now builds as fine as it did in the LP ppa.

[Christian Ehrhardt  (paelzer)]

Build worked fine, now waiting for tests in update_excuses.
But even then it might be blocked on the Freeze of todays release - I'll contact the release Team if nothing else blocks it.

[Launchpad Janitor (janitor)]

This bug was fixed in the package percona-xtradb-cluster-5.6 - 5.6.34-26.19-0ubuntu4

---------------
percona-xtradb-cluster-5.6 (5.6.34-26.19-0ubuntu4) artful; urgency=high

  [ Jorge Niedbalski ]
  * Fix FTBFS with gcc7 (LP: #1714554)
    - d/p/ibuf-uses-full-memory-barrier-ppc64.patch: Modified to prevent a
      warning at compile time due to the inexistence of the default os_mb.

  [ Christian Ehrhardt ]
  * Fix FTBFS with gcc7 - further fixes to LP 1714554
    - d/rules: make warnings new/enhanced in gcc7 non-fatal in regard to Werror:
      format-overflow, implicit-fallthrough, int-in-bool-context, nonnull,
      aligned-new (only c++), format-truncation
    - d/p/fix-gcc7-compiler-errors.patch: fix gcc-7 errors not downgradable
      to warnings (ISO C++ forbids comparison between pointer and integer)

percona-xtradb-cluster-5.6 (5.6.34-26.19-0ubuntu3) artful; urgency=high

  * d/p/ibuf-uses-full-memory-barrier-ppc64.patch: This patch implements
    a full memory barrier for InnoDB mutex entry/exit on PowerPC.
    (LP: #1657256).

  * d/p/debian/patches/weak-memory-compat.patch: Removed as is already
    covered by the newer patch.

 -- Christian Ehrhardt <email address hidden> Tue, 17 Oct 2017 10:16:36 +0200