touch-packages team mailing list archive

[Anders Kaseorg <andersk@xxxxxxx>]

I’ve written a test case that clearly demonstrates the GCC 4.8 bug
responsible for the kadmin.local failure:

$ gcc-4.8 -Wall -O2 bug.c -o bug
$ ./bug
$ echo $?
1
$ gcc-4.9 -Wall -O2 bug.c -o bug
$ ./bug
$ echo $?
0

A git bisection of the GCC source shows that this bug disappeared in
https://gcc.gnu.org/r202525. However, I don’t understand why; the fact
that r202525 was intended to fix a “missed-optimization” bug
(https://gcc.gnu.org/PR58404) is a little bit terrifying.

** Also affects: gcc-4.8 (Ubuntu)
   Importance: Undecided
       Status: New

** Attachment added: "Reduced test case for GCC 4.8 bug"
   https://bugs.launchpad.net/ubuntu/+source/krb5/+bug/1347147/+attachment/4165776/+files/bug.c

-- 
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to gcc-4.8 in Ubuntu.
https://bugs.launchpad.net/bugs/1347147

Title:
  krb5 database propagation enters infinite loop

Status in “gcc-4.8” package in Ubuntu:
  New
Status in “krb5” package in Ubuntu:
  Confirmed

Bug description:
  In some conditions, propagating a kerberos database to a slave KDC server can stall.
  This is due to a misoptimization by gcc 4.8 of the CIRCLEQ famliy of macros, apparently due to overzealous strict aliasing deductions.

  One case of this stall is reported at
  http://mailman.mit.edu/pipermail/kerberos/2014-July/020007.html (and
  the rest of the thread), and there is an entry in the upstream
  bugtracker at http://krbdev.mit.edu/rt/Ticket/Display.html?id=7860 .

  gcc 4.9 (as used in Debian unstable at present) is not believed to
  induce this problem.  Upstream has patched their code to use the TAILQ
  family of macros instead, as a workaround, but that workaround has not
  yet appeared in an upstream release:
  https://github.com/krb5/krb5/commit/26d8744129

  Because of the different compiler versions used on Debian and Ubuntu,
  I am filing this as an Ubuntu-specific bug.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.8/+bug/1347147/+subscriptions