When installing sys-auth/consolekit-0.4.3 on my Gentoo system, I received the following warnings:

 * QA Notice: Package has poor programming practices which may compile
 *            fine but exhibit random runtime failures.
 * ck-log-system-start.c:198: warning: dereferencing pointer ‘e’ does break strict-aliasing rules
 * ck-log-system-start.c:201: warning: dereferencing pointer ‘e’ does break strict-aliasing rules

 * Please do not file a Gentoo bug and instead report the above QA
 * issues directly to the upstream developers of this software.
 * Homepage: http://www.freedesktop.org/wiki/Software/ConsoleKit
 * ERROR: sys-auth/consolekit-0.4.3 failed:
 *   install aborted due to poor programming practices shown above


Looking through the build log itself, these appear to be the relevant lines:

  CC     ck-get-x11-display-device.o
  CCLD   ck-get-x11-display-device
  CC     ck-log-system-start.o
ck-log-system-start.c: In function ‘open_log_file’:
ck-log-system-start.c:103: warning: ignoring return value of ‘fchown’, declared with attribute warn_unused_result
ck-log-system-start.c: In function ‘main’:
ck-log-system-start.c:198: warning: dereferencing pointer ‘e’ does break strict-aliasing rules
ck-log-system-start.c:201: warning: dereferencing pointer ‘e’ does break strict-aliasing rules
ck-log-system-start.c:195: note: initialized from here
  CCLD   ck-log-system-start
  CC     ck-log-system-restart.o


Although I'm not sure how to fix these. Happy to provide details as required.