linux/tools
Jiri Olsa b39c2a57a0 perf tools: Fix strict alias issue for find_first_bit
When compiling perf tool code with gcc 4.4.7 I'm getting
following error:

    CC       util/session.o
  cc1: warnings being treated as errors
  util/session.c: In function ‘perf_session_deliver_event’:
  tools/perf/util/include/linux/bitops.h:109: error: dereferencing pointer ‘p’ does break strict-aliasing rules
  tools/perf/util/include/linux/bitops.h:101: error: dereferencing pointer ‘p’ does break strict-aliasing rules
  util/session.c:697: note: initialized from here
  tools/perf/util/include/linux/bitops.h:101: note: initialized from here
  make[1]: *** [util/session.o] Error 1
  make: *** [util/session.o] Error 2

The aliased types here are u64 and unsigned long pointers, which is safe
for the find_first_bit processing.

This error shows up for me only for gcc 4.4 on 32bit x86, even for
-Wstrict-aliasing=3, while newer gcc are quiet and scream here for
-Wstrict-aliasing={2,1}. Looks like newer gcc changed the rules for
strict alias warnings.

The gcc documentation offers workaround for valid aliasing by using
__may_alias__ attribute:

  http://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Type-Attributes.html

Using this workaround for the find_first_bit function.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1393434867-20271-1-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2014-02-28 10:39:40 -03:00
..
cgroup
firewire
hv Tools: hv: remove inclusion of linux/types.h 2013-12-08 22:47:12 -08:00
include tools include: Include <linux/compiler.h> from asm/bug.h 2014-01-13 10:14:13 -03:00
lguest
lib perf tools: Fix traceevent plugin path definitions 2014-01-23 15:48:12 -03:00
net bpf_exp: free duplicated labels at exit time 2013-12-17 17:11:00 -05:00
nfsd
perf perf tools: Fix strict alias issue for find_first_bit 2014-02-28 10:39:40 -03:00
power Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2014-02-02 11:28:48 -08:00
scripts tools lib traceevent: Add global QUIET_CC_FPIC build output 2013-12-19 16:18:10 -03:00
testing test: check copy_to/from_user boundary validation 2014-01-23 16:36:57 -08:00
thermal/tmon tools/thermal: Introduce tmon, a tool for thermal subsystem 2013-11-07 08:45:34 +08:00
usb usb: tools: fix a regression issue that gcc can't link to pthread 2013-12-04 15:10:54 -08:00
virtio
vm tools/: Convert to new topic libraries 2013-12-16 16:03:27 -03:00
Makefile ACPI and power management updates for 3.14-rc1 2014-01-24 15:51:02 -08:00