linux/tools/perf
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
..
arch perf tools: Introduce zfree 2013-12-27 15:17:00 -03:00
bench perf bench: Fix two warnings 2013-11-01 10:41:54 -03:00
config perf tools: fix BFD detection on opensuse 2014-02-27 18:29:08 -03:00
Documentation perf record: Rename --initial-delay to --delay 2014-01-14 17:58:12 -03:00
python perf python: Remove duplicate TID bit from mask 2013-08-07 17:35:25 -03:00
scripts perf tools: Finish the removal of 'self' arguments 2013-11-05 15:32:36 -03:00
tests perf tests: No need to set up ref_reloc_sym 2014-01-31 17:21:52 -03:00
ui perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
util perf tools: Fix strict alias issue for find_first_bit 2014-02-28 10:39:40 -03:00
.gitignore perf tools: Ignore 'perf timechart' output file 2013-10-11 12:17:37 -03:00
builtin-annotate.c perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
builtin-bench.c perf bench: Change the procps visible command-name of invididual benchmark tests plus cleanups 2013-10-23 09:57:34 -03:00
builtin-buildid-cache.c perf buildid-cache: Check relocation when checking for existing kcore 2014-01-31 17:21:54 -03:00
builtin-buildid-list.c perf session: Separating data file properties from session 2013-10-21 17:33:25 -03:00
builtin-diff.c perf diff: Color the Weighted Diff column 2014-01-13 11:38:25 -03:00
builtin-evlist.c perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
builtin-help.c perf help: Fix --help for builtins 2012-10-22 12:35:49 -02:00
builtin-inject.c perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
builtin-kmem.c perf evsel: Ditch evsel->handler.data field 2013-11-07 10:40:47 -03:00
builtin-kvm.c perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
builtin-list.c perf list: Add usage 2013-11-05 14:26:41 -03:00
builtin-lock.c perf evsel: Ditch evsel->handler.data field 2013-11-07 10:40:47 -03:00
builtin-mem.c perf mem: Remove unused parameter from dump_raw_samples() 2013-12-19 17:03:39 -03:00
builtin-probe.c perf probe: Release all dynamically allocated parameters 2014-01-16 16:29:02 -03:00
builtin-record.c perf record: Get ref_reloc_sym from kernel map 2014-01-31 17:21:50 -03:00
builtin-report.c perf annotate: Check availability of annotate when processing samples 2014-02-24 11:12:55 -03:00
builtin-sched.c perf tools: Use zfree to help detect use after free bugs 2013-12-27 17:08:19 -03:00
builtin-script.c perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
builtin-stat.c perf evlist: Introduce evlist__for_each() & friends 2014-01-13 10:06:25 -03:00
builtin-timechart.c perf timechart: Fix wrong SVG height 2014-01-20 16:19:08 -03:00
builtin-top.c perf annotate: Check availability of annotate when processing samples 2014-02-24 11:12:55 -03:00
builtin-trace.c perf trace: Fix ioctl 'request' beautifier build problems on !(i386 || x86_64) arches 2014-02-13 17:28:31 -03:00
builtin.h perf tools: Add new mem command for memory access profiling 2013-04-01 12:21:44 -03:00
command-list.txt perf tools: Add new mem command for memory access profiling 2013-04-01 12:21:44 -03:00
CREDITS perf_counter tools: Add CREDITS file for Git contributors 2009-06-24 19:54:29 +02:00
design.txt perf/doc: Remove mention of non-existent set_perf_event_pending() from design.txt 2014-01-26 09:37:48 +01:00
Makefile perf tools: Add 'build-test' make target 2014-01-16 16:26:26 -03:00
Makefile.perf perf: tools: Fix cross building 2014-01-15 15:15:05 -03:00
MANIFEST perf tools: Include tools/lib/api/ in MANIFEST 2014-01-13 10:06:26 -03:00
perf-archive.sh perf archive: Make 'f' the last parameter for tar 2012-09-17 13:10:42 -03:00
perf-completion.sh perf completion: Complete 'perf kvm' 2013-12-13 10:30:21 -03:00
perf.c tools/: Convert to new topic libraries 2013-12-16 16:03:27 -03:00
perf.h perf tools: Fix AAAAARGH64 memory barriers 2014-01-29 15:50:57 -03:00