On Fri, Feb 28, 2014 at 06:25:51PM -0300, Arnaldo Carvalho de Melo wrote: > From: Jiri Olsa <[email protected]> > > 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.
Hurm; didn't I suggest using -fno-strict-aliasing just like the kernel does? Because the C aliasing rules are bonghits heavy? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
