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    SubjectRe: [PATCH 1/5] perf: fix broken union in perf_event_mmap_page
    On Fri, Jun 28, 2013 at 04:22:17PM +0300, Adrian Hunter wrote:
    > The capabilities bits must not be "union'ed" together.
    > Put them in a separate struct.
    >
    > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
    > ---
    > include/uapi/linux/perf_event.h | 8 +++++---
    > 1 file changed, 5 insertions(+), 3 deletions(-)
    >
    > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
    > index 0b1df41..19f6ee5 100644
    > --- a/include/uapi/linux/perf_event.h
    > +++ b/include/uapi/linux/perf_event.h
    > @@ -375,9 +375,11 @@ struct perf_event_mmap_page {
    > __u64 time_running; /* time event on cpu */
    > union {
    > __u64 capabilities;
    > - __u64 cap_usr_time : 1,
    > - cap_usr_rdpmc : 1,
    > - cap_____res : 62;
    > + struct {
    > + __u64 cap_usr_time : 1,
    > + cap_usr_rdpmc : 1,
    > + cap_____res : 62;
    > + };
    > };

    Ick, it did that!? and here I thought there was a difference between:

    int foo:1,
    bar:1;

    and

    int foo:1;
    int bar:1;

    That made all the difference in this particular case. I guess I should
    go read the language spec more carefully next time.


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