Re: [PATCH 1/1] perf tests hwmon_pmu: Use PRIu64 + (u64) cast for a __u64 field to work more widely

[David Laight]

On Thu, 28 May 2026 12:55:45 -0700
Ian Rogers <irogers@xxxxxxxxxx> wrote:

> On Thu, May 28, 2026 at 12:53 PM Arnaldo Carvalho de Melo
> <arnaldo.melo@xxxxxxxxx> wrote:
> >
> > While testing perf with an updated Debian experimental cross compiler
> > (gcc version 14.2.0 (Debian 14.2.0-13)) this started failing:
> >
> >   In file included from tests/hwmon_pmu.c:12:
> >   tests/hwmon_pmu.c: In function 'do_test':
> >   tests/hwmon_pmu.c:199:34: error: format '%lld' expects argument of type 'long long int', but argument 7 has type '__u64' {aka 'long unsigned int'} [-Werror=format=]
> >     199 |                         pr_debug("FAILED %s:%d Unexpected config for '%s', %lld != %ld\n",
> >         |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   /git/perf-7.1.0-rc5/tools/perf/util/debug.h:20:21: note: in definition of macro 'pr_fmt'
> >      20 | #define pr_fmt(fmt) fmt
> >         |                     ^~~
> >   tests/hwmon_pmu.c:199:25: note: in expansion of macro 'pr_debug'
> >     199 |                         pr_debug("FAILED %s:%d Unexpected config for '%s', %lld != %ld\n",
> >         |                         ^~~~~~~~
> >   tests/hwmon_pmu.c:199:79: note: format string is defined here
> >     199 |                         pr_debug("FAILED %s:%d Unexpected config for '%s', %lld != %ld\n",
> >         |                                                                            ~~~^
> >         |                                                                               |
> >         |                                                                               long long int
> >         |                                                                            %ld
> >     LD      /tmp/build/perf/util/intel-pt-decoder/perf-util-in.o
> >
> > The usual make that %lld a PRIu64 (since arg7 is
> > evsel->core.attr.config, which is a __u64) but then on Fedora 44 (gcc
> > version 16.1.1 20260515 (Red Hat 16.1.1-2)) it ends up with:
> >
> >   In file included from tests/hwmon_pmu.c:13:
> >   tests/hwmon_pmu.c: In function ‘do_test’:
> >   tests/hwmon_pmu.c:200:34: error: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 7 has type ‘__u64’ {aka ‘long long unsigned int’} [-Werror=format=]
> >     200 |                         pr_debug("FAILED %s:%d Unexpected config for '%s', %" PRIu64 " != %ld\n",
> >         |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   /home/acme/git/perf-tools-next2/tools/perf/util/debug.h:20:21: note: in definition of macro ‘pr_fmt’
> >      20 | #define pr_fmt(fmt) fmt
> >         |                     ^~~
> >   tests/hwmon_pmu.c:200:25: note: in expansion of macro ‘pr_debug’
> >     200 |                         pr_debug("FAILED %s:%d Unexpected config for '%s', %" PRIu64 " != %ld\n",
> >         |                         ^~~~~~~~
> >   cc1: all warnings being treated as errors
> >
> > So the way to satisfy both compilers is to also add a (u64) cast to
> > arg7.  
> 
> As the inttypes.h definitions match stdint.h would it make more sense
> to use uint64_t for the cast?

Or use (unsigned long long) and "%lld".
Using PRIu64 and a cast is the worst of both worlds.

Where does the definition of __u64 come from?
#define __u64 @@
at the top of a file might give a clue.
I thought it was a Linux kernel type matching u64 - which is always 'unsigned long long'.

-- David

> 
> Thanks,
> Ian
> 
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > ---
> >  tools/perf/tests/hwmon_pmu.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/tests/hwmon_pmu.c b/tools/perf/tests/hwmon_pmu.c
> > index ada6e445c4c41e1b..870d59c0f7cba2e7 100644
> > --- a/tools/perf/tests/hwmon_pmu.c
> > +++ b/tools/perf/tests/hwmon_pmu.c
> > @@ -2,6 +2,7 @@
> >  #include "hwmon_pmu.h"
> >
> >  #include <errno.h>
> > +#include <inttypes.h>
> >
> >  #include <fcntl.h>
> >  #include <linux/compiler.h>
> > @@ -196,9 +197,9 @@ static int do_test(size_t i, bool with_pmu, bool with_alias)
> >                         continue;
> >
> >                 if (evsel->core.attr.config != (u64)test_events[i].key.type_and_num) {
> > -                       pr_debug("FAILED %s:%d Unexpected config for '%s', %lld != %ld\n",
> > +                       pr_debug("FAILED %s:%d Unexpected config for '%s', %" PRIu64 " != %ld\n",
> >                                 __FILE__, __LINE__, str,
> > -                               evsel->core.attr.config,
> > +                               (u64)evsel->core.attr.config,
> >                                 test_events[i].key.type_and_num);
> >                         ret = TEST_FAIL;
> >                         goto out;
> > --
> > 2.54.0
> >  
>