perf evsel: Do not put a variable sized type not at the end of a struct

As this is a GNU extension and while harmless in this case, we can do
the same thing in a more clearer way by using a existing thread_map and
cpu_map constructors:

With this we avoid this while compiling with clang:

  util/evsel.c:1659:17: error: field 'map' with variable sized type 'struct cpu_map' not at the end of a struct or class is a GNU extension
        [-Werror,-Wgnu-variable-sized-type-not-at-end]
          struct cpu_map map;
                         ^
  util/evsel.c:1667:20: error: field 'map' with variable sized type 'struct thread_map' not at the end of a struct or class is a GNU extension
        [-Werror,-Wgnu-variable-sized-type-not-at-end]
          struct thread_map map;
                            ^
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-207juvrqjiar7uvas2s83v5i@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index cd2fb42e5dd4d00efc49614e76d5f27984c22f63..ac59710b79e0b4cbee35cacc1e40a2102e091d8e 100644 (file)
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1448,8 +1448,8 @@ static bool ignore_missing_thread(struct perf_evsel *evsel,
        return true;
 }
 
-static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
-                             struct thread_map *threads)
+int perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
+                    struct thread_map *threads)
 {
        int cpu, thread, nthreads;
        unsigned long flags = PERF_FLAG_FD_CLOEXEC;
@@ -1459,6 +1459,30 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
        if (perf_missing_features.write_backward && evsel->attr.write_backward)
                return -EINVAL;
 
+       if (cpus == NULL) {
+               static struct cpu_map *empty_cpu_map;
+
+               if (empty_cpu_map == NULL) {
+                       empty_cpu_map = cpu_map__dummy_new();
+                       if (empty_cpu_map == NULL)
+                               return -ENOMEM;
+               }
+
+               cpus = empty_cpu_map;
+       }
+
+       if (threads == NULL) {
+               static struct thread_map *empty_thread_map;
+
+               if (empty_thread_map == NULL) {
+                       empty_thread_map = thread_map__new_by_tid(-1);
+                       if (empty_thread_map == NULL)
+                               return -ENOMEM;
+               }
+
+               threads = empty_thread_map;
+       }
+
        if (evsel->system_wide)
                nthreads = 1;
        else
@@ -1655,46 +1679,16 @@ void perf_evsel__close(struct perf_evsel *evsel, int ncpus, int nthreads)
        perf_evsel__free_fd(evsel);
 }
 
-static struct {
-       struct cpu_map map;
-       int cpus[1];
-} empty_cpu_map = {
-       .map.nr = 1,
-       .cpus   = { -1, },
-};
-
-static struct {
-       struct thread_map map;
-       int threads[1];
-} empty_thread_map = {
-       .map.nr  = 1,
-       .threads = { -1, },
-};
-
-int perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
-                    struct thread_map *threads)
-{
-       if (cpus == NULL) {
-               /* Work around old compiler warnings about strict aliasing */
-               cpus = &empty_cpu_map.map;
-       }
-
-       if (threads == NULL)
-               threads = &empty_thread_map.map;
-
-       return __perf_evsel__open(evsel, cpus, threads);
-}
-
 int perf_evsel__open_per_cpu(struct perf_evsel *evsel,
                             struct cpu_map *cpus)
 {
-       return __perf_evsel__open(evsel, cpus, &empty_thread_map.map);
+       return perf_evsel__open(evsel, cpus, NULL);
 }
 
 int perf_evsel__open_per_thread(struct perf_evsel *evsel,
                                struct thread_map *threads)
 {
-       return __perf_evsel__open(evsel, &empty_cpu_map.map, threads);
+       return perf_evsel__open(evsel, NULL, threads);
 }
 
 static int perf_evsel__parse_id_sample(const struct perf_evsel *evsel,