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>

1 files changed, 28 insertions, 34 deletions

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index cd2fb42e5dd4..ac59710b79e0 100644
--- 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,