perf tools: Fix a bug of segmentation fault

Fix the 'segmentation fault' bug of 'perf list --list-cmds', which also
happens in other cases (e.g. record, report ...). This bug happens when
there are no cmds to list at all.

Example:

Before this patch:

  $ perf list --list-cmds
  Segmentation fault
  $

  After this patch:
  $ perf list --list-cmds
  $

As shown above, the result prints nothing rather than a segmentation
fault. The null result means 'perf list' has no cmds to display at this
time.

Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1423833115-11199-5-git-send-email-yunlong.song@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/parse-options.c b/tools/perf/util/parse-options.c
index 4a015f77e2b5bb6ff7f6ab3e8c22ec42bf1b8b67..4ee9a86705ed3a84d02dda86ff20e1099078c853 100644 (file)
--- a/tools/perf/util/parse-options.c
+++ b/tools/perf/util/parse-options.c
@@ -510,8 +510,10 @@ int parse_options_subcommand(int argc, const char **argv, const struct option *o
                }
                exit(130);
        case PARSE_OPT_LIST_SUBCMDS:
-               for (int i = 0; subcommands[i]; i++)
-                       printf("%s ", subcommands[i]);
+               if (subcommands) {
+                       for (int i = 0; subcommands[i]; i++)
+                               printf("%s ", subcommands[i]);
+               }
                exit(130);
        default: /* PARSE_OPT_UNKNOWN */
                if (ctx.argv[0][1] == '-') {