[tip:perf/core] perf tools: Fix a bug of segmentation fault

From: tip-bot for Yunlong Song
Date: Wed Feb 18 2015 - 13:41:58 EST

Commit-ID: 3a03005ff9445834f3d3b577a11bcbdbdf7a89cf
Gitweb: http://git.kernel.org/tip/3a03005ff9445834f3d3b577a11bcbdbdf7a89cf
Author: Yunlong Song <yunlong.song@xxxxxxxxxx>
AuthorDate: Fri, 13 Feb 2015 21:11:52 +0800
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Fri, 13 Feb 2015 11:38:43 -0300

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.


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

Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1423833115-11199-5-git-send-email-yunlong.song@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/parse-options.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/parse-options.c b/tools/perf/util/parse-options.c
index 4a015f7..4ee9a86 100644
--- 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
- for (int i = 0; subcommands[i]; i++)
- printf("%s ", subcommands[i]);
+ if (subcommands) {
+ for (int i = 0; subcommands[i]; i++)
+ printf("%s ", subcommands[i]);
+ }
default: /* PARSE_OPT_UNKNOWN */
if (ctx.argv[0][1] == '-') {
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