perf report: Don't allow empty argument for '-t'.

Without this patch, perf report cause segfault if pass "" as '-t':

  $ perf report -t ""

   # To display the perf.data header info, please use --header/--header-only options.
   #
   # Samples: 37  of event 'syscalls:sys_enter_write'
   # Event count (approx.): 37
   #
   # Children    SelfCommand   Shared Object         Symbol
   Segmentation fault

Since -t is used to add field-separator for generate table, -t "" is
actually meanless. This patch defines a new OPT_STRING_NOEMPTY() option
generator to ensure user never pass empty string to that option.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: pi3orama@163.com
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1426251114-198991-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/tools/perf/util/parse-options.c b/tools/perf/util/parse-options.c
index 1457d6639b60..01626be2a8eb 100644
--- a/tools/perf/util/parse-options.c
+++ b/tools/perf/util/parse-options.c
@@ -37,6 +37,7 @@ static int get_value(struct parse_opt_ctx_t *p,
 {
 	const char *s, *arg = NULL;
 	const int unset = flags & OPT_UNSET;
+	int err;
 
 	if (unset && p->opt)
 		return opterror(opt, "takes no value", flags);
@@ -114,13 +115,29 @@ static int get_value(struct parse_opt_ctx_t *p,
 		return 0;
 
 	case OPTION_STRING:
+		err = 0;
 		if (unset)
 			*(const char **)opt->value = NULL;
 		else if (opt->flags & PARSE_OPT_OPTARG && !p->opt)
 			*(const char **)opt->value = (const char *)opt->defval;
 		else
-			return get_arg(p, opt, flags, (const char **)opt->value);
-		return 0;
+			err = get_arg(p, opt, flags, (const char **)opt->value);
+
+		/* PARSE_OPT_NOEMPTY: Allow NULL but disallow empty string. */
+		if (opt->flags & PARSE_OPT_NOEMPTY) {
+			const char *val = *(const char **)opt->value;
+
+			if (!val)
+				return err;
+
+			/* Similar to unset if we are given an empty string. */
+			if (val[0] == '\0') {
+				*(const char **)opt->value = NULL;
+				return 0;
+			}
+		}
+
+		return err;
 
 	case OPTION_CALLBACK:
 		if (unset)