perf tools: Don't allow empty argument for field-separator

Both 'perf diff' and 'perf mem' have 'field-separator' option, which
causes segfault if passed with empty string. This patch uses previously
introduced 'OPT_STRING_NOEMPTY' option macro to prevent fault.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: pi3orama@163.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1426820272-23302-1-git-send-email-wangnan0@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-diff.c

@@ -802,7 +802,7 @@ static const struct option options[] = {
 	OPT_STRING('s', "sort", &sort_order, "key[,key2...]",
 		   "sort by key(s): pid, comm, dso, symbol, parent, cpu, srcline, ..."
 		   " Please refer the man page for the complete list."),
-	OPT_STRING('t', "field-separator", &symbol_conf.field_sep, "separator",
+	OPT_STRING_NOEMPTY('t', "field-separator", &symbol_conf.field_sep, "separator",
 		   "separator for columns, no spaces will be added between "
 		   "columns '.' is reserved."),
 	OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",

tools/perf/builtin-mem.c

@@ -286,7 +286,7 @@ int cmd_mem(int argc, const char **argv, const char *prefix __maybe_unused)
 		   "input file name"),
 	OPT_STRING('C', "cpu", &mem.cpu_list, "cpu",
 		   "list of cpus to profile"),
-	OPT_STRING('x', "field-separator", &symbol_conf.field_sep,
+	OPT_STRING_NOEMPTY('x', "field-separator", &symbol_conf.field_sep,
 		   "separator",
 		   "separator for columns, no spaces will be added"
 		   " between columns '.' is reserved."),