journald: properly update message size after stripping the identifier

Valgrind says:
==29176== Conditional jump or move depends on uninitialised value(s)
==29176==    at 0x412A85: cunescape_length_with_prefix (util.c:1565)
==29176==    by 0x40B351: dev_kmsg_record (journald-kmsg.c:301)
==29176==    by 0x40B653: server_read_dev_kmsg (journald-kmsg.c:347)
==29176==    by 0x40B701: server_flush_dev_kmsg (journald-kmsg.c:365)
==29176==    by 0x409DE7: main (journald.c:1535)

1 files changed, 44 insertions, 0 deletions

diff --git a/src/journal/test-journal-syslog.c b/src/journal/test-journal-syslog.c
new file mode 100644
index 0000000000..3ae8633f22
--- /dev/null
+++ b/src/journal/test-journal-syslog.c
@@ -0,0 +1,44 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2011 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "journald-syslog.h"
+#include "macro.h"
+
+static void test_syslog_parse_identifier(const char* str,
+                                         const char *ident, const char*pid, int ret) {
+        const char *buf = str;
+        char *ident2 = NULL, *pid2 = NULL;
+        int ret2;
+
+        ret2 = syslog_parse_identifier(&buf, &ident2, &pid2);
+
+        assert(ret == ret2);
+        assert(ident==ident2 || !strcmp(ident, ident2));
+        assert(pid==pid2 || !strcmp(pid, pid2));
+}
+
+int main(void) {
+        test_syslog_parse_identifier("pidu[111]: xxx", "pidu", "111", 11);
+        test_syslog_parse_identifier("pidu: xxx", "pidu", NULL, 6);
+        test_syslog_parse_identifier("pidu xxx", NULL, NULL, 0);
+
+        return 0;
+}