[sheepdog] [PATCH 3/3] journal: use BUILD_BUG_ON() for checking the size of struct journal_descriptor

[Hitoshi Mitake]

This patch adds BUILD_BUG_ON() for checking the size of struct
journal_descriptor. Even if the struct modified in wrong manners, the
BUILD_BUG_ON() can detect the invalid changes (on the size).

Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
---
 sheep/journal.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sheep/journal.c b/sheep/journal.c
index 9ca1ce6..23a0ab7 100644
--- a/sheep/journal.c
+++ b/sheep/journal.c
@@ -437,3 +437,9 @@ int journal_write_epoch(const char *buf, size_t size, uint32_t epoch)
 	jd.epoch = epoch;
 	return journal_file_write(&jd, buf);
 }
+
+static __attribute__((used)) void journal_c_build_bug_ons(void)
+{
+	/* never called, only for checking BUILD_BUG_ON()s */
+	BUILD_BUG_ON(sizeof(struct journal_descriptor) != JOURNAL_DESC_SIZE);
+}
-- 
1.7.10.rc0.41.gfa678