[Libguestfs] [RFC: nbdkit PATCH] cleanup: Assert mutex sanity

[Eric Blake]

Although we haven't always checked that pthread_mutex_[un]lock
succeeded, it never hurts to avoid blatant programming bugs such as
when EINVAL can detect use of an uninitialized mutex.

Signed-off-by: Eric Blake <eblake at redhat.com>
---

Applies on top of my series to move cleanup.c to common/

Should I also go through and add checking to other bare
pthread_mutex_[un]lock() calls?

 common/utils/cleanup.h | 5 ++++-
 common/utils/cleanup.c | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/common/utils/cleanup.h b/common/utils/cleanup.h
index e6e6140..0ab9e65 100644
--- a/common/utils/cleanup.h
+++ b/common/utils/cleanup.h
@@ -43,6 +43,9 @@ extern void cleanup_unlock (pthread_mutex_t **ptr);
 #define CLEANUP_UNLOCK __attribute__((cleanup (cleanup_unlock)))
 #define ACQUIRE_LOCK_FOR_CURRENT_SCOPE(mutex) \
   CLEANUP_UNLOCK pthread_mutex_t *_lock = mutex; \
-  pthread_mutex_lock (_lock)
+  do { \
+    int _r = pthread_mutex_lock (_lock); \
+    assert (!_r); \
+  } while (0)

 #endif /* NBDKIT_CLEANUP_H */
diff --git a/common/utils/cleanup.c b/common/utils/cleanup.c
index 196d910..995f46c 100644
--- a/common/utils/cleanup.c
+++ b/common/utils/cleanup.c
@@ -53,5 +53,6 @@ cleanup_extents_free (void *ptr)
 void
 cleanup_unlock (pthread_mutex_t **ptr)
 {
-  pthread_mutex_unlock (*ptr);
+  int r = pthread_mutex_unlock (*ptr);
+  assert (!r);
 }
-- 
2.20.1