lockable: add QEMU_MAKE_LOCKABLE_NONNULL

This will be needed for lock guards, because if the lock is NULL the
dummy for loop of the lock guard never runs.  This can cause confusion
and dummy warnings in the compiler, but even if it did not, aborting
with a NULL pointer dereference is a less surprising behavior.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/include/qemu/lockable.h b/include/qemu/lockable.h
index 84ea794..313d4d9 100644 (file)
--- a/include/qemu/lockable.h
+++ b/include/qemu/lockable.h
@@ -65,7 +65,7 @@ qemu_make_lockable(void *x, QemuLockable *lockable)
  * In C++ it would be different, but then C++ wouldn't need QemuLockable
  * either...
  */
-#define QEMU_MAKE_LOCKABLE_(x) qemu_make_lockable((x), &(QemuLockable) {    \
+#define QEMU_MAKE_LOCKABLE_(x) (&(QemuLockable) {     \
         .object = (x),                               \
         .lock = QEMU_LOCK_FUNC(x),                   \
         .unlock = QEMU_UNLOCK_FUNC(x),               \
@@ -76,11 +76,24 @@ qemu_make_lockable(void *x, QemuLockable *lockable)
  * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
  *
  * Returns a QemuLockable object that can be passed around
- * to a function that can operate with locks of any kind.
+ * to a function that can operate with locks of any kind, or
+ * NULL if @x is %NULL.
  */
 #define QEMU_MAKE_LOCKABLE(x)                        \
     QEMU_GENERIC(x,                                  \
                  (QemuLockable *, (x)),              \
+                 qemu_make_lockable((x), QEMU_MAKE_LOCKABLE_(x)))
+
+/* QEMU_MAKE_LOCKABLE_NONNULL - Make a polymorphic QemuLockable
+ *
+ * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
+ *
+ * Returns a QemuLockable object that can be passed around
+ * to a function that can operate with locks of any kind.
+ */
+#define QEMU_MAKE_LOCKABLE_NONNULL(x)                \
+    QEMU_GENERIC(x,                                  \
+                 (QemuLockable *, (x)),              \
                  QEMU_MAKE_LOCKABLE_(x))
 
 static inline void qemu_lockable_lock(QemuLockable *x)