tree 6e1cd1fa67a812223cd79d7b61db066f7c7bb904
parent ce90da1d9665a3a284e492008db113b8d4d34df2
author Patrick Williams <patrick@stwcx.xyz> 1637354902 -0600
committer Patrick Williams <patrick@stwcx.xyz> 1637356820 -0600

slot: explicitly transfer pointer

The slot class is intended to be an RAII wrapper around the C-style
`sd_bus_slot*`.  As part of the constructor it gets the pointer it is
assuming ownership for.

The previous constructor took the `sd_bus_slot*` by value so it was
possible that the caller still kept the slot rather than fully
transferring ownership.  Switch the constructor to an r-value reference
so that the caller's pointer can be erased as part of the ownership
transfer.

Also, add an assignment operator to simplify the syntax when a slot is
first initialized with `nullptr` and then later given ownership of a
newly constructed slot.

While this is an incompatible constructor change, it is not expected to
affect any current users.  The only example of referencing a
`slot::slot` I could see in the current OpenBMC org calls the
constructor with a `nullptr`, which will seamlessly call the new r-value
variant.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I577de2e10e4d5ccae6337c763b848ea4cf2121dd