The C-client library will crash when invoking the asynchronous zoo_aremove_watchers() API function with the 'local' argument set to 1.
The reason is: if the local argument is 1/true, then the code does 'notify_sync_completion((struct sync_completion *)data);' But casting the 'data' variable to a sync_completion struct pointer is bogus/invalid, and when it's later handles as that struct pointer it's accessing invalid memory.
As a side note: it will work ok when called synchronously through zoo_remove_watchers(), because that function creates a sync_completion struct and passes it to the asynch zoo_aremove_watchers(), but it will not work ok when the asynch function is used directly for the reason stated perviously.
Another side note: the docs state that setting the 'local' flag makes the C-client remove the watcher "even if there is no server connection" - but really it makes the C-client remove the watcher without notifying the server at all, even if the connection to a server is up. (well... that's what it would do if it didn't just crash instead