Hadriel Kaplan created ZOOKEEPER-2320:
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Summary: C-client crashes when removing watcher asynchronously in
"local" mode
Key: ZOOKEEPER-2320
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2320
Project: ZooKeeper
Issue Type: Bug
Components: c client
Affects Versions: 3.5.1
Reporter: Hadriel Kaplan
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 ;)
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