Hi all,
I’m working on a networking API using multi handles and multi sockets, and
using libdispatch (GCD) to monitor socket changes (via the "dispatch source"
API [1]).
When receiving CURL_POLL_REMOVE, I call dispatch_source_cancel() [2] to stop
the dispatch source. As this is done asynchronously, it is required to wait for
the cancellation handler before closing the socket according to the
documentation:
> The cancellation handler is submitted to the source's target queue when the
> source's event handler has finished, indicating that it is safe to close the
> source's handle (file descriptor or mach port).
However libcurl closes the socket immediately after calling the socket
function, and at least on Windows this causes GCD to sometimes crash because
WSAEventSelect() returns WSAENOTSOCK ("Socket operation on nonsocket") here:
[3].
Does anyone have a suggestion as to how to work around this? The only thing I
can think of is to use CURLOPT_CLOSESOCKETFUNCTION and wait for the
cancellation handler before closing the socket. Would this be the recommended
approach? I’m fairly new to this topic, so I might be missing something obvious.
I found that building libcurl with "CURL_DISABLE_SOCKETPAIR" fixes most these
crashes, but this seems like a poor workaround and some crashes remain.
Thanks!
Frederik
[1]
https://developer.apple.com/documentation/dispatch/dispatch_source?language=objc
[2]
https://developer.apple.com/documentation/dispatch/1385604-dispatch_source_cancel?language=objc
[3]
https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/event/event_windows.c#L214-L223
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