[llvm] [llvm][Support] ListeningSocket::accept returns operation_canceled if FD is set to -1 (PR #89479)

[Michael Spencer via llvm-commits]

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@@ -200,35 +200,40 @@ ListeningSocket::accept(std::chrono::milliseconds Timeout) {
   while (PollStatus == -1 && (Timeout.count() == -1 || ElapsedTime < Timeout)) {
     if (Timeout.count() != -1)
       RemainingTime -= ElapsedTime.count();
-
     auto Start = std::chrono::steady_clock::now();
+
 #ifdef _WIN32
     PollStatus = WSAPoll(FDs, 2, RemainingTime);
-    if (PollStatus == SOCKET_ERROR) {
 #else
     PollStatus = ::poll(FDs, 2, RemainingTime);
+#endif
+    // If FD equals -1 then ListeningSocket::shutdown has been called and it is
+    // appropriate to return operation_canceled. ListeningSocket::shutdown
+    // copies FD's value to ObservedFD then sets FD to -1 before canceling
+    // ::poll by calling close on ObservedFD and writing to the pipe.
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Bigcheese wrote:

Don't really need the second sentence here, people can go look at the implementation to see why the first sentence is true.

https://github.com/llvm/llvm-project/pull/89479