Workaround for https://github.com/apple/swift/issues/73532 #4951
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Increase the initial size of __CFReadSocketsFds to reduce the chance of resizing it which appears to lead to compiler hangs.
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CC @compnerd |
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Context: we are experiencing a occasional swift compiler hang issue on Windows on many-core machines. We have so far narrowed it down to dropped socket file descriptors due to some sort of data corruption in the The details are described at swiftlang/swift#73532 |
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The issue that @lxbndr pointed to in this comment means that the CFSocket code is mixing up its handling of fd_set on Windows:
- Platform macros FD_SET and FD_ISSET will know that
fd_setis a struct on Windows, - CFSocket code will assume it is a bitset for resizing purposes.
The change here will create an allocation big enough so that the CFSocket bitlogic doesn't think it has to resize the allocation, but it will still be doing incorrect bit-level logic on the fd_set. I think we should build on @lxbndr's suggested fix. It would help to avoid defining fd_mask on Windows at all to find the places where we are treating an fd_set as a bitfield.
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Closing in favor of #4954 |
Increase the initial size of __CFReadSocketsFds to reduce the chance of resizing it which appears to lead to compiler hangs.