Fix two problems regarding fork() and async IO for Windows #1431
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The duplicated handles in DeduplicateStdioHandles() should be inheritable. Otherwise sys_fork_nt_parent() will pass non-inheritable handles to CreateProcess().
Even given OVERLAPPED, functions like ReadFile/WriteFile still MAY complete before they return. In that case, we should not call GetOverlappedResult, and should respect the numberOfBytes output from the original IO function.
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p.s. This PR fixes #913 |
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1.
DeduplicateStdioHandles()should mark the new handles inheritablesys_fork_nt_parent() is directly passing std handles to child process. It would be a problem if those handles are non-inheritable.
2. Async IO on Windows might be synchronous
Even if the
OVERLAPPEDparameter supplied, IO functions likeReadFile/WriteFilemay still complete their jobs before they return. In that case, thenumberOfBytesresult from the IO functions should be respected, andGetOverlappedResultshould not be called.WriteFile
Asynchronous disk I/O appears as synchronous on Windows