When shutting down helper processes, PosixSocketHelper::close() in
SocketWindows when trying to close the socket fd with
WSANOTINITIALISED. This was due to us initiating WinSock2 during static
initialization and presumably also not terminating WinSock2 properly.
Similar to WinSock2 initiation, calling CRT during static
initialization is considered dangerous given the CRT DLL itself may not
yet be initialized.
Because of the above, we move to perform this Windows-specific
runtime setup/teardown calls into the main() functions.
This uses splice on Linux and mmap+write elsewhere to transfer a file to
a pipe. Note we cannot use sendfile because (at least on macOS) the
receiving fd must be a socket.
There is no direct Win32 API equivalent, but calling WM_CLOSE on
the top-level windows allows for a graceful shutdown where resources
are able to clean themselves up properly
This is a remnant from SerenityOS. Let's avoid confusion as to why we
negate errno when we call Error::from_syscall just to negate it again
when we store the error code.
_O_OBTAIN_DIR flag makes _open use FILE_FLAG_BACKUP_SEMANTICS in
CreateFile call.
FILE_FLAG_BACKUP_SEMANTICS is required to open directory handles.
For ordinary files FILE_FLAG_BACKUP_SEMANTICS overrides file security
checks when the process has SE_BACKUP_NAME and SE_RESTORE_NAME
privileges, see https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
