The documentation for RtlNtStatusToDosError explicitly tells to call
it via GetProcAddress. The documentation for NtQueryInformationFile
does not, but similar considerations apply because there is normally
no import library for ntdll.
The main reason to use GetProcAddress though is because MinGW does
include an import library for ntdll, this import library contains
a definition of setjmp, and because of the way rustc orders linker
arguments, this definition of setjmp conflicts with and gets picked
over the one in msvcrt. Using setjmp from ntdll is undesirable as it
is an undocumented API and it is missing from wine, making it harder
to develop wasmtime using a cross-compiler.
Fixes#1738.
This commit fully implements `__wasi_fd_fdstat_get` on Windows so that
the descriptor flags can be determined.
It does this by calling into `NtQueryInformationFile` (safe to call from
user mode) to get the open mode and access of the underlying OS handle.
`NtQueryInformationFile` isn't included in the `winapi` crate, so it is
manually being linked against.
This commit also fixes several bugs on Windows:
* Ignore `__WASI_FDFLAG_NONBLOCK` by not setting `FILE_FLAG_OVERLAPPED`
on file handles (the POSIX behavior for `O_NONBLOCK` on files).
* Use `FILE_FLAG_WRITE_THROUGH` for the `__WASI_FDFLAG_?SYNC` flags.
* `__WASI_FDFLAG_APPEND` should disallow `FILE_WRITE_DATA` access to
force append-only on write operations.
* Use `GENERIC_READ` and `GENERIC_WRITE` access flags. The
latter is required when opening a file for truncation.
