Provide optional `Read`/`Write` methods for stdio
Override more of the default methods for `io::Read` and `io::Write` for stdio types, when efficient to do so, and deduplicate unsupported types.
Tracked in https://github.com/rust-lang/rust/issues/136756.
try-job: x86_64-msvc-1
Match what `std::io::Empty` does, since it is very similar. However,
still evaluate the `fmt::Arguments` in `write_fmt` to be consistent with
other platforms.
Implement `read_buf` for Hermit
Following https://github.com/hermit-os/kernel/pull/1606, it is now safe to implement `Read::read_buf` for file descriptors on Hermit.
cc ```@mkroening```
Implement `read_buf` and vectored read/write for SGX stdio
Implement `read_buf`, `read_vectored`, and `write_vectored` for the SGX stdio types.
Additionally, extend `User<T>::copy_to_enclave` to work for copying to uninitialized values and fix unsoundness in `UserRef<[T]>::copy_to_enclave_vec`.
cc ``@jethrogb``
Tracked in https://github.com/rust-lang/rust/issues/136756
As per #117276, this moves the platform definitions of `Stdout` and friends into `sys`. This PR also unifies the UNIX and Hermit implementations and moves the `__rust_print_err` function needed by libunwind on SGX into the dedicated module for such helper functions.
