Remove use of rustc_attrs, which is no longer needed. (#53)

* Remove use of `rustc_attrs`, which is no longer needed.

This io-lifetimes crate no longer needs this rustc_attrs code. On Rust
versions where io_safety is stabilized, we use the version in std (which
uses rustc_attrs internally). On Rust versions where it's not, rustc_attrs
isn't available to user code anyway, since it's not a stable language
feature.

This might fix #51.

* Rename `io_lifetimes_use_std` to `io_safety_is_in_std`.

This may also help fix #51.

Cargo.toml

@@ -25,7 +25,7 @@ fs-err = { version = "2.6.0", optional = true }
 os_pipe = { version = "1.0.0", features = ["io_safety"], optional = true }
 
 # The following dependencies allow io-lifetimes to define impls for various
-# third-party traits. This is only done in not(io_lifetimes_use_std) mode,
+# third-party traits. This is only done in not(io_safety_is_in_std) mode,
 # because when we're using the std types and traits, we can't define impls
 # on third-party traits, due to the orphan rule. Work is ongoing to add
 # the needs impls upstream.

README.md

@@ -20,9 +20,6 @@ This is associated with [RFC 3128], the I/O Safety RFC, which is now merged.
 Work is now underway to move the `OwnedFd` and `BorrowedFd` types and `AsFd`
 trait developed here into `std`.
 
-Some features currently require nightly Rust, as they depend on `rustc_attrs`
-to perform niche optimizations needed for FFI use cases.
-
 For a quick taste, check out the code examples:
 
  - [hello], a basic demo of this API, doing low-level I/O manually, using the

build.rs

@@ -4,13 +4,9 @@ use std::io::Write;
 fn main() {
     // I/O safety is stabilized in Rust 1.63.
     if has_io_safety() {
-        use_feature("io_lifetimes_use_std")
+        use_feature("io_safety_is_in_std")
     }
 
-    // Niche optimizations for `Borrowed*` and `Owned*` depend on `rustc_attrs`
-    // which, outside of `std`, are only available on nightly.
-    use_feature_or_nothing("rustc_attrs");
-
     // Work around
     // https://github.com/rust-lang/rust/issues/103306.
     use_feature_or_nothing("wasi_ext");

examples/hello.rs

@@ -1,7 +1,7 @@
 //! A simple testcase that prints a few messages to the console, demonstrating
 //! the io-lifetimes API.
 
-#![cfg_attr(not(rustc_attrs), allow(unused_imports))]
+#![cfg_attr(not(io_safety_is_in_std), allow(unused_imports))]
 
 #[cfg(feature = "close")]
 use io_lifetimes::example_ffi::*;
@@ -14,12 +14,12 @@ use std::{
 #[cfg(all(unix, feature = "close"))]
 use io_lifetimes::{AsFd, OwnedFd};
 
-#[cfg(windows)]
-use io_lifetimes::{AsHandle, FromHandle, OwnedHandle};
-#[cfg(windows)]
+#[cfg(all(windows, feature = "close"))]
+use io_lifetimes::{AsHandle, OwnedHandle};
+#[cfg(all(windows, feature = "close"))]
 use std::{convert::TryInto, os::windows::io::RawHandle, ptr::null_mut};
 
-#[cfg(all(rustc_attrs, unix, feature = "close"))]
+#[cfg(all(io_safety_is_in_std, unix, feature = "close"))]
 fn main() -> io::Result<()> {
     let fd = unsafe {
         // Open a file, which returns an `Option<OwnedFd>`, which we can
@@ -120,9 +120,9 @@ fn main() -> io::Result<()> {
 }
 
 #[cfg(all(
-    not(all(rustc_attrs, unix, feature = "close")),
+    not(all(io_safety_is_in_std, unix, feature = "close")),
     not(all(windows, feature = "close"))
 ))]
 fn main() {
-    println!("On Unix, this example requires Rust nightly (for `rustc_attrs`) and the \"close\" feature.");
+    println!("On Unix, this example requires Rust nightly (for `io_safety_is_in_std`) and the \"close\" feature.");
 }

examples/owning-wrapper.rs

@@ -1,16 +1,16 @@
 //! A simple example implementing the main traits for a type.
 
 #[cfg(not(windows))]
-#[cfg(any(feature = "close", not(io_lifetimes_use_std)))]
+#[cfg(any(feature = "close", not(io_safety_is_in_std)))]
 use io_lifetimes::FromFd;
 #[cfg(windows)]
-#[cfg(any(feature = "close", not(io_lifetimes_use_std)))]
+#[cfg(any(feature = "close", not(io_safety_is_in_std)))]
 use io_lifetimes::FromHandle;
 #[cfg(not(windows))]
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 use io_lifetimes::IntoFd;
 #[cfg(windows)]
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 use io_lifetimes::IntoHandle;
 use io_lifetimes::OwnedFilelike;
 #[cfg(not(windows))]
@@ -43,7 +43,7 @@ impl AsFd for Thing {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(not(windows))]
 impl IntoFd for Thing {
     #[inline]
@@ -60,7 +60,7 @@ impl From<Thing> for OwnedFd {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(not(windows))]
 impl FromFd for Thing {
     #[inline]
@@ -85,7 +85,7 @@ impl AsHandle for Thing {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 impl IntoHandle for Thing {
     #[inline]
@@ -102,7 +102,7 @@ impl From<Thing> for OwnedHandle {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 impl FromHandle for Thing {
     #[inline]

src/example_ffi.rs

@@ -1,6 +1,6 @@
 //! This is just a sample of what FFI using this crate can look like.
 
-#![cfg_attr(not(rustc_attrs), allow(unused_imports))]
+#![cfg_attr(not(io_safety_is_in_std), allow(unused_imports))]
 #![allow(missing_docs)]
 
 #[cfg(any(unix, target_os = "wasi"))]
@@ -23,7 +23,7 @@ use {
 };
 
 // Declare a few FFI functions ourselves, to show off the FFI ergonomics.
-#[cfg(all(rustc_attrs, any(unix, target_os = "wasi")))]
+#[cfg(all(io_safety_is_in_std, any(unix, target_os = "wasi")))]
 extern "C" {
     pub fn open(pathname: *const c_char, flags: c_int, ...) -> Option<OwnedFd>;
 }

src/lib.rs

@@ -28,22 +28,21 @@
 //! [from+into conversions]: FromFilelike::from_into_filelike
 
 #![deny(missing_docs)]
-#![cfg_attr(rustc_attrs, feature(rustc_attrs))]
 // Work around https://github.com/rust-lang/rust/issues/103306.
 #![cfg_attr(all(wasi_ext, target_os = "wasi"), feature(wasi_ext))]
 
 mod portability;
 mod traits;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 mod types;
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 mod impls_std;
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(any(unix, target_os = "wasi"))]
 pub use traits::AsFd;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 pub use traits::{AsHandle, AsSocket};
 #[cfg(any(unix, target_os = "wasi"))]
@@ -53,23 +52,23 @@ pub use traits::{FromFd, IntoFd};
 #[allow(deprecated)]
 pub use traits::{FromHandle, FromSocket, IntoHandle, IntoSocket};
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(any(unix, target_os = "wasi"))]
 pub use types::{BorrowedFd, OwnedFd};
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 pub use types::{
     BorrowedHandle, BorrowedSocket, HandleOrInvalid, InvalidHandleError, NullHandleError,
     OwnedHandle, OwnedSocket,
 };
 
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(unix)]
 pub use std::os::unix::io::{AsFd, BorrowedFd, OwnedFd};
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(target_os = "wasi")]
 pub use std::os::wasi::io::{AsFd, BorrowedFd, OwnedFd};
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(windows)]
 pub use std::os::windows::io::{
     AsHandle, AsSocket, BorrowedHandle, BorrowedSocket, HandleOrInvalid, InvalidHandleError,
@@ -87,7 +86,7 @@ pub use std::os::windows::io::{
 //
 // So we define `FromFd`/`IntoFd` traits, and implement them in terms of
 // `From`/`Into`,
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(any(unix, target_os = "wasi"))]
 #[allow(deprecated)]
 impl<T: From<OwnedFd>> FromFd for T {
@@ -96,7 +95,7 @@ impl<T: From<OwnedFd>> FromFd for T {
         owned_fd.into()
     }
 }
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(any(unix, target_os = "wasi"))]
 #[allow(deprecated)]
 impl<T> IntoFd for T
@@ -109,7 +108,7 @@ where
     }
 }
 
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(windows)]
 #[allow(deprecated)]
 impl<T: From<OwnedHandle>> FromHandle for T {
@@ -118,7 +117,7 @@ impl<T: From<OwnedHandle>> FromHandle for T {
         owned_handle.into()
     }
 }
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(windows)]
 #[allow(deprecated)]
 impl<T> IntoHandle for T
@@ -131,7 +130,7 @@ where
     }
 }
 
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(windows)]
 #[allow(deprecated)]
 impl<T: From<OwnedSocket>> FromSocket for T {
@@ -140,7 +139,7 @@ impl<T: From<OwnedSocket>> FromSocket for T {
         owned_socket.into()
     }
 }
-#[cfg(io_lifetimes_use_std)]
+#[cfg(io_safety_is_in_std)]
 #[cfg(windows)]
 #[allow(deprecated)]
 impl<T> IntoSocket for T
@@ -165,22 +164,22 @@ pub mod views;
 
 // Ideally, we'd want crates to implement our traits themselves. But for now,
 // while we're prototyping, we provide a few impls on foreign types.
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(feature = "async-std")]
 mod impls_async_std;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(feature = "fs-err")]
 mod impls_fs_err;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(feature = "mio")]
 mod impls_mio;
 #[cfg(not(target_os = "wasi"))]
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(feature = "os_pipe")]
 mod impls_os_pipe;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(feature = "socket2")]
 mod impls_socket2;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(feature = "tokio")]
 mod impls_tokio;

src/traits.rs

@@ -1,9 +1,9 @@
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(any(unix, target_os = "wasi"))]
 use crate::BorrowedFd;
 #[cfg(any(unix, target_os = "wasi"))]
 use crate::OwnedFd;
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 use crate::{BorrowedHandle, BorrowedSocket};
 #[cfg(windows)]
@@ -14,7 +14,7 @@ use crate::{OwnedHandle, OwnedSocket};
 /// This is only available on unix platforms and must be imported in order to
 /// call the method. Windows platforms have a corresponding `AsHandle` and
 /// `AsSocket` set of traits.
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(any(unix, target_os = "wasi"))]
 pub trait AsFd {
     /// Borrows the file descriptor.
@@ -34,7 +34,7 @@ pub trait AsFd {
 }
 
 /// A trait to borrow the handle from an underlying object.
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 pub trait AsHandle {
     /// Borrows the handle.
@@ -54,7 +54,7 @@ pub trait AsHandle {
 }
 
 /// A trait to borrow the socket from an underlying object.
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 pub trait AsSocket {
     /// Borrows the socket.
@@ -235,7 +235,7 @@ pub trait FromSocket {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(any(unix, target_os = "wasi"))]
 impl<T: AsFd> AsFd for &T {
     #[inline]
@@ -244,7 +244,7 @@ impl<T: AsFd> AsFd for &T {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(any(unix, target_os = "wasi"))]
 impl<T: AsFd> AsFd for &mut T {
     #[inline]
@@ -253,7 +253,7 @@ impl<T: AsFd> AsFd for &mut T {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 impl<T: AsHandle> AsHandle for &T {
     #[inline]
@@ -262,7 +262,7 @@ impl<T: AsHandle> AsHandle for &T {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 impl<T: AsHandle> AsHandle for &mut T {
     #[inline]
@@ -271,7 +271,7 @@ impl<T: AsHandle> AsHandle for &mut T {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 impl<T: AsSocket> AsSocket for &T {
     #[inline]
@@ -280,7 +280,7 @@ impl<T: AsSocket> AsSocket for &T {
     }
 }
 
-#[cfg(not(io_lifetimes_use_std))]
+#[cfg(not(io_safety_is_in_std))]
 #[cfg(windows)]
 impl<T: AsSocket> AsSocket for &mut T {
     #[inline]

src/types.rs

@@ -50,12 +50,6 @@ const INVALID_SOCKET: usize = !0 as _;
 #[cfg(any(unix, target_os = "wasi"))]
 #[derive(Copy, Clone)]
 #[repr(transparent)]
-#[cfg_attr(rustc_attrs, rustc_nonnull_optimization_guaranteed)]
-#[cfg_attr(rustc_attrs, rustc_layout_scalar_valid_range_start(0))]
-// libstd/os/raw/mod.rs assures me that every libstd-supported platform has a
-// 32-bit c_int. Below is -2, in two's complement, but that only works out
-// because c_int is 32 bits.
-#[cfg_attr(rustc_attrs, rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE))]
 pub struct BorrowedFd<'fd> {
     fd: RawFd,
     _phantom: PhantomData<&'fd OwnedFd>,
@@ -105,17 +99,6 @@ pub struct BorrowedHandle<'handle> {
 #[cfg(windows)]
 #[derive(Copy, Clone)]
 #[repr(transparent)]
-#[cfg_attr(rustc_attrs, rustc_nonnull_optimization_guaranteed)]
-#[cfg_attr(rustc_attrs, rustc_layout_scalar_valid_range_start(0))]
-// This is -2, in two's complement. -1 is `INVALID_SOCKET`.
-#[cfg_attr(
-    all(rustc_attrs, target_pointer_width = "32"),
-    rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)
-)]
-#[cfg_attr(
-    all(rustc_attrs, target_pointer_width = "64"),
-    rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FF_FF_FF_FF_FE)
-)]
 pub struct BorrowedSocket<'socket> {
     socket: RawSocket,
     _phantom: PhantomData<&'socket OwnedSocket>,
@@ -131,12 +114,6 @@ pub struct BorrowedSocket<'socket> {
 /// has the value `-1`.
 #[cfg(any(unix, target_os = "wasi"))]
 #[repr(transparent)]
-#[cfg_attr(rustc_attrs, rustc_nonnull_optimization_guaranteed)]
-#[cfg_attr(rustc_attrs, rustc_layout_scalar_valid_range_start(0))]
-// libstd/os/raw/mod.rs assures me that every libstd-supported platform has a
-// 32-bit c_int. Below is -2, in two's complement, but that only works out
-// because c_int is 32 bits.
-#[cfg_attr(rustc_attrs, rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE))]
 pub struct OwnedFd {
     fd: RawFd,
 }
@@ -286,17 +263,6 @@ impl BorrowedHandle<'_> {
 /// [`INVALID_SOCKET`].
 #[cfg(windows)]
 #[repr(transparent)]
-#[cfg_attr(rustc_attrs, rustc_nonnull_optimization_guaranteed)]
-#[cfg_attr(rustc_attrs, rustc_layout_scalar_valid_range_start(0))]
-// This is -2, in two's complement. -1 is `INVALID_SOCKET`.
-#[cfg_attr(
-    all(rustc_attrs, target_pointer_width = "32"),
-    rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)
-)]
-#[cfg_attr(
-    all(rustc_attrs, target_pointer_width = "64"),
-    rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FF_FF_FF_FF_FE)
-)]
 pub struct OwnedSocket {
     socket: RawSocket,
 }

tests/ffi.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(not(rustc_attrs), allow(unused_imports))]
+#![cfg_attr(not(io_safety_is_in_std), allow(unused_imports))]
 #![cfg(feature = "close")]
 
 #[cfg(any(unix, windows))]
@@ -12,7 +12,7 @@ use windows_sys::Win32::Storage::FileSystem::{
     FILE_ATTRIBUTE_NORMAL, FILE_GENERIC_READ, OPEN_EXISTING,
 };
 
-#[cfg(all(rustc_attrs, unix))]
+#[cfg(all(io_safety_is_in_std, unix))]
 #[test]
 fn test_file_not_found() {
     assert!(unsafe {
@@ -50,7 +50,7 @@ fn test_file_not_found() {
     );
 }
 
-#[cfg(all(rustc_attrs, unix))]
+#[cfg(all(io_safety_is_in_std, unix))]
 #[test]
 fn test_file_found() {
     assert!(unsafe { open("Cargo.toml\0".as_ptr() as *const _, O_RDONLY | O_CLOEXEC) }.is_some());

tests/niche-optimizations.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(not(rustc_attrs), allow(unused_imports))]
+#![cfg_attr(not(io_safety_is_in_std), allow(unused_imports))]
 #![cfg_attr(target_os = "wasi", feature(wasi_ext))]
 
 use std::mem::size_of;
@@ -15,7 +15,7 @@ use std::os::wasi::io::{FromRawFd, IntoRawFd, RawFd};
 #[cfg(windows)]
 use std::os::windows::io::{FromRawSocket, IntoRawSocket, RawSocket};
 
-#[cfg(all(rustc_attrs, any(unix, target_os = "wasi")))]
+#[cfg(all(io_safety_is_in_std, any(unix, target_os = "wasi")))]
 #[test]
 fn test_niche_optimizations() {
     assert_eq!(size_of::<Option<OwnedFd>>(), size_of::<RawFd>());
@@ -38,7 +38,7 @@ fn test_niche_optimizations() {
     }
 }
 
-#[cfg(all(rustc_attrs, windows))]
+#[cfg(all(io_safety_is_in_std, windows))]
 #[test]
 fn test_niche_optimizations_socket() {
     assert_eq!(size_of::<Option<OwnedSocket>>(), size_of::<RawSocket>());