Rust 1.38.0

Language

• The #[global_allocator] attribute can now be used in submodules.
• The #[deprecated] attribute can now be used on macros.

Compiler

• Added pipelined compilation support to rustc. This will improve compilation times in some cases. For further information please refer to the "Evaluating pipelined rustc compilation" thread.
• Added tier 3* support for the aarch64-uwp-windows-msvc, i686-uwp-windows-gnu, i686-uwp-windows-msvc, x86_64-uwp-windows-gnu, and x86_64-uwp-windows-msvc targets.
• Added tier 3 support for the armv7-unknown-linux-gnueabi and armv7-unknown-linux-musleabi targets.
• Added tier 3 support for the hexagon-unknown-linux-musl target.
• Added tier 3 support for the riscv32i-unknown-none-elf target.
• Upgraded to LLVM 9.

* Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• ascii::EscapeDefault now implements Clone and Display.
• Derive macros for prelude traits (e.g. Clone, Debug, Hash) are now available at the same path as the trait. (e.g. The Clone derive macro is available at std::clone::Clone). This also makes all built-in macros available in std/core root. e.g. std::include_bytes!.
• str::Chars now implements Debug.
• slice::{concat, connect, join} now accepts &[T] in addition to &T.
• *const T and *mut T now implement marker::Unpin.
• Arc<[T]> and Rc<[T]> now implement FromIterator<T>.
• Added euclidean remainder and division operations (div_euclid, rem_euclid) to all numeric primitives. Additionally checked, overflowing, and wrapping versions are available for all integer primitives.
• thread::AccessError now implements Clone, Copy, Eq, Error, and PartialEq.
• iter::{StepBy, Peekable, Take} now implement DoubleEndedIterator.

Stabilized APIs

• <*const T>::cast
• <*mut T>::cast
• Duration::as_secs_f32
• Duration::as_secs_f64
• Duration::div_f32
• Duration::div_f64
• Duration::from_secs_f32
• Duration::from_secs_f64
• Duration::mul_f32
• Duration::mul_f64
• any::type_name

Cargo

• Added pipelined compilation support to cargo.
• You can now pass the --features option multiple times to enable multiple features.

Rustdoc

• Documentation on pub use statements is prepended to the documentation of the re-exported item

Misc

• rustc will now warn about some incorrect uses of mem::{uninitialized, zeroed} that are known to cause undefined behaviour.

Compatibility Notes

• The x86_64-unknown-uefi platform can not be built with rustc 1.38.0.
• The armv7-unknown-linux-gnueabihf platform is known to have issues with certain crates such as libc.