Hello and welcome to the tenth issue of This Week in Rust. This week marks the enabling of the new runtime written entirely in Rust. A lot happens every week, so I'm going to start omitting PRs that I deem of lesser importance. This process is entirely arbitrary, don't feel hurt if I exclude your PR :).

What's cooking on master?

Issue churn was -12 this week. A total of 70 PRs were merged.

The new runtime has been enabled by default. This is the culmination of a lot of work by brson and the rt interns (toddaaro, bblum, and ecr being the ones I know of). It's written entirely in Rust, and lives in std::rt. Additionally, the old C++ runtime has been removed.

Breaking Changes

• Trailing nulls have been removed from all string types.. This will break your FFI code in subtle and mysterious ways, if you didn't explicitly use the as_c_str methods. FFI code using the new str::c_str code will be more robust, as it forbids interior nulls, and ensures that a trailing null always exists. The replacement for str.as_c_str is str.to_c_str().as_slice(), from what I can tell.
• The priv keyword is no longer allowed where it has no meaning.
• iter and iter_err in Result have been replaced with external iterators.
• The get method of Option, Either, and Result has been removed in favor of unwrap. They both did the same thing, which was useless duplication.
• std::gc and std::stackwalk have been removed, as they are obsolete with the new runtime.
• The transitionary foreach has been removed.

Notable library additions, bugfixes, and cleanup

• Some redundant Ord methods were removed from impls where the default methods sufficed.
• FromStr for IpAddr and SocketAddr is implemented.
• Work steealing is implemented for the newrt scheduler.
• A frequency counting function has been added to extra::stat.
• Saturating math is now implemented. I knew this as "clamping": it is arithmetic that clamps results into a specific interval.
• A hexadecimal encoding module has been added to extra.
• EnumSet has been moved into extra, it previously existed as a utility in rustc
• str::is_utf8 has seen some more optimization.

Notable compiler additions, bugfixes, and cleanup

• Initial support for the new formatting code has been added.
• A no_main attribute has been added, to omit the Rust entry point entirely.
• Vanilla Linux on ARM is now supported.
• Extra copies of rvalues are no longer omitted.
• Some cross-arch bugs with node hash metadata have been fixed.
• A soundness bug in struct matching has been fixed.
• An option_env! syntax extension has been added for compile-time inclusion of environment variables that may or may not be present.
• extern mod a = "b/c/d" has been implemented, paving the way for more rustpkg awesomeness.

Meetings

The Tuesday meeting seems to have been a bit under-attended. SIMD, ARM, trailing nulls, order of mod and use, and the condition system were all briefly discussed..

Discussion + Blog posts

• "A Work-stealing Runtime for Rust", toddaaro's intern presentation.
• "Iterator Blocks for Rust - Feature Survey"

External projects

• Galvanized: a simple JIT VM written in Rust, using LibJIT
• Q3 has a new logger. I think it's nicer than the built-in one!
• rust-protobuf: a protobuf implementation generating rust code, written in rust.
• Servo: almost passing acid1 !