GCC Rust Weekly Status Report 24

Thanks again to Open Source Security, inc and Embecosm for their ongoing support for this project.

Milestone Progress

We are getting closer to the end of this milestone and last week saw my long living branch finally getting merged. This branch has added the relevant code to support type bounds, which is the last building block to implement the remaining tasks of the traits milestone. This means future work to complete traits should be smaller and easier to review. However, two outstanding tasks carry some risk in making my deadline go over: trait objects (dyn keyword), which implements vtable lookups and autodref to resolve paths fully.

BCS and Rust London

I will be attending and speaking at a hybrid conference on the 25th August here is the relevant link if you wish to check in on this.

An evening with the London RUST Group

Monthly Community Call

We had our Monthly community call please find our meeting notes over on: https://github.com/Rust-GCC/Reporting/blob/main/2021-08-06-community-call.md

Detailed changelog

Type Bounds

Last week the goal was to finally merge last big branch which adds the initial type-bounds support such as:

trait Foo {
    fn default() -> i32;
    fn get(self) -> i32;
}

struct Bar(i32);
impl Foo for Bar {
    fn default() -> i32 {
        123
    }

    fn get(self) -> i32 {
        self.0
    }
}

fn type_bound_test<T: Foo>(a: T) -> i32 {
    T::default() + a.get()
}

fn main() {
    let a;
    a = Bar(456);

    let b;
    b = type_bound_test(a);
}

This includes checks for when a type does not support the type bound for example:

trait Foo {
    fn default() -> i32;
}

trait Bar {
    fn not_default() -> i32;
}

trait Baz {
    fn cake() -> i32;
}

struct Test(i32);

impl Foo for Test {
    fn default() -> i32 {
        1234
    }
}

fn type_bound_test<T: Foo + Bar + Baz>() -> i32 {
    T::default()
}

fn main() {
    let a = type_bound_test::<Test>();
}

Will return:

test.rs:26:31: error: bounds not satisfied for Test ‘Bar, Baz’ is not satisfied
   21 | fn type_bound_test<T: Foo + Bar + Baz>() -> i32 {
      |                             ~     ~
......
   26 |     let a = type_bound_test::<Test>();
      |                               ^

You watch some of the development process on my youtube channel for this patch:

Fix ICE when using f64 on 32 bit systems

Thanks to our new contributor Michael Karcher who has fixed an bug with how 64bit floats were handled on 32bit systems. GCC was automatically changing our f64 into float:80 which is the case when we need an excess precision type. The issue was that we were missing a gcc conversion for the new tree so the types are updated correctly.

This means we now have fully passing builds on Marks build farm:

debian arm64
fedora ppc64le
fedora ppc64
debian i386
fedora s390x

Thanks to John Paul Adrian Glaubitz who has also completed the manual testing on:

debian hppa
debian m68k
debian s390x

As part of GitHub automation we do not accept any PR which causes any regression to ubuntu-x86_64.

Fix parser bug when using null terminator in strings

With our recent examples showing HelloWorld working via printf, we noticed that the null terminator was not being respected when added to strings, this turned out to be a bug in the parser so we have added a new test case to catch this:

/* { dg-output "bar foo baz foobar\n" } */
extern "C"
{Last Week
  fn printf(s: *const i8, ...);
  fn memchr(s: *const i8, c: u8, n: usize) -> *const i8;
}

pub fn main ()
{
  let f = "%s %s %s %s\n\0";
  let s = "bar\0\
           foo\
           \x00\
           baz\u{0000}\
           foobar\0";
  let cf = f as *const str as *const i8;
  let cs = s as *const str as *const i8;
  unsafe
    {
      let cs2 = memchr (cs, b'f', 5);
      let cs3 = memchr (cs2, b'b', 5);
      let cs4 = memchr (cs3, b'f', 5);
      printf (cf, cs, cs2, cs3, cs4);
    }
}

Completed Activities

Typebounds support PR611 PR612
Fix lexer bug with nul terminated strings PR615
Union support PR601 PR602
Handle unsafe in liveness analysis PR604
Fix floating point issues with f64 on 32 bit systems PR614
Building blocks for multiple file support PR608 PR605
Fix ICE in parser when identifier is nullptr PR606
Cleanup PR612 PR610 PR607

Contributors this week

Excluding merges, 5 authors have pushed 25 commits to master and 26 commits to all branches. On master, 56 files have changed and there have been 1,799 additions and 775 deletions.

Overall Task Status

Category	Last Week	This Week	Delta
TODO	83	82	-1
In Progress	9	9	–
Completed	177	180	+3

GitHub Issues

Test Cases

Category	Last Week	This Week	Delta
Passing	3629	3766	+137
XFAIL	14	21	+7

make check-rust

Bugs

Category	Last Week	This Week	Delta
TODO	19	17	-2
In Progress	3	4	+1
Completed	59	61	+2

GitHub Bugs

Milestones Progress

Milestone	Last Week	This Week	Delta	Start Date	Completion Date	Target
Data Structures 1 – Core	100%	100%	–	30th Nov 2020	27th Jan 2021	29th Jan 2021
Control Flow 1 – Core	100%	100%	–	28th Jan 2021	10th Feb 2021	26th Feb 2021
Data Structures 2 – Generics	100%	100%	–	11th Feb 2021	14th May 2021	28th May 2021
Data Structures 3 – Traits	80%	83%	+3%	20th May 2021	–	27th Aug 2021
Control Flow 2 – Pattern Matching	0%	0%	–	–	–	29th Oct 2021
Imports and Visibility	0%	0%	–	–	–	TBD
Macros and cfg expansion	0%	0%	–	–	–	TBD
Const Generics	0%	0%	–	–	–	TBD
Intrinsics	0%	0%	–	–	–	TBD

GitHub Milestones

Planned Activities

Complete TypeBounds checks
Merge missing test cases for casts and coercions

YouTube

You can also watch me present this on youtube: