IoSlice/IoSliceMut should be Send and Sync

[withoutboats]

Closes #70308

[rust-highfive]

r? @Mark-Simulacrum

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[Mark-Simulacrum]

Hm, I wonder if this is the right approach - I would personally prefer to add them to each sys module where it's easier to audit (particularly when adding new things). What do you think about that? (Obviously more work)

(Sorry about closing/opening, misclicked)

[sfackler]

I think adding them at the top level is the right way to go - we're going to inevitably have this problem on random obscure targets going forward otherwise. The types are semantically just byte slices, so I can't imagine there would exist a platform that could possibly need to not have these impls.

[rust-highfive]

The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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2020-03-23T23:42:56.2541955Z ========================== Starting Command Output ===========================
2020-03-23T23:42:56.2544593Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/a78bfe7c-d650-475f-83c0-856f635db2b1.sh
2020-03-23T23:42:56.2544836Z 
2020-03-23T23:42:56.2548909Z ##[section]Finishing: Disable git automatic line ending conversion
2020-03-23T23:42:56.2566874Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70342/merge to s
2020-03-23T23:42:56.2571485Z Task         : Get sources
2020-03-23T23:42:56.2571774Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-23T23:42:56.2572051Z Version      : 1.0.0
2020-03-23T23:42:56.2572252Z Author       : Microsoft
---
2020-03-23T23:42:57.2428455Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-03-23T23:42:57.2433961Z ##[command]git config gc.auto 0
2020-03-23T23:42:57.2437648Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-03-23T23:42:57.2441067Z ##[command]git config --get-all http.proxy
2020-03-23T23:42:57.2447161Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/70342/merge:refs/remotes/pull/70342/merge
---
2020-03-23T23:51:28.7511131Z configure: build.locked-deps    := True
2020-03-23T23:51:28.7511424Z configure: llvm.ccache          := sccache
2020-03-23T23:51:28.7511918Z configure: build.cargo-native-static := True
2020-03-23T23:51:28.7512380Z configure: dist.missing-tools   := True
2020-03-23T23:51:28.7512967Z configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
2020-03-23T23:51:28.7513823Z configure: writing `config.toml` in current directory
2020-03-23T23:51:28.7514060Z configure: 
2020-03-23T23:51:28.7514517Z configure: run `python /checkout/x.py --help`
2020-03-23T23:51:28.7514742Z configure: 
---
2020-03-23T23:59:35.8031946Z skip untracked path cpu-usage.csv during rustfmt invocations
2020-03-23T23:59:35.8032398Z skip untracked path src/doc/book/ during rustfmt invocations
2020-03-23T23:59:35.8037684Z skip untracked path src/doc/rust-by-example/ during rustfmt invocations
2020-03-23T23:59:35.8041468Z skip untracked path src/llvm-project/ during rustfmt invocations
2020-03-23T23:59:38.7035608Z Diff in /checkout/src/libstd/io/mod.rs at line 952:
2020-03-23T23:59:38.7036617Z  pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>);
2020-03-23T23:59:38.7037035Z  
2020-03-23T23:59:38.7037493Z  #[stable(feature = "iovec-send-sync", since = "1.44.0")]
2020-03-23T23:59:38.7037988Z -unsafe impl<'a> Send for IoSliceMut<'a> { }
2020-03-23T23:59:38.7038459Z +unsafe impl<'a> Send for IoSliceMut<'a> {}
2020-03-23T23:59:38.7038654Z  
2020-03-23T23:59:38.7039066Z  #[stable(feature = "iovec-send-sync", since = "1.44.0")]
2020-03-23T23:59:38.7039557Z -unsafe impl<'a> Sync for IoSliceMut<'a> { }
2020-03-23T23:59:38.7040002Z +unsafe impl<'a> Sync for IoSliceMut<'a> {}
2020-03-23T23:59:38.7040197Z  
2020-03-23T23:59:38.7040417Z  #[stable(feature = "iovec", since = "1.36.0")]
2020-03-23T23:59:38.7040981Z  impl<'a> fmt::Debug for IoSliceMut<'a> {
2020-03-23T23:59:38.7041263Z Diff in /checkout/src/libstd/io/mod.rs at line 1061:
2020-03-23T23:59:38.7041746Z  pub struct IoSlice<'a>(sys::io::IoSlice<'a>);
2020-03-23T23:59:38.7041955Z  
2020-03-23T23:59:38.7042351Z  #[stable(feature = "iovec-send-sync", since = "1.44.0")]
2020-03-23T23:59:38.7042824Z -unsafe impl<'a> Send for IoSlice<'a> { }
2020-03-23T23:59:38.7043247Z +unsafe impl<'a> Send for IoSlice<'a> {}
2020-03-23T23:59:38.7043437Z  
2020-03-23T23:59:38.7043831Z  #[stable(feature = "iovec-send-sync", since = "1.44.0")]
2020-03-23T23:59:38.7044288Z -unsafe impl<'a> Sync for IoSlice<'a> { }
2020-03-23T23:59:38.7044705Z +unsafe impl<'a> Sync for IoSlice<'a> {}
2020-03-23T23:59:38.7044888Z  
2020-03-23T23:59:38.7045098Z  #[stable(feature = "iovec", since = "1.36.0")]
2020-03-23T23:59:38.7045528Z  impl<'a> fmt::Debug for IoSlice<'a> {
2020-03-23T23:59:38.7049410Z Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/src/libstd/io/mod.rs"` failed.
2020-03-23T23:59:38.7050415Z If you're running `tidy`, try again with `--bless` flag. Or, you just want to format code, run `./x.py fmt` instead.
2020-03-23T23:59:38.7075866Z Build completed unsuccessfully in 0:00:41
2020-03-23T23:59:38.7125660Z == clock drift check ==
2020-03-23T23:59:38.7138717Z   local time: Mon Mar 23 23:59:38 UTC 2020
2020-03-23T23:59:39.0031428Z   network time: Mon, 23 Mar 2020 23:59:38 GMT
2020-03-23T23:59:39.0031428Z   network time: Mon, 23 Mar 2020 23:59:38 GMT
2020-03-23T23:59:39.0035185Z == end clock drift check ==
2020-03-23T23:59:40.5267665Z 
2020-03-23T23:59:40.5341988Z ##[error]Bash exited with code '1'.
2020-03-23T23:59:40.5354715Z ##[section]Finishing: Run build
2020-03-23T23:59:40.5400257Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/70342/merge to s
2020-03-23T23:59:40.5404715Z Task         : Get sources
2020-03-23T23:59:40.5405032Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-03-23T23:59:40.5405328Z Version      : 1.0.0
2020-03-23T23:59:40.5405530Z Author       : Microsoft
2020-03-23T23:59:40.5405530Z Author       : Microsoft
2020-03-23T23:59:40.5405838Z Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
2020-03-23T23:59:40.5406224Z ==============================================================================
2020-03-23T23:59:40.8548671Z Cleaning any cached credential from repository: rust-lang/rust (GitHub)
2020-03-23T23:59:40.8604280Z ##[section]Finishing: Checkout rust-lang/rust@refs/pull/70342/merge to s
2020-03-23T23:59:40.8696795Z Cleaning up task key
2020-03-23T23:59:40.8697971Z Start cleaning up orphan processes.
2020-03-23T23:59:40.8888688Z Terminate orphan process: pid (4195) (python)
2020-03-23T23:59:40.9125283Z ##[section]Finishing: Finalize Job

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[Mark-Simulacrum]

Hm, seems like the random target platform would be avoided with an assert that it's Send/Sync. But I agree that in this case it probably won't matter so I'm happy to approve this (with CI passing); r=me

[withoutboats]

@bors r=Mark-Simulacrum

[bors]

📌 Commit 03c64bf has been approved by Mark-Simulacrum