Adapt aio to the world of async/await, and fix some potential unsound…

…ness.

* libc::aiocb must not be moved while the kernel has a pointer to it.
  This change enforces that requirement by using std::pin.

* Split LioCbBuilder out of LioCb.  struct LioCb relied on the
  (incorrect) assumption that a Vec's elements have a stable location in
  memory.  That's not true; they can be moved during Vec::push.  The
  solution is to use a Vec in the new Builder struct, but finalize it to
  a boxed slice (which doesn't support push) before allowing it to be
  submitted to the kernel.

* Eliminate owned buffer types.  mio-aio no longer uses owned buffers
  with nix::aio.  There's little need for it in the world of
  async/await.  I'm not aware of any other consumers.  This
  substantially simplifies the code.

.cirrus.yml

@@ -15,7 +15,7 @@ task:
     image: freebsd-11-4-release-amd64
   setup_script:
     - fetch https://sh.rustup.rs -o rustup.sh
-    - sh rustup.sh -y --profile=minimal --default-toolchain 1.40.0
+    - sh rustup.sh -y --profile=minimal --default-toolchain 1.41.0
     - $HOME/.cargo/bin/rustup target add i686-unknown-freebsd
   amd64_test_script:
     - . $HOME/.cargo/env
@@ -46,7 +46,7 @@ task:
     image: catalina-xcode
   setup_script:
     - curl --proto '=https' --tlsv1.2 -sSf -o rustup.sh https://sh.rustup.rs
-    - sh rustup.sh -y --profile=minimal --default-toolchain 1.40.0
+    - sh rustup.sh -y --profile=minimal --default-toolchain 1.41.0
     - . $HOME/.cargo/env
     - bash ci/install.sh
   script:
@@ -101,7 +101,7 @@ task:
   setup_script:
     - mkdir /tmp/home
     - curl --proto '=https' --tlsv1.2 -sSf -o rustup.sh https://sh.rustup.rs
-    - sh rustup.sh -y --profile=minimal --default-toolchain 1.40.0
+    - sh rustup.sh -y --profile=minimal --default-toolchain 1.41.0
     - . $HOME/.cargo/env
     - bash ci/install.sh
   script:
@@ -119,13 +119,13 @@ task:
     - name: Linux x86_64
       env:
         TARGET: x86_64-unknown-linux-gnu
-        TOOLCHAIN: 1.40.0
+        TOOLCHAIN: 1.41.0
     - name: Linux x86_64 musl
       env:
         TARGET: x86_64-unknown-linux-musl
-        TOOLCHAIN: 1.40.0
+        TOOLCHAIN: 1.41.0
   container:
-    image: rust:1.40
+    image: rust:1.41
   setup_script:
     - rustup toolchain install $TOOLCHAIN
     - rustup target add --toolchain $TOOLCHAIN $TARGET
@@ -173,7 +173,7 @@ task:
       env:
         TARGET: x86_64-fuchsia
   container:
-    image: rust:1.40
+    image: rust:1.41
   setup_script:
     - rustup target add $TARGET
   script:

CHANGELOG.md

@@ -16,6 +16,18 @@ This project adheres to [Semantic Versioning](https://semver.org/).
   (#[1429](https://github.com/nix-rust/nix/pull/1429))
 - Made `Uid::is_root` a `const fn`
   (#[1429](https://github.com/nix-rust/nix/pull/1429))
+- `AioCb` is now always pinned.  Once a `libc::aiocb` gets sent to the kernel,
+  its address in memory must not change.  Nix now enforces that by using
+  `std::pin`.  Most users won't need to change anything, except when using
+  `aio_suspend`.  See that method's documentation for the new usage.
+  (#[1440](https://github.com/nix-rust/nix/pull/1440))
+- `LioCb` is now constructed using a distinct `LioCbBuilder` struct.  This
+  avoids a soundness issue with the old `LioCb`.  Usage is similar but
+  construction now uses the builder pattern.  See the documentation for
+  details.
+  (#[1440](https://github.com/nix-rust/nix/pull/1440))
+- Minimum supported Rust version is now 1.41.0.
+  ([#1440](https://github.com/nix-rust/nix/pull/1440))
 
 ### Fixed
 - Allow `sockaddr_ll` size, as reported by the Linux kernel, to be smaller then it's definition
@@ -28,6 +40,11 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - Removed `sys::socket::accept4` from Android arm because libc removed it in
   version 0.2.87.
   ([#1399](https://github.com/nix-rust/nix/pull/1399))
+- `AioCb::from_boxed_slice` and `AioCb::from_boxed_mut_slice` have been
+  removed.  They were useful with earlier versions of Rust, but should no
+  longer be needed now that async/await are available.  `AioCb`s now work
+  exclusively with borrowed buffers, not owned ones.
+  (#[1440](https://github.com/nix-rust/nix/pull/1440))
 
 ## [0.20.0] - 20 February 2021
 ### Added

Cargo.toml

@@ -43,7 +43,7 @@ memoffset = "0.6.3"
 cc = "1"