Remove an unneeded doc, fixing the doc build on stable Rust. (#627)

* Remove an unneeded doc, fixing the doc build on stable Rust.

Remove a doc comment which is redundant because it's on a re-export of
an item which already has its own doc comment. This also happens to work
around a bug in at least Rust 1.69.

Fixes #624.

* In the Rust 1.48 CI, pin tempfile to 3.4.0.

tempfile 3.5.0 depends on rustix 0.37. Pin to tempfile 3.4.0 since it
uses rustix 0.36 as this is the rustix 0.36 branch.

* Temporarily disable tests on Windows.

* Disable `test_backends` on Rust 1.48.

* Disable FreeBSD CI for now. (#530) (#600)

FreeBSD CI is currently broken with this error

```
[4/4] Extracting curl-7.88.1: .......... done
curl https://sh.rustup.rs -sSf --output rustup.sh
ld-elf.so.1: /usr/local/lib/libcurl.so.4: Undefined symbol "nghttp2_option_set_no_rfc9113_leading_and_trailing_ws_validation"
```

From some quick searches I found [this bug] which looks related, but I
didn't see anything in the discussion which would let us work around the
problem.

[this bug]: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=269253

Author: sunfishcode

.cirrus.yml

@@ -1,16 +1,22 @@
 # Implementation derived from `.cirrus.yml` in Rust's libc bindings
 # at revision 7f4774e76bd5cb9ccb7140d71ef9be9c16009cdf.
 
-task:
-  name: stable x86_64-unknown-freebsd-13
-  freebsd_instance:
-    image_family: freebsd-13-1
-  setup_script:
-    - pkg install -y curl
-    - curl https://sh.rustup.rs -sSf --output rustup.sh
-    - sh rustup.sh --default-toolchain stable -y --profile=minimal
-    - . $HOME/.cargo/env
-    - rustup default stable
-  test_script:
-    - . $HOME/.cargo/env
-    - cargo test --workspace --features=all-apis
+# Disable FreeBSD testing for now, as we currently hit this error:
+#
+# [4/4] Extracting curl-7.88.1: .......... done
+# curl https://sh.rustup.rs -sSf --output rustup.sh
+# ld-elf.so.1: /usr/local/lib/libcurl.so.4: Undefined symbol "nghttp2_option_set_no_rfc9113_leading_and_trailing_ws_validation"
+
+#task:
+#  name: stable x86_64-unknown-freebsd-13
+#  freebsd_instance:
+#    image_family: freebsd-13-1
+#  setup_script:
+#    - pkg install -y curl
+#    - curl https://sh.rustup.rs -sSf --output rustup.sh
+#    - sh rustup.sh --default-toolchain stable -y --profile=minimal
+#    - . $HOME/.cargo/env
+#    - rustup default stable
+#  test_script:
+#    - . $HOME/.cargo/env
+#    - cargo test --workspace --features=all-apis

.github/workflows/main.yml

@@ -91,6 +91,7 @@ jobs:
       if: matrix.rust == '1.48'
       run: |
         cargo update --package=once_cell --precise 1.14.0
+        cargo update --package=tempfile --precise=3.4.0
         cargo update --package=io-lifetimes --precise 1.0.6
         for crate in test-crates/*; do
             cd $crate
@@ -532,6 +533,7 @@ jobs:
       if: matrix.rust == '1.48'
       run: |
         cargo update --package=once_cell --precise 1.14.0
+        cargo update --package=tempfile --precise=3.4.0
         cargo update --package=io-lifetimes --precise 1.0.6
         for crate in test-crates/*; do
             cd $crate

src/io/read_write.rs

@@ -11,7 +11,6 @@ pub use backend::io::io_slice::{IoSlice, IoSliceMut};
 #[cfg(feature = "std")]
 pub use std::io::{IoSlice, IoSliceMut};
 
-/// `RWF_*` constants for use with [`preadv2`] and [`pwritev2`].
 #[cfg(any(target_os = "android", target_os = "linux"))]
 pub use backend::io::types::ReadWriteFlags;
 

tests/backends.rs

@@ -2,6 +2,13 @@ use std::process::Command;
 
 #[test]
 fn test_backends() {
+    // Test whether `has_dependency` works. `cargo tree` no longer works in
+    // Rust 1.48 because `cargo tree` pulls in dependencies for all targets,
+    // and hermit-core isn't compatible with Rust 1.48.
+    if !has_dependency(".", &[], &[], &[], "io-lifetimes") {
+        return;
+    }
+
     // Pick an arbitrary platform where linux_raw is enabled by default and
     // ensure that the use-default crate uses it.
     #[cfg(all(target_os = "linux", target_arch = "aarch64"))]
@@ -54,6 +61,15 @@ fn test_backends() {
     #[cfg(any(unix, target_os = "wasi"))]
     let libc_dep = "libc";
 
+    // FIXME: Temporarily disable the subsequent tests on Windows until
+    // rust-errno updates to windows-sys 0.48.
+    #[cfg(windows)]
+    {
+        if true {
+            return;
+        }
+    }
+
     // Test the use-libc crate, which enables the "use-libc" cargo feature.
     assert!(
         has_dependency("test-crates/use-libc", &[], &[], &["RUSTFLAGS"], libc_dep),