std: net: Add function to return the system hostname

Author: orowith2os

library/std/src/net/hostname.rs

@@ -0,0 +1,35 @@
+use libc::gethostname;
+use std::ffi::CStr;
+use std::ffi::OsString;
+use std::os::raw::c_char;
+
+/// Returns the system hostname.
+///
+/// The returned result will, on success, return the same result [`libc::gethostname`] would return
+/// (as it is implemented using the very same function), and on error, what `errno` contains, also
+/// set by [`libc::gethostname`].
+#[unstable(feature = "gethostname", issue = "135142")]
+pub fn hostname() -> std::io::Result<OsString> {
+    // 255 bytes is the maximum allowable length for a hostname (as per the DNS spec),
+    // so we shouldn't ever have problems with this. I (@orowith2os) considered using a constant
+    // and letting the platform set the length, but it was determined after some discussion that
+    // this could break things if the platform changes their length. Possible alternative is to
+    // read the sysconf setting for the max hostname length, but that might be a bit too much work.
+    let mut temp_buffer: [c_char; 255] = [0; 255];
+    // 0 = no problem, and there isn't any other relevant error code to check for. Only stuff for
+    // sethostname, and ENAMETOOLONG, which is only relevant for glibc 2.1 or newer. With the
+    // previous information given in mind, we shouldn't ever encounter any error other than the
+    // fact that the system *somehow* failed to get the hostname.
+    // SAFETY: should never be unsafe, as we're passing in a valid (0-initialized) buffer, and the
+    // length of said buffer.
+    let gethostname_result = unsafe { gethostname(&mut temp_buffer as _, temp_buffer.len()) };
+
+    match gethostname_result {
+        0 => {
+            // SAFETY: we already know the pointer here is valid, we made it from safe Rust earlier.
+            let cstring = unsafe { CStr::from_ptr(&mut temp_buffer as _) };
+            return Ok(OsString::from(cstring.to_string_lossy().as_ref()));
+        }
+        _ => Err(std::io::Error::last_os_error()),
+    }
+}

library/std/src/net/mod.rs

@@ -1,7 +1,8 @@
 //! Networking primitives for TCP/UDP communication.
 //!
 //! This module provides networking functionality for the Transmission Control and User
-//! Datagram Protocols, as well as types for IP and socket addresses.
+//! Datagram Protocols, as well as types for IP and socket addresses, and functions related 
+//! to network properties.
 //!
 //! # Organization
 //!
@@ -35,13 +36,16 @@ pub use self::tcp::{Incoming, TcpListener, TcpStream};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::udp::UdpSocket;
 use crate::io::{self, ErrorKind};
+#[unstable(feature = "gethostname", issue = "135142")]
+pub use self::hostname::hostname;
 
 mod ip_addr;
 mod socket_addr;
 mod tcp;
 #[cfg(test)]
 pub(crate) mod test;
 mod udp;
+mod hostname;
 
 /// Possible values which can be passed to the [`TcpStream::shutdown`] method.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]

src/doc/rustc-dev-guide/README.md

@@ -70,46 +70,21 @@ $ ENABLE_LINKCHECK=1 mdbook serve
 We use `mdbook-toc` to auto-generate TOCs for long sections. You can invoke the preprocessor by
 including the `<!-- toc -->` marker at the place where you want the TOC.
 
-## How to fix toolstate failures
-
-> [!NOTE]
-> Currently, we do not track the rustc-dev-guide toolstate due to
-> [spurious failures](https://github.com/rust-lang/rust/pull/71731),
-> but we leave these instructions for when we do it again in the future.
-
-1. You will get a ping from the toolstate commit. e.g. https://github.com/rust-lang-nursery/rust-toolstate/commit/8ffa0e4c30ac9ba8546b7046e5c4ccc2b96ebdd4
-
-2. The commit contains a link to the PR that caused the breakage. e.g. https://github.com/rust-lang/rust/pull/64321
-
-3. If you go to that PR's thread, there is a post from bors with a link to the CI status: https://github.com/rust-lang/rust/pull/64321#issuecomment-529763807
-
-4. Follow the check-actions link to get to the Actions page for that build
-
-5. There will be approximately 1 billion different jobs for the build. They are for different configurations and platforms. The rustc-dev-guide build only runs on the Linux x86_64-gnu-tools job. So click on that job in the list, which is about 60% down in the list.
-
-6. Click the Run build step in the job to get the console log for the step.
-
-7. Click on the log and Ctrl-f to get a search box in the log
-
-8. Search for rustc-dev-guide. This gets you to the place where the links are checked. It is usually ~11K lines into the log.
-
-9. Look at the links in the log near that point in the log
-
-10. Fix those links in the rustc-dev-guide (by making a PR in the rustc-dev-guide repo)
-
-11. Make a PR on the rust-lang/rust repo to update the rustc-dev-guide git submodule in src/docs/rustc-dev-guide.
-To make a PR, the following steps are useful.
-
-```bash
-# Assuming you already cloned the rust-lang/rust repo and you're in the correct directory
-git submodule update --remote src/doc/rustc-dev-guide
-git add -u
-git commit -m "Update rustc-dev-guide"
-# Note that you can use -i, which is short for --incremental, in the following command
-./x test --incremental src/doc/rustc-dev-guide # This is optional and should succeed anyway
-# Open a PR in rust-lang/rust
-```
-
-12. Wait for PR to merge
-
-Voilà!
+## Synchronizing josh subtree with rustc
+
+This repository is linked to `rust-lang/rust` as a [josh](https://josh-project.github.io/josh/intro.html) subtree. You can use the following commands to synchronize the subtree in both directions.
+
+### Pull changes from `rust-lang/rust` into this repository
+1) Checkout a new branch that will be used to create a PR into `rust-lang/rustc-dev-guide`
+2) Run the pull command
+    ```
+    $ cargo run --manifest-path josh-sync/Cargo.toml rustc-pull
+    ```
+3) Push the branch to your fork and create a PR into `rustc-dev-guide`
+
+### Push changes from this repository into `rust-lang/rust`
+1) Run the push command to create a branch named `<branch-name>` in a `rustc` fork under the `<gh-username>` account
+    ```
+    $ cargo run --manifest-path josh-sync/Cargo.toml rustc-push <branch-name> <gh-username>
+    ```
+2) Create a PR from `<branch-name>` into `rust-lang/rust`