Auto merge of #146812 - matthiaskrgr:rollup-aiap18m, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - rust-lang/rust#144592 (generate list of all variants with `target_spec_enum`)
 - rust-lang/rust#146762 (Fix and provide instructions for running test suite on Apple simulators)
 - rust-lang/rust#146770 (fixes for numerous clippy warnings)
 - rust-lang/rust#146774 (Allow running `x <cmd> <path>` from a different directory)
 - rust-lang/rust#146800 (Fix unsupported `std::sys::thread` after move)

r? `@ghost`
`@rustbot` modify labels: rollup

7 files changed, 83 insertions, 50 deletions

diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index 75c8ee36528..8226b4325b6 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -590,18 +590,30 @@ impl StepDescription {
         // Attempt to resolve paths to be relative to the builder source directory.
         let mut paths: Vec<PathBuf> = paths
             .iter()
-            .map(|p| {
+            .map(|original_path| {
+                let mut path = original_path.clone();
+
+                // Someone could run `x <cmd> <path>` from a different repository than the source
+                // directory.
+                // In that case, we should not try to resolve the paths relative to the working
+                // directory, but rather relative to the source directory.
+                // So we forcefully "relocate" the path to the source directory here.
+                if !path.is_absolute() {
+                    path = builder.src.join(path);
+                }
+
                 // If the path does not exist, it may represent the name of a Step, such as `tidy` in `x test tidy`
-                if !p.exists() {
-                    return p.clone();
+                if !path.exists() {
+                    // Use the original path here
+                    return original_path.clone();
                 }
 
                 // Make the path absolute, strip the prefix, and convert to a PathBuf.
-                match std::path::absolute(p) {
+                match std::path::absolute(&path) {
                     Ok(p) => p.strip_prefix(&builder.src).unwrap_or(&p).to_path_buf(),
                     Err(e) => {
                         eprintln!("ERROR: {e:?}");
-                        panic!("Due to the above error, failed to resolve path: {p:?}");
+                        panic!("Due to the above error, failed to resolve path: {path:?}");
                     }
                 }
             })
diff --git a/src/doc/rustc-dev-guide/src/tests/running.md b/src/doc/rustc-dev-guide/src/tests/running.md
index 317b65f98cd..482f3c42578 100644
--- a/src/doc/rustc-dev-guide/src/tests/running.md
+++ b/src/doc/rustc-dev-guide/src/tests/running.md
@@ -339,9 +339,34 @@ results.  The Docker image is set up to launch `remote-test-server` and the
 build tools use `remote-test-client` to communicate with the server to
 coordinate running tests (see [src/bootstrap/src/core/build_steps/test.rs]).
 
-> **TODO**
->
-> - Is there any support for using an iOS emulator?
+To run on the iOS/tvOS/watchOS/visionOS simulator, we can similarly treat it as
+a "remote" machine. A curious detail here is that the network is shared between
+the simulator instance and the host macOS, so we can use the local loopback
+address `127.0.0.1`. Something like the following should work:
+
+```sh
+# Build the test server for the iOS simulator:
+./x build src/tools/remote-test-server --target aarch64-apple-ios-sim
+
+# If you already have a simulator instance open, copy the device UUID from:
+xcrun simctl list devices booted
+UDID=01234567-89AB-CDEF-0123-456789ABCDEF
+
+# Alternatively, create and boot a new simulator instance:
+xcrun simctl list runtimes
+xcrun simctl list devicetypes
+UDID=$(xcrun simctl create $CHOSEN_DEVICE_TYPE $CHOSEN_RUNTIME)
+xcrun simctl boot $UDID
+# See https://nshipster.com/simctl/ for details.
+
+# Spawn the runner on port 12345:
+xcrun simctl spawn $UDID ./build/host/stage2-tools/aarch64-apple-ios-sim/release/remote-test-server -v --bind 127.0.0.1:12345
+
+# In a new terminal, run tests via the runner:
+export TEST_DEVICE_ADDR="127.0.0.1:12345"
+./x test --host='' --target aarch64-apple-ios-sim --skip tests/debuginfo
+# FIXME(madsmtm): Allow debuginfo tests to work (maybe needs `.dSYM` folder to be copied to the target?).
+```
 
 [armhf-gnu]: https://github.com/rust-lang/rust/tree/master/src/ci/docker/host-x86_64/armhf-gnu/Dockerfile
 [QEMU]: https://www.qemu.org/
diff --git a/src/doc/rustc/src/platform-support/apple-ios.md b/src/doc/rustc/src/platform-support/apple-ios.md
index 586afa65226..3ac14704754 100644
--- a/src/doc/rustc/src/platform-support/apple-ios.md
+++ b/src/doc/rustc/src/platform-support/apple-ios.md
@@ -66,6 +66,11 @@ Rust programs can be built for these targets by specifying `--target`, if
 $ rustc --target aarch64-apple-ios your-code.rs
 ```
 
+Or if using Cargo and `-Zbuild-std`:
+```console
+$ cargo +nightly build -Zbuild-std --target armv7s-apple-ios
+```
+
 The simulator variants can be differentiated from the variants running
 on-device with the `target_env = "sim"` cfg (or `target_abi = "sim"` before
 Rust CURRENT_RUSTC_VERSION).
@@ -73,7 +78,7 @@ Rust CURRENT_RUSTC_VERSION).
 ```rust
 if cfg!(all(target_vendor = "apple", target_env = "sim")) {
     // Do something on the iOS/tvOS/visionOS/watchOS Simulator.
-} {
+} else {
     // Everything else, like Windows and non-Simulator iOS.
 }
 ```
@@ -82,8 +87,15 @@ This is similar to the `TARGET_OS_SIMULATOR` define in C code.
 
 ## Testing
 
-There is no support for running the Rust or standard library testsuite at the
-moment. Testing has mostly been done manually with builds of static libraries
-embedded into applications called from Xcode or a simulator.
+Running and testing your code naturally requires either an actual device
+running iOS, or the equivalent Xcode simulator environment. There exists
+several tools in the ecosystem for running a Cargo project on one of these.
+One of these tools is [`cargo-dinghy`]. [madsmtm/objc2#459] contains a more
+exhaustive list.
+
+See also [testing on emulators in the `rustc-dev-guide`][test-sim] for
+instructions on running the standard library's test suite.
 
-It hopefully will be possible to improve this in the future.
+[`cargo-dinghy`]: https://github.com/sonos/dinghy
+[madsmtm/objc2#459]: https://github.com/madsmtm/objc2/issues/459
+[test-sim]: https://rustc-dev-guide.rust-lang.org/tests/running.html#testing-on-emulators
diff --git a/src/doc/rustc/src/platform-support/apple-tvos.md b/src/doc/rustc/src/platform-support/apple-tvos.md
index 193d6466612..a952d8e230d 100644
--- a/src/doc/rustc/src/platform-support/apple-tvos.md
+++ b/src/doc/rustc/src/platform-support/apple-tvos.md
@@ -65,17 +65,8 @@ Using the unstable `-Zbuild-std` with a nightly Cargo may also work.
 
 ## Building Rust programs
 
-Rust programs can be built for these targets by specifying `--target`, if
-`rustc` has been built with support for them. For example:
-
-```console
-$ rustc --target aarch64-apple-tvos your-code.rs
-```
+See [the instructions for iOS](./apple-ios.md#building-rust-programs).
 
 ## Testing
 
-There is no support for running the Rust or standard library testsuite at the
-moment. Testing has mostly been done manually with builds of static libraries
-embedded into applications called from Xcode or a simulator.
-
-It hopefully will be possible to improve this in the future.
+See [the instructions for iOS](./apple-ios.md#testing).
diff --git a/src/doc/rustc/src/platform-support/apple-visionos.md b/src/doc/rustc/src/platform-support/apple-visionos.md
index ed96912da7a..2ac069248ee 100644
--- a/src/doc/rustc/src/platform-support/apple-visionos.md
+++ b/src/doc/rustc/src/platform-support/apple-visionos.md
@@ -46,20 +46,11 @@ be fixed in [#124560](https://github.com/rust-lang/rust/pull/124560).
 
 ## Building Rust programs
 
-Rust programs can be built for these targets by specifying `--target`, if
-`rustc` has been built with support for them. For example:
-
-```console
-$ rustc --target aarch64-apple-visionos-sim your-code.rs
-```
+See [the instructions for iOS](./apple-ios.md#building-rust-programs).
 
 ## Testing
 
-There is no support for running the Rust or standard library testsuite at the
-moment. Testing has mostly been done manually with builds of static libraries
-embedded into applications called from Xcode or a simulator.
-
-It hopefully will be possible to improve this in the future.
+See [the instructions for iOS](./apple-ios.md#testing).
 
 ## Cross-compilation toolchains and C code
 
diff --git a/src/doc/rustc/src/platform-support/apple-watchos.md b/src/doc/rustc/src/platform-support/apple-watchos.md
index 6ac09d0d1e5..c1a00961425 100644
--- a/src/doc/rustc/src/platform-support/apple-watchos.md
+++ b/src/doc/rustc/src/platform-support/apple-watchos.md
@@ -50,17 +50,8 @@ Using the unstable `-Zbuild-std` with a nightly Cargo may also work.
 
 ## Building Rust programs
 
-Rust programs can be built for these targets by specifying `--target`, if
-`rustc` has been built with support for them. For example:
-
-```console
-$ rustc --target aarch64-apple-watchos-sim your-code.rs
-```
+See [the instructions for iOS](./apple-ios.md#building-rust-programs).
 
 ## Testing
 
-There is no support for running the Rust or standard library testsuite at the
-moment. Testing has mostly been done manually with builds of static libraries
-embedded into applications called from Xcode or a simulator.
-
-It hopefully will be possible to improve this in the future.
+See [the instructions for iOS](./apple-ios.md#testing).
diff --git a/src/tools/remote-test-server/src/main.rs b/src/tools/remote-test-server/src/main.rs
index 67a7ad6f3b4..5ec5e6e2898 100644
--- a/src/tools/remote-test-server/src/main.rs
+++ b/src/tools/remote-test-server/src/main.rs
@@ -53,6 +53,10 @@ impl Config {
             batch: false,
             bind: if cfg!(target_os = "android") || cfg!(windows) {
                 ([0, 0, 0, 0], 12345).into()
+            } else if cfg!(target_env = "sim") {
+                // iOS/tvOS/watchOS/visionOS simulators share network device
+                // with the host machine.
+                ([127, 0, 0, 1], 12345).into()
             } else {
                 ([10, 0, 2, 15], 12345).into()
             },
@@ -262,10 +266,17 @@ fn handle_run(socket: TcpStream, work: &Path, tmp: &Path, lock: &Mutex<()>, conf
     cmd.args(args);
     cmd.envs(env);
 
-    // On windows, libraries are just searched in the executable directory,
-    // system directories, PWD, and PATH, in that order. PATH is the only one
-    // we can change for this.
-    let library_path = if cfg!(windows) { "PATH" } else { "LD_LIBRARY_PATH" };
+    let library_path = if cfg!(windows) {
+        // On windows, libraries are just searched in the executable directory,
+        // system directories, PWD, and PATH, in that order. PATH is the only
+        // one we can change for this.
+        "PATH"
+    } else if cfg!(target_vendor = "apple") {
+        // On Apple platforms, the environment variable is named differently.
+        "DYLD_LIBRARY_PATH"
+    } else {
+        "LD_LIBRARY_PATH"
+    };
 
     // Support libraries were uploaded to `work` earlier, so make sure that's
     // in `LD_LIBRARY_PATH`. Also include our own current dir which may have