Rollup merge of #146762 - madsmtm:test-apple-sim, r=jieyouxu

Fix and provide instructions for running test suite on Apple simulators

The following now works:

```sh
./x test --host='' --target aarch64-apple-ios-sim --skip tests/debuginfo
./x test --host='' --target aarch64-apple-tvos-sim --skip tests/debuginfo
./x test --host='' --target aarch64-apple-watchos-sim --skip tests/debuginfo
./x test --host='' --target aarch64-apple-visionos-sim --skip tests/debuginfo
```

I have documented the setup I used [in the `rustc-dev-guide`](https://rustc-dev-guide.rust-lang.org/tests/running.html#testing-on-emulators), it's fairly standard use of `remote-test-server` (with a small fix to library load paths which I've made in the first commit).

I first tried the somewhat simpler `target.aarch64-apple-ios-sim.runner = "xcrun simctl spawn $UDID"`, but that doesn't work as required libraries etc. also need to be copied to the device.

The debuginfo tests fail, I think because the debug info in `.dSYM` isn't available. I am yet unsure exactly how to fix this, either we need to copy that directory to the target as well, or we need to configure `lldb` somehow to read it from the host.

I decided to not add this to our CI, since I suspect we wouldn't gain much from it? Running on the simulator still uses the host Darwin kernel, it's basically just configured to run in another mode with more restricted permissions and different system libraries.

r? jieyouxu
CC ``@simlay,`` you're a lot more familiar with `xcrun simctl` than I.

33 files changed, 245 insertions, 77 deletions

diff --git a/library/std/src/os/unix/process.rs b/library/std/src/os/unix/process.rs
index 09429af06e3..5b7b5a8ea80 100644
--- a/library/std/src/os/unix/process.rs
+++ b/library/std/src/os/unix/process.rs
@@ -406,8 +406,10 @@ pub trait ChildExt: Sealed {
     /// use libc::SIGTERM;
     ///
     /// fn main() -> io::Result<()> {
+    ///     # if cfg!(not(all(target_vendor = "apple", not(target_os = "macos")))) {
     ///     let child = Command::new("cat").stdin(Stdio::piped()).spawn()?;
     ///     child.send_signal(SIGTERM)?;
+    ///     # }
     ///     Ok(())
     /// }
     /// ```
diff --git a/library/std/src/process.rs b/library/std/src/process.rs
index 48265de90c4..0883e56342c 100644
--- a/library/std/src/process.rs
+++ b/library/std/src/process.rs
@@ -532,6 +532,7 @@ impl fmt::Debug for ChildStderr {
 /// to be changed (for example, by adding arguments) prior to spawning:
 ///
 /// ```
+/// # if cfg!(not(all(target_vendor = "apple", not(target_os = "macos")))) {
 /// use std::process::Command;
 ///
 /// let output = if cfg!(target_os = "windows") {
@@ -548,6 +549,7 @@ impl fmt::Debug for ChildStderr {
 /// };
 ///
 /// let hello = output.stdout;
+/// # }
 /// ```
 ///
 /// `Command` can be reused to spawn multiple processes. The builder methods
@@ -1348,7 +1350,7 @@ impl Output {
     ///
     /// ```
     /// #![feature(exit_status_error)]
-    /// # #[cfg(all(unix, not(target_os = "android")))] {
+    /// # #[cfg(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos")))))] {
     /// use std::process::Command;
     /// assert!(Command::new("false").output().unwrap().exit_ok().is_err());
     /// # }
@@ -1695,7 +1697,7 @@ impl From<io::Stdout> for Stdio {
     /// # Ok(())
     /// # }
     /// #
-    /// # if cfg!(all(unix, not(target_os = "android"))) {
+    /// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// #     test().unwrap();
     /// # }
     /// ```
@@ -1724,7 +1726,7 @@ impl From<io::Stderr> for Stdio {
     /// # Ok(())
     /// # }
     /// #
-    /// # if cfg!(all(unix, not(target_os = "android"))) {
+    /// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// #     test().unwrap();
     /// # }
     /// ```
@@ -1800,7 +1802,7 @@ impl ExitStatus {
     ///
     /// ```
     /// #![feature(exit_status_error)]
-    /// # if cfg!(unix) {
+    /// # if cfg!(all(unix, not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// use std::process::Command;
     ///
     /// let status = Command::new("ls")
@@ -1907,7 +1909,7 @@ impl crate::sealed::Sealed for ExitStatusError {}
 ///
 /// ```
 /// #![feature(exit_status_error)]
-/// # if cfg!(all(unix, not(target_os = "android"))) {
+/// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
 /// use std::process::{Command, ExitStatusError};
 ///
 /// fn run(cmd: &str) -> Result<(), ExitStatusError> {
@@ -1950,7 +1952,7 @@ impl ExitStatusError {
     ///
     /// ```
     /// #![feature(exit_status_error)]
-    /// # #[cfg(all(unix, not(target_os = "android")))] {
+    /// # #[cfg(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos")))))] {
     /// use std::process::Command;
     ///
     /// let bad = Command::new("false").status().unwrap().exit_ok().unwrap_err();
@@ -1975,7 +1977,7 @@ impl ExitStatusError {
     /// ```
     /// #![feature(exit_status_error)]
     ///
-    /// # if cfg!(all(unix, not(target_os = "android"))) {
+    /// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// use std::num::NonZero;
     /// use std::process::Command;
     ///
diff --git a/library/std/src/process/tests.rs b/library/std/src/process/tests.rs
index 5879914ca20..12c5130defe 100644
--- a/library/std/src/process/tests.rs
+++ b/library/std/src/process/tests.rs
@@ -5,7 +5,15 @@ use crate::mem::MaybeUninit;
 use crate::str;
 
 fn known_command() -> Command {
-    if cfg!(windows) { Command::new("help") } else { Command::new("echo") }
+    if cfg!(windows) {
+        Command::new("help")
+    } else if cfg!(all(target_vendor = "apple", not(target_os = "macos"))) {
+        // iOS/tvOS/watchOS/visionOS have a very limited set of commandline
+        // binaries available.
+        Command::new("log")
+    } else {
+        Command::new("echo")
+    }
 }
 
 #[cfg(target_os = "android")]
@@ -19,7 +27,10 @@ fn shell_cmd() -> Command {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn smoke() {
     let p = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 0"]).spawn()
@@ -41,7 +52,10 @@ fn smoke_failure() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn exit_reported_right() {
     let p = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).spawn()
@@ -56,7 +70,10 @@ fn exit_reported_right() {
 
 #[test]
 #[cfg(unix)]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn signal_reported_right() {
     use crate::os::unix::process::ExitStatusExt;
 
@@ -80,7 +97,10 @@ pub fn run_output(mut cmd: Command) -> String {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn stdout_works() {
     if cfg!(target_os = "windows") {
         let mut cmd = Command::new("cmd");
@@ -94,7 +114,11 @@ fn stdout_works() {
 }
 
 #[test]
-#[cfg_attr(any(windows, target_os = "vxworks"), ignore)]
+#[cfg_attr(windows, ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn set_current_dir_works() {
     // On many Unix platforms this will use the posix_spawn path.
     let mut cmd = shell_cmd();
@@ -116,7 +140,11 @@ fn set_current_dir_works() {
 }
 
 #[test]
-#[cfg_attr(any(windows, target_os = "vxworks"), ignore)]
+#[cfg_attr(windows, ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn stdin_works() {
     let mut p = shell_cmd()
         .arg("-c")
@@ -134,7 +162,10 @@ fn stdin_works() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn child_stdout_read_buf() {
     let mut cmd = if cfg!(target_os = "windows") {
         let mut cmd = Command::new("cmd");
@@ -165,7 +196,10 @@ fn child_stdout_read_buf() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_process_status() {
     let mut status = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).status().unwrap()
@@ -191,7 +225,10 @@ fn test_process_output_fail_to_start() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_process_output_output() {
     let Output { status, stdout, stderr } = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "echo hello"]).output().unwrap()
@@ -206,7 +243,10 @@ fn test_process_output_output() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_process_output_error() {
     let Output { status, stdout, stderr } = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "mkdir ."]).output().unwrap()
@@ -221,7 +261,10 @@ fn test_process_output_error() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_finish_once() {
     let mut prog = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).spawn().unwrap()
@@ -232,7 +275,10 @@ fn test_finish_once() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_finish_twice() {
     let mut prog = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).spawn().unwrap()
@@ -244,7 +290,10 @@ fn test_finish_twice() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_wait_with_output_once() {
     let prog = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "echo hello"]).stdout(Stdio::piped()).spawn().unwrap()
@@ -279,7 +328,10 @@ pub fn env_cmd() -> Command {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_override_env() {
     use crate::env;
 
@@ -302,7 +354,10 @@ fn test_override_env() {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_add_to_env() {
     let result = env_cmd().env("RUN_TEST_NEW_ENV", "123").output().unwrap();
     let output = String::from_utf8_lossy(&result.stdout).to_string();
@@ -314,7 +369,10 @@ fn test_add_to_env() {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_capture_env_at_spawn() {
     use crate::env;
 
@@ -378,7 +436,10 @@ fn test_interior_nul_in_current_dir_is_error() {
 
 // Regression tests for #30862.
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no `env` cmd available"
+)]
 fn test_interior_nul_in_env_key_is_error() {
     match env_cmd().env("has-some-\0\0s-inside", "value").spawn() {
         Err(e) => assert_eq!(e.kind(), ErrorKind::InvalidInput),
@@ -387,7 +448,10 @@ fn test_interior_nul_in_env_key_is_error() {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no `env` cmd available"
+)]
 fn test_interior_nul_in_env_value_is_error() {
     match env_cmd().env("key", "has-some-\0\0s-inside").spawn() {
         Err(e) => assert_eq!(e.kind(), ErrorKind::InvalidInput),
diff --git a/library/std/src/sys/process/unix/unix/tests.rs b/library/std/src/sys/process/unix/unix/tests.rs
index f4d6ac6b4e3..663ba61f966 100644
--- a/library/std/src/sys/process/unix/unix/tests.rs
+++ b/library/std/src/sys/process/unix/unix/tests.rs
@@ -51,6 +51,7 @@ fn exitstatus_display_tests() {
 
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)]
+#[cfg_attr(any(target_os = "tvos", target_os = "watchos"), ignore = "fork is prohibited")]
 fn test_command_fork_no_unwind() {
     let got = catch_unwind(|| {
         let mut c = Command::new("echo");
diff --git a/library/std/tests/process_spawning.rs b/library/std/tests/process_spawning.rs
index 43b45cb2d2b..93f73ccad3e 100644
--- a/library/std/tests/process_spawning.rs
+++ b/library/std/tests/process_spawning.rs
@@ -7,6 +7,7 @@ mod common;
 #[test]
 // Process spawning not supported by Miri, Emscripten and wasi
 #[cfg_attr(any(miri, target_os = "emscripten", target_os = "wasi"), ignore)]
+#[cfg_attr(any(target_os = "tvos", target_os = "watchos"), ignore = "fork is prohibited")]
 fn issue_15149() {
     // If we're the parent, copy our own binary to a new directory.
     let my_path = env::current_exe().unwrap();
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
diff --git a/tests/ui/backtrace/apple-no-dsymutil.rs b/tests/ui/backtrace/apple-no-dsymutil.rs
index e5aeced25ca..00c8349d129 100644
--- a/tests/ui/backtrace/apple-no-dsymutil.rs
+++ b/tests/ui/backtrace/apple-no-dsymutil.rs
@@ -3,6 +3,7 @@
 //@ compile-flags:-Cstrip=none
 //@ compile-flags:-g -Csplit-debuginfo=unpacked
 //@ only-apple
+//@ ignore-remote needs the compiler-produced `.o` file to be copied to the device
 
 use std::process::Command;
 use std::str;
diff --git a/tests/ui/backtrace/dylib-dep.rs b/tests/ui/backtrace/dylib-dep.rs
index 05fdb9afef8..cf420ec8d06 100644
--- a/tests/ui/backtrace/dylib-dep.rs
+++ b/tests/ui/backtrace/dylib-dep.rs
@@ -7,6 +7,10 @@
 //@ ignore-android FIXME #17520
 //@ ignore-fuchsia Backtraces not symbolized
 //@ ignore-musl musl doesn't support dynamic libraries (at least when the original test was written).
+//@ ignore-ios needs the `.dSYM` files to be moved to the device
+//@ ignore-tvos needs the `.dSYM` files to be moved to the device
+//@ ignore-watchos needs the `.dSYM` files to be moved to the device
+//@ ignore-visionos needs the `.dSYM` files to be moved to the device
 //@ needs-unwind
 //@ ignore-backends: gcc
 //@ compile-flags: -g -Copt-level=0 -Cstrip=none -Cforce-frame-pointers=yes
diff --git a/tests/ui/backtrace/line-tables-only.rs b/tests/ui/backtrace/line-tables-only.rs
index 6624c71e184..5863cc1d17d 100644
--- a/tests/ui/backtrace/line-tables-only.rs
+++ b/tests/ui/backtrace/line-tables-only.rs
@@ -11,6 +11,10 @@
 //@ ignore-android FIXME #17520
 //@ ignore-fuchsia Backtraces not symbolized
 //@ ignore-emscripten Requires custom symbolization code
+//@ ignore-ios needs the `.dSYM` files to be moved to the device
+//@ ignore-tvos needs the `.dSYM` files to be moved to the device
+//@ ignore-watchos needs the `.dSYM` files to be moved to the device
+//@ ignore-visionos needs the `.dSYM` files to be moved to the device
 //@ needs-unwind
 //@ aux-build: line-tables-only-helper.rs
 
diff --git a/tests/ui/command/command-current-dir.rs b/tests/ui/command/command-current-dir.rs
index e264cbe4d70..a6b51df5f17 100644
--- a/tests/ui/command/command-current-dir.rs
+++ b/tests/ui/command/command-current-dir.rs
@@ -2,6 +2,8 @@
 //@ no-prefer-dynamic We move the binary around, so do not depend dynamically on libstd
 //@ needs-subprocess
 //@ ignore-fuchsia Needs directory creation privilege
+//@ ignore-tvos `Command::current_dir` requires fork, which is prohibited
+//@ ignore-watchos `Command::current_dir` requires fork, which is prohibited
 
 use std::env;
 use std::fs;
diff --git a/tests/ui/command/command-exec.rs b/tests/ui/command/command-exec.rs
index 77336377e88..870f8b047b9 100644
--- a/tests/ui/command/command-exec.rs
+++ b/tests/ui/command/command-exec.rs
@@ -3,6 +3,8 @@
 //@ only-unix (this is a unix-specific test)
 //@ needs-subprocess
 //@ ignore-fuchsia no execvp syscall provided
+//@ ignore-tvos execvp is prohibited
+//@ ignore-watchos execvp is prohibited
 
 use std::env;
 use std::os::unix::process::CommandExt;
diff --git a/tests/ui/command/command-pre-exec.rs b/tests/ui/command/command-pre-exec.rs
index 7299f357bd0..a62ab0b5ed6 100644
--- a/tests/ui/command/command-pre-exec.rs
+++ b/tests/ui/command/command-pre-exec.rs
@@ -2,6 +2,8 @@
 //@ only-unix (this is a unix-specific test)
 //@ needs-subprocess
 //@ ignore-fuchsia no execvp syscall
+//@ ignore-tvos execvp is prohibited
+//@ ignore-watchos execvp is prohibited
 
 #![feature(rustc_private)]
 
diff --git a/tests/ui/command/command-uid-gid.rs b/tests/ui/command/command-uid-gid.rs
index f54a0f50708..ef0653eb2cb 100644
--- a/tests/ui/command/command-uid-gid.rs
+++ b/tests/ui/command/command-uid-gid.rs
@@ -1,6 +1,8 @@
 //@ run-pass
 //@ ignore-android
 //@ ignore-fuchsia no '/bin/sh', '/bin/ls'
+//@ ignore-tvos `Command::uid/gid` requires fork, which is prohibited
+//@ ignore-watchos `Command::uid/gid` requires fork, which is prohibited
 //@ needs-subprocess
 
 #![feature(rustc_private)]
diff --git a/tests/ui/compiletest-self-test/test-aux-bin.rs b/tests/ui/compiletest-self-test/test-aux-bin.rs
index c1c28e12b3b..9ac17e6e146 100644
--- a/tests/ui/compiletest-self-test/test-aux-bin.rs
+++ b/tests/ui/compiletest-self-test/test-aux-bin.rs
@@ -1,4 +1,5 @@
 //@ ignore-cross-compile because aux-bin does not yet support it
+//@ ignore-remote because aux-bin does not yet support it
 //@ aux-bin: print-it-works.rs
 //@ run-pass
 
diff --git a/tests/ui/cross-crate/exporting-impl-from-root-causes-ice-2472.rs b/tests/ui/cross-crate/exporting-impl-from-root-causes-ice-2472.rs
index 86d637b579d..c6cfae1e545 100644
--- a/tests/ui/cross-crate/exporting-impl-from-root-causes-ice-2472.rs
+++ b/tests/ui/cross-crate/exporting-impl-from-root-causes-ice-2472.rs
@@ -1,6 +1,9 @@
 //@ run-pass
 //@ aux-build:exporting-impl-from-root-causes-ice-2472-b.rs
-
+//@ ignore-ios FIXME(madsmtm): For some reason the necessary dylib isn't copied to the remote?
+//@ ignore-tvos FIXME(madsmtm): For some reason the necessary dylib isn't copied to the remote?
+//@ ignore-watchos FIXME(madsmtm): For some reason the necessary dylib isn't copied to the remote?
+//@ ignore-visionos FIXME(madsmtm): For some reason the necessary dylib isn't copied to the remote?
 
 extern crate exporting_impl_from_root_causes_ice_2472_b as lib;
 
diff --git a/tests/ui/issues/issue-45731.rs b/tests/ui/issues/issue-45731.rs
index 49335362dd0..db11d1dbef1 100644
--- a/tests/ui/issues/issue-45731.rs
+++ b/tests/ui/issues/issue-45731.rs
@@ -1,6 +1,10 @@
 //@ run-pass
 #![allow(unused_variables)]
 //@ compile-flags:--test -g
+//@ ignore-ios needs the `.dSYM` files to be moved to the device
+//@ ignore-tvos needs the `.dSYM` files to be moved to the device
+//@ ignore-watchos needs the `.dSYM` files to be moved to the device
+//@ ignore-visionos needs the `.dSYM` files to be moved to the device
 
 #[cfg(target_vendor = "apple")]
 #[test]
diff --git a/tests/ui/process/core-run-destroy.rs b/tests/ui/process/core-run-destroy.rs
index f4be54da8fe..f381997ef79 100644
--- a/tests/ui/process/core-run-destroy.rs
+++ b/tests/ui/process/core-run-destroy.rs
@@ -8,6 +8,10 @@
 //@ needs-subprocess
 //@ ignore-vxworks no 'cat' and 'sleep'
 //@ ignore-fuchsia no 'cat'
+//@ ignore-ios no 'cat' and 'sleep'
+//@ ignore-tvos no 'cat' and 'sleep'
+//@ ignore-watchos no 'cat' and 'sleep'
+//@ ignore-visionos no 'cat' and 'sleep'
 
 // N.B., these tests kill child processes. Valgrind sees these children as leaking
 // memory, which makes for some *confusing* logs. That's why these are here
diff --git a/tests/ui/process/env-funky-keys.rs b/tests/ui/process/env-funky-keys.rs
index a4a71c94020..193659bea29 100644
--- a/tests/ui/process/env-funky-keys.rs
+++ b/tests/ui/process/env-funky-keys.rs
@@ -1,8 +1,7 @@
 //@ run-pass
 //@ edition: 2021
-// Ignore this test on Android, because it segfaults there.
 
-//@ ignore-android
+//@ ignore-android segfaults
 //@ ignore-windows
 //@ ignore-wasm32 no execve
 //@ ignore-sgx no execve
@@ -24,6 +23,9 @@ use std::ptr;
 fn main() {
     if env::args_os().count() == 2 {
         for (key, value) in env::vars_os() {
+            if key == "DYLD_ROOT_PATH" {
+                continue;
+            }
             panic!("found env value {:?} {:?}", key, value);
         }
         return;
@@ -35,7 +37,18 @@ fn main() {
                                        .as_bytes()).unwrap();
     let filename: *const c_char = current_exe.as_ptr();
     let argv: &[*const c_char] = &[filename, filename, ptr::null()];
-    let envp: &[*const c_char] = &[c"FOOBAR".as_ptr(), ptr::null()];
+
+    let root;
+    let envp: &[*const c_char] = if cfg!(all(target_vendor = "apple", target_env = "sim")) {
+        // Workaround: iOS/tvOS/watchOS/visionOS simulators need the root path
+        // from the current process.
+        root = format!("DYLD_ROOT_PATH={}\0", std::env::var("DYLD_ROOT_PATH").unwrap());
+        &[c"FOOBAR".as_ptr(), root.as_ptr().cast(), ptr::null()]
+    } else {
+        // Try to set an environment variable without a value.
+        &[c"FOOBAR".as_ptr(), ptr::null()]
+    };
+
     unsafe {
         execve(filename, &argv[0], &envp[0]);
     }
diff --git a/tests/ui/process/fds-are-cloexec.rs b/tests/ui/process/fds-are-cloexec.rs
index f6678379dd6..0fae7c2b502 100644
--- a/tests/ui/process/fds-are-cloexec.rs
+++ b/tests/ui/process/fds-are-cloexec.rs
@@ -74,8 +74,15 @@ fn child(args: &[String]) {
         let fd: libc::c_int = arg.parse().unwrap();
         unsafe {
             assert_eq!(libc::read(fd, b.as_mut_ptr() as *mut _, 2), -1);
-            assert_eq!(io::Error::last_os_error().raw_os_error(),
-                       Some(libc::EBADF));
+            let raw = io::Error::last_os_error().raw_os_error();
+            if cfg!(all(target_vendor = "apple", not(target_os = "macos"))) {
+                // Workaround: iOS/tvOS/watchOS/visionOS seems to treat `tcp6`
+                // as a directory?
+                if raw == Some(libc::EISDIR) {
+                    continue;
+                }
+            }
+            assert_eq!(raw, Some(libc::EBADF));
         }
     }
 }
diff --git a/tests/ui/process/println-with-broken-pipe.rs b/tests/ui/process/println-with-broken-pipe.rs
index 58b83a2dd9a..e87e2077370 100644
--- a/tests/ui/process/println-with-broken-pipe.rs
+++ b/tests/ui/process/println-with-broken-pipe.rs
@@ -5,6 +5,10 @@
 //@ ignore-fuchsia
 //@ ignore-horizon
 //@ ignore-android
+//@ ignore-ios no 'head'
+//@ ignore-tvos no 'head'
+//@ ignore-watchos no 'head'
+//@ ignore-visionos no 'head'
 //@ ignore-backends: gcc
 //@ normalize-stderr: ".rs:\d+:\d+" -> ".rs:LL:CC"
 //@ compile-flags: -Zon-broken-pipe=error
diff --git a/tests/ui/process/process-envs.rs b/tests/ui/process/process-envs.rs
index 98052f1d3a5..cbe16704a8e 100644
--- a/tests/ui/process/process-envs.rs
+++ b/tests/ui/process/process-envs.rs
@@ -2,6 +2,10 @@
 //@ needs-subprocess
 //@ ignore-vxworks no 'env'
 //@ ignore-fuchsia no 'env'
+//@ ignore-ios no 'env'
+//@ ignore-tvos no 'env'
+//@ ignore-watchos no 'env'
+//@ ignore-visionos no 'env'
 
 use std::process::Command;
 use std::env;
diff --git a/tests/ui/process/process-panic-after-fork.rs b/tests/ui/process/process-panic-after-fork.rs
index 6e0267e0a54..653ff6ce314 100644
--- a/tests/ui/process/process-panic-after-fork.rs
+++ b/tests/ui/process/process-panic-after-fork.rs
@@ -3,6 +3,8 @@
 //@ only-unix
 //@ needs-subprocess
 //@ ignore-fuchsia no fork
+//@ ignore-tvos fork is prohibited
+//@ ignore-watchos fork is prohibited
 
 #![feature(rustc_private)]
 #![feature(never_type)]
diff --git a/tests/ui/process/process-remove-from-env.rs b/tests/ui/process/process-remove-from-env.rs
index c1a2b2daf5b..68c3909b15a 100644
--- a/tests/ui/process/process-remove-from-env.rs
+++ b/tests/ui/process/process-remove-from-env.rs
@@ -2,6 +2,10 @@
 //@ needs-subprocess
 //@ ignore-vxworks no 'env'
 //@ ignore-fuchsia no 'env'
+//@ ignore-ios no 'env'
+//@ ignore-tvos no 'env'
+//@ ignore-watchos no 'env'
+//@ ignore-visionos no 'env'
 
 use std::process::Command;
 use std::env;
diff --git a/tests/ui/process/process-sigpipe.rs b/tests/ui/process/process-sigpipe.rs
index 3ecf271599d..574d79ee1dd 100644
--- a/tests/ui/process/process-sigpipe.rs
+++ b/tests/ui/process/process-sigpipe.rs
@@ -15,6 +15,10 @@
 
 //@ ignore-vxworks no 'sh'
 //@ ignore-fuchsia no 'sh'
+//@ ignore-ios no 'sh'
+//@ ignore-tvos no 'sh'
+//@ ignore-watchos no 'sh'
+//@ ignore-visionos no 'sh'
 //@ needs-threads
 //@ only-unix SIGPIPE is a unix feature
 
diff --git a/tests/ui/process/process-spawn-failure.rs b/tests/ui/process/process-spawn-failure.rs
index 0950b044c97..ac2c34bc783 100644
--- a/tests/ui/process/process-spawn-failure.rs
+++ b/tests/ui/process/process-spawn-failure.rs
@@ -9,6 +9,10 @@
 //@ ignore-vxworks no 'ps'
 //@ ignore-fuchsia no 'ps'
 //@ ignore-nto no 'ps'
+//@ ignore-ios no 'ps'
+//@ ignore-tvos no 'ps'
+//@ ignore-watchos no 'ps'
+//@ ignore-visionos no 'ps'
 
 #![feature(rustc_private)]
 
diff --git a/tests/ui/runtime/backtrace-debuginfo.rs b/tests/ui/runtime/backtrace-debuginfo.rs
index 5fb9943d6c3..5e91f22aec0 100644
--- a/tests/ui/runtime/backtrace-debuginfo.rs
+++ b/tests/ui/runtime/backtrace-debuginfo.rs
@@ -11,6 +11,10 @@
 //@ compile-flags:-Cstrip=none
 //@ needs-subprocess
 //@ ignore-fuchsia Backtrace not symbolized, trace different line alignment
+//@ ignore-ios needs the `.dSYM` files to be moved to the device
+//@ ignore-tvos needs the `.dSYM` files to be moved to the device
+//@ ignore-watchos needs the `.dSYM` files to be moved to the device
+//@ ignore-visionos needs the `.dSYM` files to be moved to the device
 
 // FIXME(#117097): backtrace (possibly unwinding mechanism) seems to be different on at least
 // `i686-mingw` (32-bit windows-gnu)? cc #128911.
diff --git a/tests/ui/runtime/on-broken-pipe/child-processes.rs b/tests/ui/runtime/on-broken-pipe/child-processes.rs
index c0c8ad4e2f5..b7022e1b09d 100644
--- a/tests/ui/runtime/on-broken-pipe/child-processes.rs
+++ b/tests/ui/runtime/on-broken-pipe/child-processes.rs
@@ -1,5 +1,6 @@
 //@ revisions: default error kill inherit
 //@ ignore-cross-compile because aux-bin does not yet support it
+//@ ignore-remote because aux-bin does not yet support it
 //@ only-unix because SIGPIPE is a unix thing
 //@ ignore-backends: gcc
 //@ run-pass
diff --git a/tests/ui/runtime/on-broken-pipe/inherit.rs b/tests/ui/runtime/on-broken-pipe/inherit.rs
index f3c8140eaae..e99c7c7a0fe 100644
--- a/tests/ui/runtime/on-broken-pipe/inherit.rs
+++ b/tests/ui/runtime/on-broken-pipe/inherit.rs
@@ -1,4 +1,5 @@
 //@ ignore-cross-compile because aux-bin does not yet support it
+//@ ignore-remote because aux-bin does not yet support it
 //@ only-unix because SIGPIPE is a unix thing
 //@ aux-bin: assert-inherit-sig_dfl.rs
 //@ aux-bin: assert-inherit-sig_ign.rs