Add /System/iOSSupport to the library search path on Mac Catalyst

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2997,6 +2997,16 @@ fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
         }
         _ => unreachable!(),
     }
+
+    if llvm_target.contains("macabi") {
+        // Mac Catalyst uses the macOS SDK, but to link to iOS-specific
+        // frameworks, we must have the support library stubs in the library
+        // search path.
+
+        // The flags are called `-L` and `-F` both in Clang, ld64 and ldd.
+        cmd.arg(format!("-L{sdk_root}/System/iOSSupport/usr/lib"));
+        cmd.arg(format!("-F{sdk_root}/System/iOSSupport/System/Library/Frameworks"));
+    }
 }
 
 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, errors::AppleSdkRootError<'_>> {

src/tools/compiletest/src/header.rs

@@ -790,15 +790,18 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "ignore-thumb",
     "ignore-thumbv8m.base-none-eabi",
     "ignore-thumbv8m.main-none-eabi",
+    "ignore-tvos",
     "ignore-unix",
     "ignore-unknown",
     "ignore-uwp",
+    "ignore-visionos",
     "ignore-vxworks",
     "ignore-wasi",
     "ignore-wasm",
     "ignore-wasm32",
     "ignore-wasm32-bare",
     "ignore-wasm64",
+    "ignore-watchos",
     "ignore-windows",
     "ignore-windows-gnu",
     "ignore-x32",
@@ -856,6 +859,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "only-cdb",
     "only-gnu",
     "only-i686-pc-windows-msvc",
+    "only-ios",
     "only-linux",
     "only-loongarch64",
     "only-loongarch64-unknown-linux-gnu",
@@ -871,10 +875,13 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "only-sparc64",
     "only-stable",
     "only-thumb",
+    "only-tvos",
     "only-unix",
+    "only-visionos",
     "only-wasm32",
     "only-wasm32-bare",
     "only-wasm32-wasip1",
+    "only-watchos",
     "only-windows",
     "only-x86",
     "only-x86_64",

tests/ui/linkage-attr/uikit-framework.rs

@@ -0,0 +1,25 @@
+//! Check that linking to UIKit on platforms where that is available works.
+//@ revisions: ios tvos watchos visionos
+//@ [ios]only-ios
+//@ [tvos]only-tvos
+//@ [watchos]only-watchos
+//@ [visionos]only-visionos
+//@ build-pass
+
+use std::ffi::{c_char, c_int, c_void};
+
+#[link(name = "UIKit", kind = "framework")]
+extern "C" {
+    pub fn UIApplicationMain(
+        argc: c_int,
+        argv: *const c_char,
+        principalClassName: *const c_void,
+        delegateClassName: *const c_void,
+    ) -> c_int;
+}
+
+pub fn main() {
+    unsafe {
+        UIApplicationMain(0, core::ptr::null(), core::ptr::null(), core::ptr::null());
+    }
+}