Rollup merge of #77202 - ehuss:defer-apple-sdkroot, r=petrochenkov

Defer Apple SDKROOT detection to link time.

This defers the detection of the SDKROOT for Apple iOS/tvOS targets to link time, instead of when the `Target` is defined. This allows commands that don't need to link to work (like `rustdoc` or `rustc --print=target-list`). This also makes `--print=target-list` a bit faster.

This also removes the note in the platform support documentation about these targets being missing. When I wrote it, I misunderstood how the SDKROOT stuff worked.

Notes:
* This means that JSON spec targets can't explicitly override these flags. I think that is probably fine, as I believe the value is generally required, and can be set with the SDKROOT environment variable.
* This changes `x86_64-apple-tvos` to use `appletvsimulator`. I think the original code was wrong (it was using `iphonesimulator`). Also, `x86_64-apple-tvos` seems broken in general, and I cannot build it locally. The `data_layout` does not appear to be correct (it is a copy of the arm64 layout instead of the x86_64 layout). I have not tried building Apple's LLVM to see if that helps, but I suspect it is just wrong (I'm uncertain since I don't know how the tvOS simulator works with its bitcode-only requirements).
* I'm tempted to remove the use of `Result` for built-in target definitions, since I don't think they should be fallible. This was added in https://github.com/rust-lang/rust/pull/34980, but that only relates to JSON definitions. I think the built-in targets shouldn't fail. I can do this now, or not.

Fixes #36156
Fixes #76584

10 files changed, 106 insertions, 128 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 87d539f748c..010fd4e9c5a 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -1524,6 +1524,9 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
     // NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
     add_pre_link_args(cmd, sess, flavor);
 
+    // NO-OPT-OUT, OBJECT-FILES-NO
+    add_apple_sdk(cmd, sess, flavor);
+
     // NO-OPT-OUT
     add_link_script(cmd, sess, tmpdir, crate_type);
 
@@ -2083,3 +2086,86 @@ fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
         config::Lto::No | config::Lto::ThinLocal => false,
     }
 }
+
+fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
+    let arch = &sess.target.target.arch;
+    let os = &sess.target.target.target_os;
+    let llvm_target = &sess.target.target.llvm_target;
+    if sess.target.target.target_vendor != "apple"
+        || !matches!(os.as_str(), "ios" | "tvos")
+        || flavor != LinkerFlavor::Gcc
+    {
+        return;
+    }
+    let sdk_name = match (arch.as_str(), os.as_str()) {
+        ("aarch64", "tvos") => "appletvos",
+        ("x86_64", "tvos") => "appletvsimulator",
+        ("arm", "ios") => "iphoneos",
+        ("aarch64", "ios") => "iphoneos",
+        ("x86", "ios") => "iphonesimulator",
+        ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx10.15",
+        ("x86_64", "ios") => "iphonesimulator",
+        _ => {
+            sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
+            return;
+        }
+    };
+    let sdk_root = match get_apple_sdk_root(sdk_name) {
+        Ok(s) => s,
+        Err(e) => {
+            sess.err(&e);
+            return;
+        }
+    };
+    let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
+    cmd.args(&["-arch", arch_name, "-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
+}
+
+fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
+    // Following what clang does
+    // (https://github.com/llvm/llvm-project/blob/
+    // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
+    // to allow the SDK path to be set. (For clang, xcrun sets
+    // SDKROOT; for rustc, the user or build system can set it, or we
+    // can fall back to checking for xcrun on PATH.)
+    if let Ok(sdkroot) = env::var("SDKROOT") {
+        let p = Path::new(&sdkroot);
+        match sdk_name {
+            // Ignore `SDKROOT` if it's clearly set for the wrong platform.
+            "appletvos"
+                if sdkroot.contains("TVSimulator.platform")
+                    || sdkroot.contains("MacOSX.platform") => {}
+            "appletvsimulator"
+                if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
+            "iphoneos"
+                if sdkroot.contains("iPhoneSimulator.platform")
+                    || sdkroot.contains("MacOSX.platform") => {}
+            "iphonesimulator"
+                if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
+            }
+            "macosx10.15"
+                if sdkroot.contains("iPhoneOS.platform")
+                    || sdkroot.contains("iPhoneSimulator.platform") => {}
+            // Ignore `SDKROOT` if it's not a valid path.
+            _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
+            _ => return Ok(sdkroot),
+        }
+    }
+    let res =
+        Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
+            |output| {
+                if output.status.success() {
+                    Ok(String::from_utf8(output.stdout).unwrap())
+                } else {
+                    let error = String::from_utf8(output.stderr);
+                    let error = format!("process exit with error: {}", error.unwrap());
+                    Err(io::Error::new(io::ErrorKind::Other, &error[..]))
+                }
+            },
+        );
+
+    match res {
+        Ok(output) => Ok(output.trim().to_string()),
+        Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),
+    }
+}
diff --git a/compiler/rustc_target/src/spec/aarch64_apple_ios.rs b/compiler/rustc_target/src/spec/aarch64_apple_ios.rs
index 21dcec8d5e3..168cd01878e 100644
--- a/compiler/rustc_target/src/spec/aarch64_apple_ios.rs
+++ b/compiler/rustc_target/src/spec/aarch64_apple_ios.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::Arm64, AppleOS::iOS)?;
+    let base = opts(Arch::Arm64);
     Ok(Target {
         llvm_target: "arm64-apple-ios".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/aarch64_apple_tvos.rs b/compiler/rustc_target/src/spec/aarch64_apple_tvos.rs
index 2b0cd6cabf8..5e2cab0df1e 100644
--- a/compiler/rustc_target/src/spec/aarch64_apple_tvos.rs
+++ b/compiler/rustc_target/src/spec/aarch64_apple_tvos.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::Arm64, AppleOS::tvOS)?;
+    let base = opts(Arch::Arm64);
     Ok(Target {
         llvm_target: "arm64-apple-tvos".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/apple_sdk_base.rs b/compiler/rustc_target/src/spec/apple_sdk_base.rs
index 0d0a0da9d1c..e34277d5af0 100644
--- a/compiler/rustc_target/src/spec/apple_sdk_base.rs
+++ b/compiler/rustc_target/src/spec/apple_sdk_base.rs
@@ -1,8 +1,4 @@
-use crate::spec::{LinkArgs, LinkerFlavor, TargetOptions};
-use std::env;
-use std::io;
-use std::path::Path;
-use std::process::Command;
+use crate::spec::TargetOptions;
 
 use Arch::*;
 #[allow(non_camel_case_types)]
@@ -16,108 +12,6 @@ pub enum Arch {
     X86_64_macabi,
 }
 
-#[allow(non_camel_case_types)]
-#[derive(Copy, Clone)]
-pub enum AppleOS {
-    tvOS,
-    iOS,
-}
-
-impl Arch {
-    pub fn to_string(self) -> &'static str {
-        match self {
-            Armv7 => "armv7",
-            Armv7s => "armv7s",
-            Arm64 => "arm64",
-            I386 => "i386",
-            X86_64 => "x86_64",
-            X86_64_macabi => "x86_64",
-        }
-    }
-}
-
-pub fn get_sdk_root(sdk_name: &str) -> Result<String, String> {
-    // Following what clang does
-    // (https://github.com/llvm/llvm-project/blob/
-    // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
-    // to allow the SDK path to be set. (For clang, xcrun sets
-    // SDKROOT; for rustc, the user or build system can set it, or we
-    // can fall back to checking for xcrun on PATH.)
-    if let Ok(sdkroot) = env::var("SDKROOT") {
-        let p = Path::new(&sdkroot);
-        match sdk_name {
-            // Ignore `SDKROOT` if it's clearly set for the wrong platform.
-            "appletvos"
-                if sdkroot.contains("TVSimulator.platform")
-                    || sdkroot.contains("MacOSX.platform") => {}
-            "appletvsimulator"
-                if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
-            "iphoneos"
-                if sdkroot.contains("iPhoneSimulator.platform")
-                    || sdkroot.contains("MacOSX.platform") => {}
-            "iphonesimulator"
-                if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
-            }
-            "macosx10.15"
-                if sdkroot.contains("iPhoneOS.platform")
-                    || sdkroot.contains("iPhoneSimulator.platform") => {}
-            // Ignore `SDKROOT` if it's not a valid path.
-            _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
-            _ => return Ok(sdkroot),
-        }
-    }
-    let res =
-        Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
-            |output| {
-                if output.status.success() {
-                    Ok(String::from_utf8(output.stdout).unwrap())
-                } else {
-                    let error = String::from_utf8(output.stderr);
-                    let error = format!("process exit with error: {}", error.unwrap());
-                    Err(io::Error::new(io::ErrorKind::Other, &error[..]))
-                }
-            },
-        );
-
-    match res {
-        Ok(output) => Ok(output.trim().to_string()),
-        Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),
-    }
-}
-
-fn build_pre_link_args(arch: Arch, os: AppleOS) -> Result<LinkArgs, String> {
-    let sdk_name = match (arch, os) {
-        (Arm64, AppleOS::tvOS) => "appletvos",
-        (X86_64, AppleOS::tvOS) => "appletvsimulator",
-        (Armv7, AppleOS::iOS) => "iphoneos",
-        (Armv7s, AppleOS::iOS) => "iphoneos",
-        (Arm64, AppleOS::iOS) => "iphoneos",
-        (I386, AppleOS::iOS) => "iphonesimulator",
-        (X86_64, AppleOS::iOS) => "iphonesimulator",
-        (X86_64_macabi, AppleOS::iOS) => "macosx10.15",
-        _ => unreachable!(),
-    };
-
-    let arch_name = arch.to_string();
-
-    let sdk_root = get_sdk_root(sdk_name)?;
-
-    let mut args = LinkArgs::new();
-    args.insert(
-        LinkerFlavor::Gcc,
-        vec![
-            "-arch".to_string(),
-            arch_name.to_string(),
-            "-isysroot".to_string(),
-            sdk_root.clone(),
-            "-Wl,-syslibroot".to_string(),
-            sdk_root,
-        ],
-    );
-
-    Ok(args)
-}
-
 fn target_cpu(arch: Arch) -> String {
     match arch {
         Armv7 => "cortex-a8", // iOS7 is supported on iPhone 4 and higher
@@ -137,15 +31,13 @@ fn link_env_remove(arch: Arch) -> Vec<String> {
     }
 }
 
-pub fn opts(arch: Arch, os: AppleOS) -> Result<TargetOptions, String> {
-    let pre_link_args = build_pre_link_args(arch, os)?;
-    Ok(TargetOptions {
+pub fn opts(arch: Arch) -> TargetOptions {
+    TargetOptions {
         cpu: target_cpu(arch),
         executables: true,
-        pre_link_args,
         link_env_remove: link_env_remove(arch),
         has_elf_tls: false,
         eliminate_frame_pointer: false,
         ..super::apple_base::opts()
-    })
+    }
 }
diff --git a/compiler/rustc_target/src/spec/armv7_apple_ios.rs b/compiler/rustc_target/src/spec/armv7_apple_ios.rs
index 393843526a8..6dafcc2c345 100644
--- a/compiler/rustc_target/src/spec/armv7_apple_ios.rs
+++ b/compiler/rustc_target/src/spec/armv7_apple_ios.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::Armv7, AppleOS::iOS)?;
+    let base = opts(Arch::Armv7);
     Ok(Target {
         llvm_target: "armv7-apple-ios".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/armv7s_apple_ios.rs b/compiler/rustc_target/src/spec/armv7s_apple_ios.rs
index 998a7b2e164..d6c99c4ade6 100644
--- a/compiler/rustc_target/src/spec/armv7s_apple_ios.rs
+++ b/compiler/rustc_target/src/spec/armv7s_apple_ios.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::Armv7s, AppleOS::iOS)?;
+    let base = opts(Arch::Armv7s);
     Ok(Target {
         llvm_target: "armv7s-apple-ios".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/i386_apple_ios.rs b/compiler/rustc_target/src/spec/i386_apple_ios.rs
index a121d49769d..6cb209ab1c0 100644
--- a/compiler/rustc_target/src/spec/i386_apple_ios.rs
+++ b/compiler/rustc_target/src/spec/i386_apple_ios.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::I386, AppleOS::iOS)?;
+    let base = opts(Arch::I386);
     Ok(Target {
         llvm_target: "i386-apple-ios".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/x86_64_apple_ios.rs b/compiler/rustc_target/src/spec/x86_64_apple_ios.rs
index cfcf856836b..fd3e4e2f57b 100644
--- a/compiler/rustc_target/src/spec/x86_64_apple_ios.rs
+++ b/compiler/rustc_target/src/spec/x86_64_apple_ios.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::X86_64, AppleOS::iOS)?;
+    let base = opts(Arch::X86_64);
     Ok(Target {
         llvm_target: "x86_64-apple-ios".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/x86_64_apple_ios_macabi.rs b/compiler/rustc_target/src/spec/x86_64_apple_ios_macabi.rs
index c42d0911725..4cfbd9eba06 100644
--- a/compiler/rustc_target/src/spec/x86_64_apple_ios_macabi.rs
+++ b/compiler/rustc_target/src/spec/x86_64_apple_ios_macabi.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::X86_64_macabi, AppleOS::iOS)?;
+    let base = opts(Arch::X86_64_macabi);
     Ok(Target {
         llvm_target: "x86_64-apple-ios13.0-macabi".to_string(),
         target_endian: "little".to_string(),
diff --git a/compiler/rustc_target/src/spec/x86_64_apple_tvos.rs b/compiler/rustc_target/src/spec/x86_64_apple_tvos.rs
index a56062c0b2b..664a3ed8816 100644
--- a/compiler/rustc_target/src/spec/x86_64_apple_tvos.rs
+++ b/compiler/rustc_target/src/spec/x86_64_apple_tvos.rs
@@ -1,8 +1,8 @@
-use super::apple_sdk_base::{opts, AppleOS, Arch};
+use super::apple_sdk_base::{opts, Arch};
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let base = opts(Arch::X86_64, AppleOS::iOS)?;
+    let base = opts(Arch::X86_64);
     Ok(Target {
         llvm_target: "x86_64-apple-tvos".to_string(),
         target_endian: "little".to_string(),