Fix cross-compilation to macOS

4 files changed, 62 insertions, 50 deletions

diff --git a/src/librustc_target/spec/apple_base.rs b/src/librustc_target/spec/apple_base.rs
index 297e64d4aeb..a8d6290aa43 100644
--- a/src/librustc_target/spec/apple_base.rs
+++ b/src/librustc_target/spec/apple_base.rs
@@ -1,4 +1,4 @@
-use std::{env, io, path::Path, process::Command};
+use std::{env, path::Path};
 
 use crate::spec::{LinkArgs, TargetOptions};
 
@@ -52,18 +52,19 @@ pub fn macos_llvm_target(arch: &str) -> String {
     format!("{}-apple-macosx{}.{}.0", arch, major, minor)
 }
 
-pub fn sysroot(sdk: &str) -> Result<String, String> {
-    let actual_sdk_path = sdk_path(sdk)?;
+#[cfg(target_os = "macos")]
+pub fn sysroot(sdk: &str) -> Result<Option<String>, String> {
     // Like Clang, allow the `SDKROOT` environment variable used by Xcode to define the sysroot.
     if let Some(sdk_root) = env::var("SDKROOT").ok() {
+        let actual_sdk_path = sdk_path(sdk)?;
         let sdk_root_p = Path::new(&sdk_root);
         // Ignore `SDKROOT` if it's not a valid path.
         if !sdk_root_p.is_absolute() || sdk_root_p == Path::new("/") || !sdk_root_p.exists() {
-            return Ok(actual_sdk_path);
+            return Ok(Some(actual_sdk_path));
         }
         // Ignore `SDKROOT` if it's clearly set for the wrong platform, which may occur when we're
         // compiling a custom build script while targeting iOS for example.
-        return Ok(match sdk {
+        return Ok(Some(match sdk {
             "iphoneos" if sdk_root.contains("iPhoneSimulator.platform")
                 || sdk_root.contains("MacOSX.platform") => actual_sdk_path,
             "iphonesimulator" if sdk_root.contains("iPhoneOS.platform")
@@ -71,24 +72,40 @@ pub fn sysroot(sdk: &str) -> Result<String, String> {
             "macosx" | "macosx10.15" if sdk_root.contains("iPhoneOS.platform")
                 || sdk_root.contains("iPhoneSimulator.platform") => actual_sdk_path,
             _ => sdk_root,
-        })
+        }))
     }
-    Ok(actual_sdk_path)
+    Ok(None)
 }
 
+// `xcrun` is only available on macOS.
+#[cfg(not(target_os = "macos"))]
+pub fn sysroot(_sdk: &str) -> Result<Option<String>, String> {
+    if let Some(sdk_root) = env::var("SDKROOT").ok() {
+        let sdk_root_p = Path::new(&sdk_root);
+        // Use `SDKROOT` only if it's a valid path.
+        if sdk_root_p.is_absolute() && sdk_root_p != Path::new("/") && sdk_root_p.exists() {
+            return Ok(Some(sdk_root));
+        }
+    }
+    Ok(None)
+}
+
+#[cfg(target_os = "macos")]
 fn sdk_path(sdk_name: &str) -> Result<String, String> {
-    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[..]))
-                }
-            },
-        );
+    let res = std::process::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(std::io::Error::new(std::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/src/librustc_target/spec/apple_ios_base.rs b/src/librustc_target/spec/apple_ios_base.rs
index db4a8180831..801736944f4 100644
--- a/src/librustc_target/spec/apple_ios_base.rs
+++ b/src/librustc_target/spec/apple_ios_base.rs
@@ -35,16 +35,19 @@ fn build_pre_link_args(arch: Arch) -> Result<LinkArgs, String> {
 
     let arch_name = arch.to_string();
 
-    let sdk_root = super::apple_base::sysroot(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]);
+    args.insert(LinkerFlavor::Gcc, vec!["-arch".to_string(), arch_name.to_string()]);
+    if let Some(sdk_root) = super::apple_base::sysroot(sdk_name)? {
+        args.insert(
+            LinkerFlavor::Gcc,
+            vec![
+                "-isysroot".to_string(),
+                sdk_root.clone(),
+                "-Wl,-syslibroot".to_string(),
+                sdk_root
+            ],
+        );
+    }
 
     Ok(args)
 }
diff --git a/src/librustc_target/spec/i686_apple_darwin.rs b/src/librustc_target/spec/i686_apple_darwin.rs
index a60c0072124..b08ed560252 100644
--- a/src/librustc_target/spec/i686_apple_darwin.rs
+++ b/src/librustc_target/spec/i686_apple_darwin.rs
@@ -1,20 +1,16 @@
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let sysroot = super::apple_base::sysroot("macosx")?;
     let mut base = super::apple_base::opts();
     base.cpu = "yonah".to_string();
     base.max_atomic_width = Some(64);
-    base.pre_link_args.insert(
-        LinkerFlavor::Gcc,
-        vec![
-            "-m32".to_string(),
-            "-isysroot".to_string(),
-            sysroot.clone(),
-            "-Wl,-syslibroot".to_string(),
-            sysroot,
-        ],
-    );
+    base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m32".to_string()]);
+    if let Some(sysroot) = super::apple_base::sysroot("macosx")? {
+        base.pre_link_args.insert(
+            LinkerFlavor::Gcc,
+            vec!["-isysroot".to_string(), sysroot.clone(), "-Wl,-syslibroot".to_string(), sysroot],
+        );
+    }
     base.stack_probes = true;
     base.eliminate_frame_pointer = false;
 
diff --git a/src/librustc_target/spec/x86_64_apple_darwin.rs b/src/librustc_target/spec/x86_64_apple_darwin.rs
index b72d037565b..f299c27e7e1 100644
--- a/src/librustc_target/spec/x86_64_apple_darwin.rs
+++ b/src/librustc_target/spec/x86_64_apple_darwin.rs
@@ -1,21 +1,17 @@
 use crate::spec::{LinkerFlavor, Target, TargetOptions, TargetResult};
 
 pub fn target() -> TargetResult {
-    let sysroot = super::apple_base::sysroot("macosx")?;
     let mut base = super::apple_base::opts();
     base.cpu = "core2".to_string();
     base.max_atomic_width = Some(128); // core2 support cmpxchg16b
     base.eliminate_frame_pointer = false;
-    base.pre_link_args.insert(
-        LinkerFlavor::Gcc,
-        vec![
-            "-m64".to_string(),
-            "-isysroot".to_string(),
-            sysroot.clone(),
-            "-Wl,-syslibroot".to_string(),
-            sysroot,
-        ],
-    );
+    base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m64".to_string()]);
+    if let Some(sysroot) = super::apple_base::sysroot("macosx")? {
+        base.pre_link_args.insert(
+            LinkerFlavor::Gcc,
+            vec!["-isysroot".to_string(), sysroot.clone(), "-Wl,-syslibroot".to_string(), sysroot],
+        );
+    }
     base.stack_probes = true;
 
     // Clang automatically chooses a more specific target based on