src/tools/run-make-support/src/external_deps/rustc.rs

@@ -6,7 +6,7 @@ use crate::command::Command;
 use crate::env::env_var;
 use crate::path_helpers::cwd;
 use crate::util::set_host_compiler_dylib_path;
-use crate::{is_aix, is_darwin, is_msvc, is_windows, uname};
+use crate::{is_aix, is_darwin, is_msvc, is_windows, target, uname};
 
 /// Construct a new `rustc` invocation. This will automatically set the library
 /// search path as `-L cwd()`. Use [`bare_rustc`] to avoid this.
@@ -33,9 +33,15 @@ pub fn aux_build() -> Rustc {
 #[must_use]
 pub struct Rustc {
     cmd: Command,
+    target: Option<String>,
 }
 
-crate::macros::impl_common_helpers!(Rustc);
+/// Only fill in the target just before execution, so that it can be overridden.
+crate::macros::impl_common_helpers!(Rustc, |rustc: &mut Rustc| {
+    if let Some(target) = &rustc.target {
+        rustc.cmd.arg(&format!("--target={target}"));
+    }
+});
 
 pub fn rustc_path() -> String {
     env_var("RUSTC")
@@ -52,27 +58,30 @@ impl Rustc {
     // `rustc` invocation constructor methods
 
     /// Construct a new `rustc` invocation. This will automatically set the library
-    /// search path as `-L cwd()`. Use [`bare_rustc`] to avoid this.
+    /// search path as `-L cwd()` and also the compilation target.
+    /// Use [`bare_rustc`] to avoid this.
     #[track_caller]
     pub fn new() -> Self {
         let mut cmd = setup_common();
         cmd.arg("-L").arg(cwd());
-        Self { cmd }
+
+        // Automatically default to cross-compilation
+        Self { cmd, target: Some(target()) }
     }
 
     /// Construct a bare `rustc` invocation with no flags set.
     #[track_caller]
     pub fn bare() -> Self {
         let cmd = setup_common();
-        Self { cmd }
+        Self { cmd, target: None }
     }
 
     /// Construct a new `rustc` invocation with `aux_build` preset (setting `--crate-type=lib`).
     #[track_caller]
     pub fn new_aux_build() -> Self {
         let mut cmd = setup_common();
         cmd.arg("--crate-type=lib");
-        Self { cmd }
+        Self { cmd, target: None }
     }
 
     // Argument provider methods
@@ -248,8 +257,9 @@ impl Rustc {
 
     /// Specify the target triple, or a path to a custom target json spec file.
     pub fn target<S: AsRef<str>>(&mut self, target: S) -> &mut Self {
-        let target = target.as_ref();
-        self.cmd.arg(format!("--target={target}"));
+        // We store the target as a separate field, so that it can be specified multiple times.
+        // This is in particular useful to override the default target set in Rustc::new().
+        self.target = Some(target.as_ref().to_string());
         self
     }
 

src/tools/run-make-support/src/macros.rs

@@ -23,10 +23,16 @@
 /// }
 /// ```
 ///
+/// You can pass an optional second parameter which should be a function that is passed
+/// `&mut self` just before the command is executed.
+///
 /// [`Command`]: crate::command::Command
 /// [`CompletedProcess`]: crate::command::CompletedProcess
 macro_rules! impl_common_helpers {
     ($wrapper: ident) => {
+        $crate::macros::impl_common_helpers!($wrapper, |_| {});
+    };
+    ($wrapper: ident, $before_exec: expr) => {
         impl $wrapper {
             /// Specify an environment variable.
             pub fn env<K, V>(&mut self, key: K, value: V) -> &mut Self
@@ -118,12 +124,14 @@ macro_rules! impl_common_helpers {
             /// Run the constructed command and assert that it is successfully run.
             #[track_caller]
             pub fn run(&mut self) -> crate::command::CompletedProcess {
+                $before_exec(&mut *self);
                 self.cmd.run()
             }
 
             /// Run the constructed command and assert that it does not successfully run.
             #[track_caller]
             pub fn run_fail(&mut self) -> crate::command::CompletedProcess {
+                $before_exec(&mut *self);
                 self.cmd.run_fail()
             }
 
@@ -133,6 +141,7 @@ macro_rules! impl_common_helpers {
             /// whenever possible.
             #[track_caller]
             pub fn run_unchecked(&mut self) -> crate::command::CompletedProcess {
+                $before_exec(&mut *self);
                 self.cmd.run_unchecked()
             }
 

tests/run-make/apple-deployment-target/rmake.rs

@@ -41,7 +41,6 @@ fn main() {
 
     // Remove env vars to get `rustc`'s default
     let output = rustc()
-        .target(target())
         .env_remove("MACOSX_DEPLOYMENT_TARGET")
         .env_remove("IPHONEOS_DEPLOYMENT_TARGET")
         .env_remove("WATCHOS_DEPLOYMENT_TARGET")
@@ -58,7 +57,6 @@ fn main() {
     run_in_tmpdir(|| {
         let rustc = || {
             let mut rustc = rustc();
-            rustc.target(target());
             rustc.crate_type("lib");
             rustc.emit("obj");
             rustc.input("foo.rs");
@@ -82,7 +80,6 @@ fn main() {
 
         let rustc = || {
             let mut rustc = rustc();
-            rustc.target(target());
             rustc.crate_type("dylib");
             rustc.input("foo.rs");
             rustc.output("libfoo.dylib");
@@ -108,7 +105,6 @@ fn main() {
     run_in_tmpdir(|| {
         let rustc = || {
             let mut rustc = rustc();
-            rustc.target(target());
             rustc.crate_type("bin");
             rustc.input("foo.rs");
             rustc.output("foo");
@@ -147,7 +143,6 @@ fn main() {
     run_in_tmpdir(|| {
         let rustc = || {
             let mut rustc = rustc();
-            rustc.target(target());
             rustc.incremental("incremental");
             rustc.crate_type("lib");
             rustc.emit("obj");

tests/run-make/apple-sdk-version/rmake.rs

@@ -24,8 +24,7 @@ fn has_sdk_version(file: &str, version: &str) {
 
 fn main() {
     // Fetch rustc's inferred deployment target.
-    let current_deployment_target =
-        rustc().target(target()).print("deployment-target").run().stdout_utf8();
+    let current_deployment_target = rustc().print("deployment-target").run().stdout_utf8();
     let current_deployment_target = current_deployment_target.split('=').last().unwrap().trim();
 
     // Fetch current SDK version via. xcrun.
@@ -45,15 +44,15 @@ fn main() {
     let current_sdk_version = current_sdk_version.trim();
 
     // Check the SDK version in the object file produced by the codegen backend.
-    rustc().target(target()).crate_type("lib").emit("obj").input("foo.rs").output("foo.o").run();
+    rustc().crate_type("lib").emit("obj").input("foo.rs").output("foo.o").run();
     // Set to 0, which means not set or "n/a".
     has_sdk_version("foo.o", "n/a");
 
     // Check the SDK version in the .rmeta file, as set in `create_object_file`.
     //
     // This is just to ensure that we don't set some odd version in `create_object_file`,
     // if the rmeta file is packed in a different way in the future, this can safely be removed.
-    rustc().target(target()).crate_type("rlib").input("foo.rs").output("libfoo.rlib").run();
+    rustc().crate_type("rlib").input("foo.rs").output("libfoo.rlib").run();
     // Extra .rmeta file (which is encoded as an object file).
     cmd("ar").arg("-x").arg("libfoo.rlib").arg("lib.rmeta").run();
     has_sdk_version("lib.rmeta", "n/a");
@@ -69,7 +68,6 @@ fn main() {
         // Test with clang
         let file_name = format!("foo_cc{file_ext}");
         rustc()
-            .target(target())
             .crate_type("bin")
             .arg("-Clinker-flavor=gcc")
             .input("foo.rs")
@@ -80,7 +78,6 @@ fn main() {
         // Test with ld64
         let file_name = format!("foo_ld{file_ext}");
         rustc()
-            .target(target())
             .crate_type("bin")
             .arg("-Clinker-flavor=ld")
             .input("foo.rs")

tests/run-make/mte-ffi/rmake.rs

@@ -22,11 +22,7 @@ fn run_test(variant: &str) {
         flags
     };
     println!("{variant} test...");
-    rustc()
-        .input(format!("foo_{variant}.rs"))
-        .target(target())
-        .linker("aarch64-linux-gnu-gcc")
-        .run();
+    rustc().input(format!("foo_{variant}.rs")).linker("aarch64-linux-gnu-gcc").run();
     gcc()
         .input(format!("bar_{variant}.c"))
         .input(dynamic_lib_name("foo"))

tests/run-make/rustc-macro-dep-files/rmake.rs

@@ -8,7 +8,7 @@ use run_make_support::{diff, rustc, target};
 
 fn main() {
     rustc().input("foo.rs").run();
-    rustc().input("bar.rs").target(target()).emit("dep-info").run();
+    rustc().input("bar.rs").emit("dep-info").run();
     // The emitted file should not contain "proc-macro source".
     diff().expected_file("correct.d").actual_file("bar.d").run();
 }

tests/run-make/static-pie/rmake.rs

@@ -49,7 +49,6 @@ fn test(compiler: &str) {
 
     rustc()
         .input("test-aslr.rs")
-        .target(target())
         .linker(compiler)
         .arg("-Clinker-flavor=gcc")
         .arg("-Ctarget-feature=+crt-static")

tests/run-make/sysroot-crates-are-unstable/rmake.rs

@@ -31,7 +31,6 @@ fn check_crate_is_unstable(cr: &Crate) {
     // Trying to use this crate from a user program should fail.
     let output = rustc()
         .crate_type("rlib")
-        .target(target())
         .extern_(name, path)
         .input("-")
         .stdin_buf(format!("extern crate {name};"))