fix macho section specifier & windows test

Author: folkertdev

compiler/rustc_codegen_ssa/src/mir/naked_asm.rs

@@ -295,7 +295,8 @@ fn prefix_and_suffix<'tcx>(
             if let Some(section) = &link_section {
                 writeln!(begin, ".section {section},\"xr\"").unwrap()
             } else if !function_sections {
-                // Function sections are enabled by default on MSVC, but disabled by default on GNU.
+                // Function sections are enabled by default on MSVC and windows-gnullvm,
+                // but disabled by default on GNU.
                 writeln!(begin, ".text").unwrap();
             } else {
                 // LLVM uses an extension to the section directive to support defining multiple

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

@@ -449,6 +449,16 @@ impl Rustc {
         self.cmd.arg("-Zcodegen-source-order");
         self
     }
+
+    /// Specify `-Z function-sections={yes, no}`.
+    pub fn function_sections(&mut self, enable: bool) -> &mut Self {
+        let flag = match enable {
+            true => "-Zfunction-sections=yes",
+            false => "-Zfunction-sections=no",
+        };
+        self.cmd.arg(flag);
+        self
+    }
 }
 
 /// Query the sysroot path corresponding `rustc --print=sysroot`.

tests/run-make/naked-dead-code-elimination/main.rs

@@ -1,3 +1,4 @@
+#![feature(cfg_target_object_format)]
 use std::arch::naked_asm;
 
 #[unsafe(naked)]
@@ -6,19 +7,36 @@ extern "C" fn used() {
     naked_asm!("ret")
 }
 
+#[unsafe(no_mangle)]
+extern "C" fn unused_clothed() -> i32 {
+    42
+}
+
 #[unsafe(naked)]
 #[unsafe(no_mangle)]
 extern "C" fn unused() {
     naked_asm!("ret")
 }
 
 #[unsafe(naked)]
-#[unsafe(link_section = "foobar")]
+#[unsafe(link_section = cfg_select!(
+    target_object_format = "mach-o" => "__TEXT,foobar",
+    _ => ".foobar",
+))]
 #[unsafe(no_mangle)]
 extern "C" fn unused_link_section() {
     naked_asm!("ret")
 }
 
+#[unsafe(link_section = cfg_select!(
+    target_object_format = "mach-o" => "__TEXT,baz",
+    _ => ".baz",
+))]
+#[unsafe(no_mangle)]
+extern "C" fn unused_link_section_clothed() -> i32 {
+    43
+}
+
 fn main() {
     used();
 }

tests/run-make/naked-dead-code-elimination/rmake.rs

@@ -4,7 +4,19 @@ use run_make_support::symbols::object_contains_any_symbol;
 use run_make_support::{bin_name, rustc};
 
 fn main() {
-    rustc().input("main.rs").opt().run();
-    let mut unused = vec!["unused", "unused_link_section"];
-    assert!(!object_contains_any_symbol(bin_name("main"), &unused));
+    rustc().input("main.rs").opt().function_sections(true).run();
+
+    let bin = bin_name("main");
+
+    // Check that the naked symbol is eliminated when the "clothed" one is.
+
+    assert_eq!(
+        object_contains_any_symbol(&bin, &["unused_clothed"]),
+        object_contains_any_symbol(&bin, &["unused"])
+    );
+
+    assert_eq!(
+        object_contains_any_symbol(&bin, &["unused_link_section_clothed"]),
+        object_contains_any_symbol(&bin, &["unused_link_section"])
+    );
 }