Add a test for Mach-O #[link_section] API inherited from LLVM

tests/run-make/macho-link-section/foo.rs

@@ -0,0 +1,14 @@
+#[unsafe(no_mangle)]
+#[unsafe(link_section = "__TEXT,custom_code,regular,pure_instructions")]
+static CODE: [u8; 10] = *b"0123456789";
+
+#[unsafe(no_mangle)]
+#[unsafe(link_section = "__DATA,all_attributes,regular,pure_instructions\
+                        +no_toc+strip_static_syms+no_dead_strip+live_support\
+                        +self_modifying_code+debug")]
+static ALL_THE_ATTRIBUTES: u32 = 42;
+
+#[unsafe(no_mangle)]
+#[unsafe(link_section = "__DATA,__mod_init_func,mod_init_funcs")]
+static CONSTRUCTOR: extern "C" fn() = constructor;
+extern "C" fn constructor() {}

tests/run-make/macho-link-section/rmake.rs

@@ -0,0 +1,47 @@
+//! Test that various Mach-O `#[link_section]` values are parsed and passed on correctly by codegen
+//! backends.
+//@ only-apple
+use run_make_support::{llvm_objdump, rustc};
+
+fn main() {
+    rustc().input("foo.rs").crate_type("lib").arg("--emit=obj").run();
+
+    let stdout =
+        llvm_objdump().arg("--macho").arg("--private-headers").input("foo.o").run().stdout_utf8();
+
+    let expected = [
+        ("__TEXT", "custom_code", "S_REGULAR", "PURE_INSTRUCTIONS"),
+        ("__DATA", "__mod_init_func", "S_MOD_INIT_FUNC_POINTERS", "(none)"),
+        (
+            "__DATA",
+            "all_attributes",
+            "S_REGULAR",
+            "PURE_INSTRUCTIONS NO_TOC STRIP_STATIC_SYMS \
+             NO_DEAD_STRIP LIVE_SUPPORT SELF_MODIFYING_CODE DEBUG",
+        ),
+    ];
+
+    for (segment, section, section_type, section_attributes) in expected {
+        let mut found = false;
+        // Skip header.
+        for section_info in stdout.split("Section").skip(1) {
+            if section_info.contains(&format!("segname {segment}"))
+                && section_info.contains(&format!("sectname {section}"))
+            {
+                assert!(
+                    section_info.contains(&format!("type {section_type}")),
+                    "should have type {section_type:?}"
+                );
+                assert!(
+                    section_info.contains(&format!("attributes {section_attributes}\n")),
+                    "should have attributes {section_attributes:?}"
+                );
+                found = true;
+            }
+        }
+
+        if !found {
+            panic!("could not find section {section} in binary");
+        }
+    }
+}