emit .weak_definition instead of .weak on macos

Author: folkertdev

compiler/rustc_codegen_ssa/src/mir/naked_asm.rs

@@ -153,16 +153,23 @@ fn prefix_and_suffix<'tcx>(
         ("", "")
     };
 
+    let asm_binary_format = AsmBinaryFormat::from_target(&tcx.sess.target);
+
+    let weak_directive = match asm_binary_format {
+        AsmBinaryFormat::Elf | AsmBinaryFormat::Coff => ".weak",
+        AsmBinaryFormat::Macho => ".weak_definition",
+    };
+
     let emit_fatal = |msg| tcx.dcx().span_fatal(tcx.def_span(instance.def_id()), msg);
 
     // see https://godbolt.org/z/cPK4sxKor.
     // None means the default, which corresponds to internal linkage
     let linkage = match item_data.linkage {
         Linkage::External => Some(".globl"),
-        Linkage::LinkOnceAny => Some(".weak"),
-        Linkage::LinkOnceODR => Some(".weak"),
-        Linkage::WeakAny => Some(".weak"),
-        Linkage::WeakODR => Some(".weak"),
+        Linkage::LinkOnceAny => Some(weak_directive),
+        Linkage::LinkOnceODR => Some(weak_directive),
+        Linkage::WeakAny => Some(weak_directive),
+        Linkage::WeakODR => Some(weak_directive),
         Linkage::Internal => None,
         Linkage::Private => None,
         Linkage::Appending => emit_fatal("Only global variables can have appending linkage!"),
@@ -179,7 +186,7 @@ fn prefix_and_suffix<'tcx>(
 
     let mut begin = String::new();
     let mut end = String::new();
-    match AsmBinaryFormat::from_target(&tcx.sess.target) {
+    match asm_binary_format {
         AsmBinaryFormat::Elf => {
             let section = link_section.unwrap_or(format!(".text.{asm_name}"));