work on darwin_objc PR feedback

Author: jbatez

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -164,9 +164,9 @@ pub(crate) struct ObjcClassParser;
 impl<S: Stage> SingleAttributeParser<S> for ObjcClassParser {
     const PATH: &[rustc_span::Symbol] = &[sym::rustc_objc_class];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepInnermost;
-    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowListWarnRest(&[Allow(Target::ForeignStatic)]);
+        AllowedTargets::AllowList(&[Allow(Target::ForeignStatic)]);
     const TEMPLATE: AttributeTemplate = template!(NameValueStr: "ClassName");
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
@@ -193,9 +193,9 @@ pub(crate) struct ObjcSelectorParser;
 impl<S: Stage> SingleAttributeParser<S> for ObjcSelectorParser {
     const PATH: &[rustc_span::Symbol] = &[sym::rustc_objc_selector];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepInnermost;
-    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowListWarnRest(&[Allow(Target::ForeignStatic)]);
+        AllowedTargets::AllowList(&[Allow(Target::ForeignStatic)]);
     const TEMPLATE: AttributeTemplate = template!(NameValueStr: "methodName");
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {

compiler/rustc_codegen_llvm/src/base.rs

@@ -111,6 +111,10 @@ pub(crate) fn compile_codegen_unit(
 
             // Define Objective-C module info for 32-bit x86 macOS. Note, this generates a global
             // that gets added to the `llvm.compiler.used` variable, created later.
+            //
+            // This is only necessary when we need the linker to do its Objective-C-specific magic.
+            // We could theoretically do it unconditionally, but at a slight cost to linker
+            // performance in the common case where it's unnecessary.
             let uses_objc =
                 !cx.objc_classrefs.borrow().is_empty() || !cx.objc_selrefs.borrow().is_empty();
             if uses_objc && cx.tcx.sess.target.arch == "x86" && cx.tcx.sess.target.os == "macos" {
@@ -141,6 +145,10 @@ pub(crate) fn compile_codegen_unit(
             }
 
             // Add Objective-C module flags.
+            //
+            // This is only necessary when we need the linker to do its Objective-C-specific magic.
+            // We could theoretically do it unconditionally, but at a slight cost to linker
+            // performance in the common case where it's unnecessary.
             if uses_objc {
                 cx.add_objc_module_flags();
             }

compiler/rustc_codegen_llvm/src/consts.rs

@@ -588,6 +588,10 @@ impl<'ll> CodegenCx<'ll, '_> {
         class_t
     }
 
+    // We do our best here to match what Clang does when compiling Objective-C natively. We
+    // deduplicate references within a CGU, but we need a reference definition in each referencing
+    // CGU. All attempts at using external references to a single reference definition result in
+    // linker errors.
     fn get_objc_classref(&self, classname: Symbol) -> &'ll Value {
         let mut classrefs = self.objc_classrefs.borrow_mut();
         if let Some(classref) = classrefs.get(&classname).copied() {
@@ -631,6 +635,10 @@ impl<'ll> CodegenCx<'ll, '_> {
         g
     }
 
+    // We do our best here to match what Clang does when compiling Objective-C natively. We
+    // deduplicate references within a CGU, but we need a reference definition in each referencing
+    // CGU. All attempts at using external references to a single reference definition result in
+    // linker errors.
     fn get_objc_selref(&self, methname: Symbol) -> &'ll Value {
         let mut selrefs = self.objc_selrefs.borrow_mut();
         if let Some(selref) = selrefs.get(&methname).copied() {
@@ -684,6 +692,13 @@ impl<'ll> CodegenCx<'ll, '_> {
         assert_eq!(self.tcx.sess.target.arch, "x86");
         assert_eq!(self.tcx.sess.target.os, "macos");
 
+        // struct _objc_module {
+        //     long version;                // Hardcoded to 7 in Clang.
+        //     long size;                   // sizeof(struct _objc_module)
+        //     char *name;                  // Hardcoded to classname "" in Clang.
+        //     struct _objc_symtab* symtab; // Null without class or category definitions.
+        //  }
+
         let llty = self.type_named_struct("struct._objc_module");
         let i32_llty = self.type_i32();
         let ptr_llty = self.type_ptr();

compiler/rustc_codegen_llvm/src/context.rs

@@ -709,7 +709,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             },
         );
 
-        if self.tcx.sess.target.abi == "sim" {
+        if self.tcx.sess.target.env == "sim" {
             llvm::add_module_flag_u32(
                 self.llmod,
                 llvm::ModuleFlagMergeBehavior::Error,

compiler/rustc_feature/src/builtin_attrs.rs

@@ -1049,11 +1049,11 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         EncodeCrossCrate::No,
     ),
     rustc_attr!(
-        rustc_objc_class, Normal, template!(NameValueStr: "ClassName"), FutureWarnPreceding,
+        rustc_objc_class, Normal, template!(NameValueStr: "ClassName"), ErrorPreceding,
         EncodeCrossCrate::Yes,
     ),
     rustc_attr!(
-        rustc_objc_selector, Normal, template!(NameValueStr: "methodName"), FutureWarnPreceding,
+        rustc_objc_selector, Normal, template!(NameValueStr: "methodName"), ErrorPreceding,
         EncodeCrossCrate::Yes,
     ),
 

library/core/src/os/darwin/objc.rs

@@ -1,6 +1,7 @@
 //! Defines types and macros for Objective-C interoperability.
 
 #![unstable(feature = "darwin_objc", issue = "145496")]
+#![allow(nonstandard_style)]
 
 use crate::fmt;
 

library/core/src/os/mod.rs

@@ -1,7 +1,6 @@
 //! OS-specific functionality.
 
 #![unstable(feature = "darwin_objc", issue = "145496")]
-#![allow(nonstandard_style)]
 
 // darwin
 #[cfg(not(all(