Add raw_dylib_macho feature gate

Author: madsmtm

compiler/rustc_attr_parsing/messages.ftl

@@ -242,6 +242,12 @@ attr_parsing_raw_dylib_no_nul =
 attr_parsing_raw_dylib_elf_unstable =
     link kind `raw-dylib` is unstable on ELF platforms
 
+attr_parsing_raw_dylib_macho_unstable =
+    link kind `raw-dylib` is unstable on Mach-O platforms
+
+attr_parsing_raw_dylib_macho_use_verbatim =
+    link kind `raw-dylib` should use the `+verbatim` linkage modifier
+
 attr_parsing_raw_dylib_only_windows =
     link kind `raw-dylib` is only supported on Windows targets
 

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -13,8 +13,8 @@ use crate::fluent_generated;
 use crate::session_diagnostics::{
     AsNeededCompatibility, BundleNeedsStatic, EmptyLinkName, ImportNameTypeRaw, ImportNameTypeX86,
     IncompatibleWasmLink, InvalidLinkModifier, LinkFrameworkApple, LinkOrdinalOutOfRange,
-    LinkRequiresName, MultipleModifiers, NullOnLinkSection, RawDylibNoNul, RawDylibOnlyWindows,
-    WholeArchiveNeedsStatic,
+    LinkRequiresName, MultipleModifiers, NullOnLinkSection, RawDylibMachoUseVerbatim,
+    RawDylibNoNul, RawDylibOnlyWindows, WholeArchiveNeedsStatic,
 };
 
 pub(crate) struct LinkNameParser;
@@ -218,6 +218,17 @@ impl<S: Stage> CombineAttributeParser<S> for LinkParser {
             cx.emit_err(RawDylibNoNul { span: name_span });
         }
 
+        if sess.target.binary_format == BinaryFormat::MachO
+            && kind == Some(NativeLibKind::RawDylib)
+            && verbatim != Some(true)
+        {
+            // It is possible for us to emit a non-absolute path like `libSystem.dylib` in the
+            // binary and have that work as well, though it's unclear what the use-case of that
+            // would be, and it might lead to people accidentally specifying too "lax" linking.
+            // So let's disallow it for now.
+            cx.emit_err(RawDylibMachoUseVerbatim { span: cx.attr_span });
+        }
+
         result = Some(LinkEntry {
             span: cx.attr_span,
             kind: kind.unwrap_or(NativeLibKind::Unspecified),
@@ -286,22 +297,42 @@ impl LinkParser {
                 NativeLibKind::Framework { as_needed: None }
             }
             sym::raw_dash_dylib => {
-                if sess.target.is_like_windows {
-                    // raw-dylib is stable and working on Windows
-                } else if sess.target.binary_format == BinaryFormat::Elf && features.raw_dylib_elf()
-                {
-                    // raw-dylib is unstable on ELF, but the user opted in
-                } else if sess.target.binary_format == BinaryFormat::Elf && sess.is_nightly_build()
-                {
-                    feature_err(
-                        sess,
-                        sym::raw_dylib_elf,
-                        nv.value_span,
-                        fluent_generated::attr_parsing_raw_dylib_elf_unstable,
-                    )
-                    .emit();
-                } else {
-                    cx.emit_err(RawDylibOnlyWindows { span: nv.value_span });
+                match sess.target.binary_format {
+                    _ if sess.target.is_like_windows => {
+                        // raw-dylib is stable and working on Windows
+                    }
+
+                    BinaryFormat::Elf if features.raw_dylib_elf() => {
+                        // raw-dylib is unstable on ELF, but the user opted in
+                    }
+                    BinaryFormat::Elf if sess.is_nightly_build() => {
+                        // Incomplete, so don't recommend if not nightly.
+                        feature_err(
+                            sess,
+                            sym::raw_dylib_elf,
+                            nv.value_span,
+                            fluent_generated::attr_parsing_raw_dylib_elf_unstable,
+                        )
+                        .emit();
+                    }
+
+                    BinaryFormat::MachO if features.raw_dylib_macho() => {
+                        // raw-dylib is unstable on Mach-O, but the user opted in
+                    }
+                    BinaryFormat::MachO if sess.is_nightly_build() => {
+                        // Incomplete, so don't recommend if not nightly.
+                        feature_err(
+                            sess,
+                            sym::raw_dylib_macho,
+                            nv.value_span,
+                            fluent_generated::attr_parsing_raw_dylib_macho_unstable,
+                        )
+                        .emit();
+                    }
+
+                    _ => {
+                        cx.emit_err(RawDylibOnlyWindows { span: nv.value_span });
+                    }
                 }
 
                 NativeLibKind::RawDylib

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -881,6 +881,13 @@ pub(crate) struct RawDylibOnlyWindows {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(attr_parsing_raw_dylib_macho_use_verbatim)]
+pub(crate) struct RawDylibMachoUseVerbatim {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(attr_parsing_invalid_link_modifier)]
 pub(crate) struct InvalidLinkModifier {

compiler/rustc_feature/src/unstable.rs

@@ -611,8 +611,10 @@ declare_features! (
     (unstable, postfix_match, "1.79.0", Some(121618)),
     /// Allows macro attributes on expressions, statements and non-inline modules.
     (unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
-    /// Allows the use of raw-dylibs on ELF platforms
+    /// Allows the use of raw-dylibs on ELF platforms.
     (incomplete, raw_dylib_elf, "1.87.0", Some(135694)),
+    /// Allows the use of raw-dylibs on Mach-O platforms.
+    (incomplete, raw_dylib_macho, "CURRENT_RUSTC_VERSION", Some(146356)),
     (unstable, reborrow, "CURRENT_RUSTC_VERSION", Some(145612)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
     (incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),

compiler/rustc_span/src/symbol.rs

@@ -1751,6 +1751,7 @@ symbols! {
         raw_dash_dylib: "raw-dylib",
         raw_dylib,
         raw_dylib_elf,
+        raw_dylib_macho,
         raw_eq,
         raw_identifiers,
         raw_ref_op,

tests/ui/feature-gates/feature-gate-raw-dylib-macho.rs

@@ -0,0 +1,10 @@
+//@ only-apple
+//@ needs-dynamic-linking
+
+#[link(name = "uwu", kind = "raw-dylib", modifiers = "+verbatim")]
+//~^ ERROR: link kind `raw-dylib` is unstable on Mach-O platforms
+unsafe extern "C" {
+    safe fn kawaii();
+}
+
+fn main() {}

tests/ui/feature-gates/feature-gate-raw-dylib-macho.stderr

@@ -0,0 +1,12 @@
+error[E0658]: link kind `raw-dylib` is unstable on Mach-O platforms
+  --> $DIR/feature-gate-raw-dylib-macho.rs:4:29
+   |
+LL | #[link(name = "uwu", kind = "raw-dylib", modifiers = "+verbatim")]
+   |                             ^^^^^^^^^^^
+   |
+   = help: add `#![feature(raw_dylib_macho)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.

tests/ui/linkage-attr/raw-dylib/macho/empty.rs

@@ -0,0 +1,10 @@
+//@ only-apple
+//@ build-pass
+
+#![allow(incomplete_features)]
+#![feature(raw_dylib_macho)]
+
+#[link(name = "hack", kind = "raw-dylib", modifiers = "+verbatim")]
+unsafe extern "C" {}
+
+fn main() {}

tests/ui/linkage-attr/raw-dylib/windows/raw-dylib-windows-only.rs

@@ -1,9 +1,13 @@
-//@ revisions: elf notelf
+//@ revisions: elf notelf macho
 //@ [elf] only-elf
+//@ [macho] only-apple
 //@ [notelf] ignore-windows
 //@ [notelf] ignore-elf
+//@ [notelf] ignore-apple
 //@ compile-flags: --crate-type lib
 #[link(name = "foo", kind = "raw-dylib")]
 //[notelf]~^ ERROR: link kind `raw-dylib` is only supported on Windows targets
 //[elf]~^^ ERROR: link kind `raw-dylib` is unstable on ELF platforms
+//[macho]~^^^ ERROR: link kind `raw-dylib` is unstable on Mach-O platforms
+//[macho]~^^^^ ERROR: link kind `raw-dylib` should use the `+verbatim` linkage modifier
 extern "C" {}