check link ordinal make sure target is foreign function

Author: chenyukang

compiler/rustc_error_messages/locales/en-US/passes.ftl

@@ -262,3 +262,6 @@ passes-rustc-lint-opt-ty = `#[rustc_lint_opt_ty]` should be applied to a struct
 
 passes-rustc-lint-opt-deny-field-access = `#[rustc_lint_opt_deny_field_access]` should be applied to a field
     .label = not a field
+
+passes-link-ordinal = attribute should be applied to a foreign function
+    .label = not a foreign function

compiler/rustc_passes/src/check_attr.rs

@@ -146,6 +146,9 @@ impl CheckAttrVisitor<'_> {
                 | sym::stable
                 | sym::rustc_allowed_through_unstable_modules
                 | sym::rustc_promotable => self.check_stability_promotable(&attr, span, target),
+                sym::link_ordinal => {
+                    self.check_link_ordinal(&attr, span, target)
+                },
                 _ => true,
             };
             is_valid &= attr_is_valid;
@@ -1861,6 +1864,16 @@ impl CheckAttrVisitor<'_> {
         }
     }
 
+    fn check_link_ordinal(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
+        match target {
+            Target::ForeignFn => true,
+            _ => {
+                self.tcx.sess.emit_err(errors::LinkOrdinal { attr_span: attr.span });
+                false
+            }
+        }
+    }
+
     fn check_deprecated(&self, hir_id: HirId, attr: &Attribute, _span: Span, target: Target) {
         match target {
             Target::Closure | Target::Expression | Target::Statement | Target::Arm => {

compiler/rustc_passes/src/errors.rs

@@ -551,6 +551,13 @@ pub struct ConstTrait {
     pub attr_span: Span,
 }
 
+#[derive(SessionDiagnostic)]
+#[error(passes::link_ordinal)]
+pub struct LinkOrdinal {
+    #[primary_span]
+    pub attr_span: Span
+}
+
 #[derive(SessionDiagnostic)]
 #[error(passes::stability_promotable)]
 pub struct StabilityPromotable {

src/test/ui/rfc-2627-raw-dylib/link-ordinal-not-foreign-fn.rs

@@ -0,0 +1,18 @@
+#![feature(raw_dylib)]
+//~^ WARN the feature `raw_dylib` is incomplete
+
+#[link_ordinal(123)]
+//~^ ERROR attribute should be applied to a foreign function
+struct Foo {}
+
+#[link_ordinal(123)]
+//~^ ERROR attribute should be applied to a foreign function
+fn test() {}
+
+#[link(name = "exporter", kind = "raw-dylib")]
+extern {
+    #[link_ordinal(13)]
+    fn imported_function();
+}
+
+fn main() {}

src/test/ui/rfc-2627-raw-dylib/link-ordinal-not-foreign-fn.stderr

@@ -0,0 +1,23 @@
+warning: the feature `raw_dylib` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/link-ordinal-not-foreign-fn.rs:1:12
+   |
+LL | #![feature(raw_dylib)]
+   |            ^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #58713 <https://github.com/rust-lang/rust/issues/58713> for more information
+
+error: attribute should be applied to a foreign function
+  --> $DIR/link-ordinal-not-foreign-fn.rs:4:1
+   |
+LL | #[link_ordinal(123)]
+   | ^^^^^^^^^^^^^^^^^^^^
+
+error: attribute should be applied to a foreign function
+  --> $DIR/link-ordinal-not-foreign-fn.rs:8:1
+   |
+LL | #[link_ordinal(123)]
+   | ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors; 1 warning emitted
+