Port #[link_section] to the new attribute parsing infrastructure

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -256,6 +256,9 @@ pub enum AttributeKind {
     /// Represents `#[link_name]`.
     LinkName { name: Symbol, span: Span },
 
+    /// Represents [`#[link_section]`](https://doc.rust-lang.org/reference/abi.html#the-link_section-attribute)
+    LinkSection { name: Symbol, span: Span },
+
     /// Represents `#[loop_match]`.
     LoopMatch(Span),
 

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -24,6 +24,7 @@ impl AttributeKind {
             DocComment { .. } => Yes,
             ExportName { .. } => Yes,
             Inline(..) => No,
+            LinkSection { .. } => No,
             MacroTransparency(..) => Yes,
             Repr(..) => No,
             Stability { .. } => Yes,

compiler/rustc_attr_parsing/messages.ftl

@@ -99,6 +99,8 @@ attr_parsing_non_ident_feature =
 
 attr_parsing_null_on_export = `export_name` may not contain null characters
 
+attr_parsing_null_on_link_section = `link_section` may not contain null characters
+
 attr_parsing_repr_ident =
     meta item in `repr` must be an identifier
 

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -1,11 +1,12 @@
 use rustc_attr_data_structures::AttributeKind;
-use rustc_attr_data_structures::AttributeKind::LinkName;
+use rustc_attr_data_structures::AttributeKind::{LinkName, LinkSection};
 use rustc_feature::{AttributeTemplate, template};
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
 use crate::context::{AcceptContext, Stage};
 use crate::parser::ArgParser;
+use crate::session_diagnostics::NullOnLinkSection;
 
 pub(crate) struct LinkNameParser;
 
@@ -28,3 +29,31 @@ impl<S: Stage> SingleAttributeParser<S> for LinkNameParser {
         Some(LinkName { name, span: cx.attr_span })
     }
 }
+
+pub(crate) struct LinkSectionParser;
+
+impl<S: Stage> SingleAttributeParser<S> for LinkSectionParser {
+    const PATH: &[Symbol] = &[sym::link_section];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "name");
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let Some(nv) = args.name_value() else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+        let Some(name) = nv.value_as_str() else {
+            cx.expected_string_literal(nv.value_span, Some(nv.value_as_lit()));
+            return None;
+        };
+        if name.as_str().contains('\0') {
+            // `#[link_section = ...]` will be converted to a null-terminated string,
+            // so it may not contain any null characters.
+            cx.emit_err(NullOnLinkSection { span: cx.attr_span });
+            return None;
+        }
+
+        Some(LinkSection { name, span: cx.attr_span })
+    }
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -22,7 +22,7 @@ use crate::attributes::codegen_attrs::{
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
-use crate::attributes::link_attrs::LinkNameParser;
+use crate::attributes::link_attrs::{LinkNameParser, LinkSectionParser};
 use crate::attributes::lint_helpers::{AsPtrParser, PubTransparentParser};
 use crate::attributes::loop_match::{ConstContinueParser, LoopMatchParser};
 use crate::attributes::must_use::MustUseParser;
@@ -123,6 +123,7 @@ attribute_parsers!(
         Single<ExportNameParser>,
         Single<InlineParser>,
         Single<LinkNameParser>,
+        Single<LinkSectionParser>,
         Single<LoopMatchParser>,
         Single<MayDangleParser>,
         Single<MustUseParser>,

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -452,6 +452,13 @@ pub(crate) struct NullOnExport {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(attr_parsing_null_on_link_section, code = E0648)]
+pub(crate) struct NullOnLinkSection {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(attr_parsing_stability_outside_std, code = E0734)]
 pub(crate) struct StabilityOutsideStd {

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -124,6 +124,9 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                 AttributeKind::Naked(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED,
                 AttributeKind::Align { align, .. } => codegen_fn_attrs.alignment = Some(*align),
                 AttributeKind::LinkName { name, .. } => codegen_fn_attrs.link_name = Some(*name),
+                AttributeKind::LinkSection { name, .. } => {
+                    codegen_fn_attrs.link_section = Some(*name)
+                }
                 AttributeKind::NoMangle(attr_span) => {
                     if tcx.opt_item_name(did.to_def_id()).is_some() {
                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
@@ -253,16 +256,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     }
                 }
             }
-            sym::link_section => {
-                if let Some(val) = attr.value_str() {
-                    if val.as_str().bytes().any(|b| b == 0) {
-                        let msg = format!("illegal null byte in link_section value: `{val}`");
-                        tcx.dcx().span_err(attr.span(), msg);
-                    } else {
-                        codegen_fn_attrs.link_section = Some(val);
-                    }
-                }
-            }
             sym::link_ordinal => {
                 link_ordinal_span = Some(attr.span());
                 if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {

compiler/rustc_passes/src/check_attr.rs

@@ -177,6 +177,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::Align { align, span: repr_span }) => {
                     self.check_align(span, target, *align, *repr_span)
                 }
+                Attribute::Parsed(AttributeKind::LinkSection { span: attr_span, .. }) => {
+                    self.check_link_section(hir_id, *attr_span, span, target)
+                }
                 Attribute::Parsed(AttributeKind::Naked(attr_span)) => {
                     self.check_naked(hir_id, *attr_span, span, target)
                 }
@@ -286,7 +289,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::ffi_const, ..] => self.check_ffi_const(attr.span(), target),
                         [sym::link_ordinal, ..] => self.check_link_ordinal(attr, span, target),
                         [sym::link, ..] => self.check_link(hir_id, attr, span, target),
-                        [sym::link_section, ..] => self.check_link_section(hir_id, attr, span, target),
                         [sym::macro_use, ..] | [sym::macro_escape, ..] => {
                             self.check_macro_use(hir_id, attr, target)
                         }
@@ -1831,23 +1833,23 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     /// Checks if `#[link_section]` is applied to a function or static.
-    fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
+    fn check_link_section(&self, hir_id: HirId, attr_span: Span, span: Span, target: Target) {
         match target {
             Target::Static | Target::Fn | Target::Method(..) => {}
             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
             // `#[link_section]` attribute with just a lint, because we previously
             // erroneously allowed it and some crates used it accidentally, to be compatible
             // with crates depending on them, we can't throw an error here.
             Target::Field | Target::Arm | Target::MacroDef => {
-                self.inline_attr_str_error_with_macro_def(hir_id, attr.span(), "link_section");
+                self.inline_attr_str_error_with_macro_def(hir_id, attr_span, "link_section");
             }
             _ => {
                 // FIXME: #[link_section] was previously allowed on non-functions/statics and some
                 // crates used this, so only emit a warning.
                 self.tcx.emit_node_span_lint(
                     UNUSED_ATTRIBUTES,
                     hir_id,
-                    attr.span(),
+                    attr_span,
                     errors::LinkSection { span },
                 );
             }

src/librustdoc/clean/types.rs

@@ -753,9 +753,12 @@ impl Item {
             .other_attrs
             .iter()
             .filter_map(|attr| {
+                if let hir::Attribute::Parsed(AttributeKind::LinkSection { name, .. }) = attr {
+                    Some(format!("#[link_section = \"{name}\"]"))
+                }
                 // NoMangle is special cased, as it appears in HTML output, and we want to show it in source form, not HIR printing.
                 // It is also used by cargo-semver-checks.
-                if let hir::Attribute::Parsed(AttributeKind::NoMangle(..)) = attr {
+                else if let hir::Attribute::Parsed(AttributeKind::NoMangle(..)) = attr {
                     Some("#[no_mangle]".to_string())
                 } else if let hir::Attribute::Parsed(AttributeKind::ExportName { name, .. }) = attr
                 {

tests/rustdoc-json/attrs/link_section_2021.rs

@@ -0,0 +1,6 @@
+//@ edition: 2021
+#![no_std]
+
+//@ is "$.index[?(@.name=='example')].attrs" '["#[link_section = \".text\"]"]'
+#[link_section = ".text"]
+pub extern "C" fn example() {}

tests/rustdoc-json/attrs/link_section_2024.rs

@@ -0,0 +1,9 @@
+//@ edition: 2024
+#![no_std]
+
+// Since the 2024 edition the link_section attribute must use the unsafe qualification.
+// However, the unsafe qualification is not shown by rustdoc.
+
+//@ is "$.index[?(@.name=='example')].attrs" '["#[link_section = \".text\"]"]'
+#[unsafe(link_section = ".text")]
+pub extern "C" fn example() {}

tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.stderr

@@ -387,14 +387,6 @@ LL | #![link()]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
-warning: attribute should be applied to a function or static
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:69:1
-   |
-LL | #![link_section = "1800"]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ not a function or static
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-
 warning: attribute should be applied to a function definition
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:62:1
    |
@@ -411,6 +403,14 @@ LL | #![link_name = "1900"]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 
+warning: attribute should be applied to a function or static
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:69:1
+   |
+LL | #![link_section = "1800"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ not a function or static
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+
 warning: `#[must_use]` has no effect when applied to a module
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:72:1
    |

tests/ui/lint/unused/unused-attr-duplicate.rs

@@ -102,4 +102,10 @@ pub fn no_mangle_test() {}
 #[used] //~ ERROR unused attribute
 static FOO: u32 = 0;
 
+#[link_section = ".text"]
+//~^ ERROR unused attribute
+//~| WARN this was previously accepted
+#[link_section = ".bss"]
+pub extern "C" fn example() {}
+
 fn main() {}

tests/ui/lint/unused/unused-attr-duplicate.stderr

@@ -289,5 +289,18 @@ note: attribute also specified here
 LL | #[used]
    | ^^^^^^^
 
-error: aborting due to 23 previous errors
+error: unused attribute
+  --> $DIR/unused-attr-duplicate.rs:105:1
+   |
+LL | #[link_section = ".text"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove this attribute
+   |
+note: attribute also specified here
+  --> $DIR/unused-attr-duplicate.rs:108:1
+   |
+LL | #[link_section = ".bss"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+
+error: aborting due to 24 previous errors