Rollup of 8 pull requests

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -130,24 +130,54 @@ impl Deprecation {
     }
 }
 
-/// Represent parsed, *built in*, inert attributes.
+/// Represents parsed *built-in* inert attributes.
 ///
-/// That means attributes that are not actually ever expanded.
-/// For more information on this, see the module docs on the [`rustc_attr_parsing`] crate.
-/// They're instead used as markers, to guide the compilation process in various way in most every stage of the compiler.
-/// These are kept around after the AST, into the HIR and further on.
+/// ## Overview
+/// These attributes are markers that guide the compilation process and are never expanded into other code.
+/// They persist throughout the compilation phases, from AST to HIR and beyond.
 ///
-/// The word "parsed" could be a little misleading here, because the parser already parses
-/// attributes early on. However, the result, an [`ast::Attribute`]
-/// is only parsed at a high level, still containing a token stream in many cases. That is
-/// because the structure of the contents varies from attribute to attribute.
-/// With a parsed attribute I mean that each attribute is processed individually into a
-/// final structure, which on-site (the place where the attribute is useful for, think the
-/// the place where `must_use` is checked) little to no extra parsing or validating needs to
-/// happen.
+/// ## Attribute Processing
+/// While attributes are initially parsed by [`rustc_parse`] into [`ast::Attribute`], they still contain raw token streams
+/// because different attributes have different internal structures. This enum represents the final,
+/// fully parsed form of these attributes, where each variant contains contains all the information and
+/// structure relevant for the specific attribute.
 ///
-/// For more docs, look in [`rustc_attr_parsing`].
+/// Some attributes can be applied multiple times to the same item, and they are "collapsed" into a single
+/// semantic attribute. For example:
+/// ```rust
+/// #[repr(C)]
+/// #[repr(packed)]
+/// struct S { }
+/// ```
+/// This is equivalent to `#[repr(C, packed)]` and results in a single [`AttributeKind::Repr`] containing
+/// both `C` and `packed` annotations. This collapsing happens during parsing and is reflected in the
+/// data structures defined in this enum.
 ///
+/// ## Usage
+/// These parsed attributes are used throughout the compiler to:
+/// - Control code generation (e.g., `#[repr]`)
+/// - Mark API stability (`#[stable]`, `#[unstable]`)
+/// - Provide documentation (`#[doc]`)
+/// - Guide compiler behavior (e.g., `#[allow_internal_unstable]`)
+///
+/// ## Note on Attribute Organization
+/// Some attributes like `InlineAttr`, `OptimizeAttr`, and `InstructionSetAttr` are defined separately
+/// from this enum because they are used in specific compiler phases (like code generation) and don't
+/// need to persist throughout the entire compilation process. They are typically processed and
+/// converted into their final form earlier in the compilation pipeline.
+///
+/// For example:
+/// - `InlineAttr` is used during code generation to control function inlining
+/// - `OptimizeAttr` is used to control optimization levels
+/// - `InstructionSetAttr` is used for target-specific code generation
+///
+/// These attributes are handled by their respective compiler passes in the [`rustc_codegen_ssa`] crate
+/// and don't need to be preserved in the same way as the attributes in this enum.
+///
+/// For more details on attribute parsing, see the [`rustc_attr_parsing`] crate.
+///
+/// [`rustc_parse`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_parse/index.html
+/// [`rustc_codegen_ssa`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_codegen_ssa/index.html
 /// [`rustc_attr_parsing`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html
 #[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable, PrintAttribute)]
 pub enum AttributeKind {

compiler/rustc_attr_data_structures/src/lib.rs

@@ -1,3 +1,7 @@
+//! Data structures for representing parsed attributes in the Rust compiler.
+//! For detailed documentation about attribute processing,
+//! see [rustc_attr_parsing](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html).
+
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![doc(rust_logo)]

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -1829,6 +1829,7 @@ pub(crate) fn linked_symbols(
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
         if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum)
             || info.used
+            || info.rustc_std_internal_symbol
         {
             symbols.push((
                 symbol_export::linking_symbol_name_for_instance_in_crate(tcx, symbol, cnum),

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -131,6 +131,9 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap<S
                 used: codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER)
                     || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
                     || used,
+                rustc_std_internal_symbol: codegen_attrs
+                    .flags
+                    .contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL),
             };
             (def_id.to_def_id(), info)
         })
@@ -143,6 +146,7 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap<S
                 level: SymbolExportLevel::C,
                 kind: SymbolExportKind::Data,
                 used: false,
+                rustc_std_internal_symbol: false,
             },
         );
     }
@@ -191,6 +195,7 @@ fn exported_symbols_provider_local<'tcx>(
                         level: info.level,
                         kind: SymbolExportKind::Text,
                         used: info.used,
+                        rustc_std_internal_symbol: info.rustc_std_internal_symbol,
                     },
                 )
             })
@@ -207,6 +212,7 @@ fn exported_symbols_provider_local<'tcx>(
                 level: SymbolExportLevel::C,
                 kind: SymbolExportKind::Text,
                 used: false,
+                rustc_std_internal_symbol: false,
             },
         ));
     }
@@ -229,6 +235,7 @@ fn exported_symbols_provider_local<'tcx>(
                     level: SymbolExportLevel::Rust,
                     kind: SymbolExportKind::Text,
                     used: false,
+                    rustc_std_internal_symbol: true,
                 },
             ));
         }
@@ -243,6 +250,7 @@ fn exported_symbols_provider_local<'tcx>(
                 level: SymbolExportLevel::Rust,
                 kind: SymbolExportKind::Data,
                 used: false,
+                rustc_std_internal_symbol: true,
             },
         ))
     }
@@ -262,6 +270,7 @@ fn exported_symbols_provider_local<'tcx>(
                     level: SymbolExportLevel::C,
                     kind: SymbolExportKind::Data,
                     used: false,
+                    rustc_std_internal_symbol: false,
                 },
             )
         }));
@@ -287,6 +296,7 @@ fn exported_symbols_provider_local<'tcx>(
                     level: SymbolExportLevel::C,
                     kind: SymbolExportKind::Data,
                     used: false,
+                    rustc_std_internal_symbol: false,
                 },
             )
         }));
@@ -304,6 +314,7 @@ fn exported_symbols_provider_local<'tcx>(
                 level: SymbolExportLevel::C,
                 kind: SymbolExportKind::Data,
                 used: true,
+                rustc_std_internal_symbol: false,
             },
         ));
     }
@@ -379,6 +390,8 @@ fn exported_symbols_provider_local<'tcx>(
                 }
             }
 
+            // Note: These all set rustc_std_internal_symbol to false as generic functions must not
+            // be marked with this attribute and we are only handling generic functions here.
             match *mono_item {
                 MonoItem::Fn(Instance { def: InstanceKind::Item(def), args }) => {
                     let has_generics = args.non_erasable_generics().next().is_some();
@@ -394,6 +407,7 @@ fn exported_symbols_provider_local<'tcx>(
                                 level: SymbolExportLevel::Rust,
                                 kind: SymbolExportKind::Text,
                                 used: false,
+                                rustc_std_internal_symbol: false,
                             },
                         ));
                     }
@@ -416,6 +430,7 @@ fn exported_symbols_provider_local<'tcx>(
                                 level: SymbolExportLevel::Rust,
                                 kind: SymbolExportKind::Text,
                                 used: false,
+                                rustc_std_internal_symbol: false,
                             },
                         ));
                     }
@@ -432,6 +447,7 @@ fn exported_symbols_provider_local<'tcx>(
                             level: SymbolExportLevel::Rust,
                             kind: SymbolExportKind::Text,
                             used: false,
+                            rustc_std_internal_symbol: false,
                         },
                     ));
                 }
@@ -442,6 +458,7 @@ fn exported_symbols_provider_local<'tcx>(
                             level: SymbolExportLevel::Rust,
                             kind: SymbolExportKind::Text,
                             used: false,
+                            rustc_std_internal_symbol: false,
                         },
                     ));
                 }

compiler/rustc_codegen_ssa/src/base.rs

@@ -6,7 +6,7 @@ use std::time::{Duration, Instant};
 use itertools::Itertools;
 use rustc_abi::FIRST_VARIANT;
 use rustc_ast as ast;
-use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_name};
+use rustc_ast::expand::allocator::AllocatorKind;
 use rustc_attr_data_structures::OptimizeAttr;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
@@ -1039,26 +1039,6 @@ impl CrateInfo {
                         .collect::<Vec<_>>();
                     symbols.sort_unstable_by(|a, b| a.0.cmp(&b.0));
                     linked_symbols.extend(symbols);
-                    if tcx.allocator_kind(()).is_some() {
-                        // At least one crate needs a global allocator. This crate may be placed
-                        // after the crate that defines it in the linker order, in which case some
-                        // linkers return an error. By adding the global allocator shim methods to
-                        // the linked_symbols list, linking the generated symbols.o will ensure that
-                        // circular dependencies involving the global allocator don't lead to linker
-                        // errors.
-                        linked_symbols.extend(ALLOCATOR_METHODS.iter().map(|method| {
-                            (
-                                format!(
-                                    "{prefix}{}",
-                                    mangle_internal_symbol(
-                                        tcx,
-                                        global_fn_name(method.name).as_str()
-                                    )
-                                ),
-                                SymbolExportKind::Text,
-                            )
-                        }));
-                    }
                 });
         }
 

compiler/rustc_feature/src/builtin_attrs.rs

@@ -887,7 +887,7 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         rustc_legacy_const_generics, Normal, template!(List: "N"), ErrorFollowing,
         EncodeCrossCrate::Yes,
     ),
-    // Do not const-check this function's body. It will always get replaced during CTFE.
+    // Do not const-check this function's body. It will always get replaced during CTFE via `hook_special_const_fn`.
     rustc_attr!(
         rustc_do_not_const_check, Normal, template!(Word), WarnFollowing,
         EncodeCrossCrate::Yes, "`#[rustc_do_not_const_check]` skips const-check for this function's body",

compiler/rustc_metadata/src/creader.rs

@@ -1,7 +1,6 @@
 //! Validates all used crates and extern libraries and loads their metadata
 
 use std::error::Error;
-use std::ops::Fn;
 use std::path::Path;
 use std::str::FromStr;
 use std::time::Duration;
@@ -276,12 +275,6 @@ impl CStore {
             .filter_map(|(cnum, data)| data.as_deref().map(|data| (cnum, data)))
     }
 
-    fn iter_crate_data_mut(&mut self) -> impl Iterator<Item = (CrateNum, &mut CrateMetadata)> {
-        self.metas
-            .iter_enumerated_mut()
-            .filter_map(|(cnum, data)| data.as_deref_mut().map(|data| (cnum, data)))
-    }
-
     fn push_dependencies_in_postorder(&self, deps: &mut IndexSet<CrateNum>, cnum: CrateNum) {
         if !deps.contains(&cnum) {
             let data = self.get_crate_data(cnum);
@@ -307,13 +300,6 @@ impl CStore {
         deps
     }
 
-    fn crate_dependencies_in_reverse_postorder(
-        &self,
-        cnum: CrateNum,
-    ) -> impl Iterator<Item = CrateNum> {
-        self.crate_dependencies_in_postorder(cnum).into_iter().rev()
-    }
-
     pub(crate) fn injected_panic_runtime(&self) -> Option<CrateNum> {
         self.injected_panic_runtime
     }
@@ -966,47 +952,27 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         // If we need a panic runtime, we try to find an existing one here. At
         // the same time we perform some general validation of the DAG we've got
         // going such as ensuring everything has a compatible panic strategy.
-        //
-        // The logic for finding the panic runtime here is pretty much the same
-        // as the allocator case with the only addition that the panic strategy
-        // compilation mode also comes into play.
-        let desired_strategy = self.sess.panic_strategy();
-        let mut runtime_found = false;
         let mut needs_panic_runtime = attr::contains_name(&krate.attrs, sym::needs_panic_runtime);
-
-        let mut panic_runtimes = Vec::new();
-        for (cnum, data) in self.cstore.iter_crate_data() {
-            needs_panic_runtime = needs_panic_runtime || data.needs_panic_runtime();
-            if data.is_panic_runtime() {
-                // Inject a dependency from all #![needs_panic_runtime] to this
-                // #![panic_runtime] crate.
-                panic_runtimes.push(cnum);
-                runtime_found = runtime_found || data.dep_kind() == CrateDepKind::Explicit;
-            }
-        }
-        for cnum in panic_runtimes {
-            self.inject_dependency_if(cnum, "a panic runtime", &|data| data.needs_panic_runtime());
+        for (_cnum, data) in self.cstore.iter_crate_data() {
+            needs_panic_runtime |= data.needs_panic_runtime();
         }
 
-        // If an explicitly linked and matching panic runtime was found, or if
-        // we just don't need one at all, then we're done here and there's
-        // nothing else to do.
-        if !needs_panic_runtime || runtime_found {
+        // If we just don't need a panic runtime at all, then we're done here
+        // and there's nothing else to do.
+        if !needs_panic_runtime {
             return;
         }
 
-        // By this point we know that we (a) need a panic runtime and (b) no
-        // panic runtime was explicitly linked. Here we just load an appropriate
-        // default runtime for our panic strategy and then inject the
-        // dependencies.
+        // By this point we know that we need a panic runtime. Here we just load
+        // an appropriate default runtime for our panic strategy.
         //
         // We may resolve to an already loaded crate (as the crate may not have
-        // been explicitly linked prior to this) and we may re-inject
-        // dependencies again, but both of those situations are fine.
+        // been explicitly linked prior to this), but this is fine.
         //
         // Also note that we have yet to perform validation of the crate graph
         // in terms of everyone has a compatible panic runtime format, that's
         // performed later as part of the `dependency_format` module.
+        let desired_strategy = self.sess.panic_strategy();
         let name = match desired_strategy {
             PanicStrategy::Unwind => sym::panic_unwind,
             PanicStrategy::Abort => sym::panic_abort,
@@ -1031,7 +997,6 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         }
 
         self.cstore.injected_panic_runtime = Some(cnum);
-        self.inject_dependency_if(cnum, "a panic runtime", &|data| data.needs_panic_runtime());
     }
 
     fn inject_profiler_runtime(&mut self) {
@@ -1212,45 +1177,6 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         }
     }
 
-    fn inject_dependency_if(
-        &mut self,
-        krate: CrateNum,
-        what: &str,
-        needs_dep: &dyn Fn(&CrateMetadata) -> bool,
-    ) {
-        // Don't perform this validation if the session has errors, as one of
-        // those errors may indicate a circular dependency which could cause
-        // this to stack overflow.
-        if self.dcx().has_errors().is_some() {
-            return;
-        }
-
-        // Before we inject any dependencies, make sure we don't inject a
-        // circular dependency by validating that this crate doesn't
-        // transitively depend on any crates satisfying `needs_dep`.
-        for dep in self.cstore.crate_dependencies_in_reverse_postorder(krate) {
-            let data = self.cstore.get_crate_data(dep);
-            if needs_dep(&data) {
-                self.dcx().emit_err(errors::NoTransitiveNeedsDep {
-                    crate_name: self.cstore.get_crate_data(krate).name(),
-                    needs_crate_name: what,
-                    deps_crate_name: data.name(),
-                });
-            }
-        }
-
-        // All crates satisfying `needs_dep` do not explicitly depend on the
-        // crate provided for this compile, but in order for this compilation to
-        // be successfully linked we need to inject a dependency (to order the
-        // crates on the command line correctly).
-        for (cnum, data) in self.cstore.iter_crate_data_mut() {
-            if needs_dep(data) {
-                info!("injecting a dep from {} to {}", cnum, krate);
-                data.add_dependency(krate);
-            }
-        }
-    }
-
     fn report_unused_deps(&mut self, krate: &ast::Crate) {
         // Make a point span rather than covering the whole file
         let span = krate.spans.inner_span.shrink_to_lo();