EIC code displayed by LXR master/​include/​clang/​AST/​Redeclarable.h	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2026-05-10 08:36:41

 //===- Redeclarable.h - Base for Decls that can be redeclared --*- C++ -*-====//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 //  This file defines the Redeclarable interface.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_AST_REDECLARABLE_H
 #define LLVM_CLANG_AST_REDECLARABLE_H
 
 #include "clang/AST/ExternalASTSource.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Casting.h"
 #include <cassert>
 #include <cstddef>
 #include <iterator>
 
 namespace clang {
 
 class ASTContext;
 class Decl;
 
 // Some notes on redeclarables:
 //
 //  - Every redeclarable is on a circular linked list.
 //
 //  - Every decl has a pointer to the first element of the chain _and_ a
 //    DeclLink that may point to one of 3 possible states:
 //      - the "previous" (temporal) element in the chain
 //      - the "latest" (temporal) element in the chain
 //      - the "uninitialized-latest" value (when newly-constructed)
 //
 //  - The first element is also often called the canonical element. Every
 //    element has a pointer to it so that "getCanonical" can be fast.
 //
 //  - Most links in the chain point to previous, except the link out of
 //    the first; it points to latest.
 //
 //  - Elements are called "first", "previous", "latest" or
 //    "most-recent" when referring to temporal order: order of addition
 //    to the chain.
 //
 //  - It's easiest to just ignore the implementation of DeclLink when making
 //    sense of the redeclaration chain.
 //
 //  - There's also a "definition" link for several types of
 //    redeclarable, where only one definition should exist at any given
 //    time (and the defn pointer is stored in the decl's "data" which
 //    is copied to every element on the chain when it's changed).
 //
 //    Here is some ASCII art:
 //
 //      "first"                                     "latest"
 //      "canonical"                                 "most recent"
 //      +------------+         first                +--------------+
 //      |            | <--------------------------- |              |
 //      |            |                              |              |
 //      |            |                              |              |
 //      |            |       +--------------+       |              |
 //      |            | first |              |       |              |
 //      |            | <---- |              |       |              |
 //      |            |       |              |       |              |
 //      | @class A   |  link | @interface A |  link | @class A     |
 //      | seen first | <---- | seen second  | <---- | seen third   |
 //      |            |       |              |       |              |
 //      +------------+       +--------------+       +--------------+
 //      | data       | defn  | data         |  defn | data         |
 //      |            | ----> |              | <---- |              |
 //      +------------+       +--------------+       +--------------+
 //        |                     |     ^                  ^
 //        |                     |defn |                  |
 //        | link                +-----+                  |
 //        +-->-------------------------------------------+
 
 /// Provides common interface for the Decls that can be redeclared.
 template<typename decl_type>
 class Redeclarable {
 protected:
   class DeclLink {
     /// A pointer to a known latest declaration, either statically known or
     /// generationally updated as decls are added by an external source.
     using KnownLatest =
         LazyGenerationalUpdatePtr<const Decl *, Decl *,
                                   &ExternalASTSource::CompleteRedeclChain>;
 
     /// We store a pointer to the ASTContext in the UninitializedLatest
     /// pointer, but to avoid circular type dependencies when we steal the low
     /// bits of this pointer, we use a raw void* here.
     using UninitializedLatest = const void *;
 
     using Previous = Decl *;
 
     /// A pointer to either an uninitialized latest declaration (where either
     /// we've not yet set the previous decl or there isn't one), or to a known
     /// previous declaration.
     using NotKnownLatest = llvm::PointerUnion<Previous, UninitializedLatest>;
 
     mutable llvm::PointerUnion<NotKnownLatest, KnownLatest> Link;
 
   public:
     enum PreviousTag { PreviousLink };
     enum LatestTag { LatestLink };
 
     DeclLink(LatestTag, const ASTContext &Ctx)
         : Link(NotKnownLatest(reinterpret_cast<UninitializedLatest>(&Ctx))) {}
     DeclLink(PreviousTag, decl_type *D) : Link(NotKnownLatest(Previous(D))) {}
 
     bool isFirst() const {
       return isa<KnownLatest>(Link) ||
              // FIXME: 'template' is required on the next line due to an
              // apparent clang bug.
              isa<UninitializedLatest>(cast<NotKnownLatest>(Link));
     }
 
     decl_type *getPrevious(const decl_type *D) const {
       if (NotKnownLatest NKL = dyn_cast<NotKnownLatest>(Link)) {
         if (auto *Prev = dyn_cast<Previous>(NKL))
           return static_cast<decl_type *>(Prev);
 
         // Allocate the generational 'most recent' cache now, if needed.
         Link = KnownLatest(*reinterpret_cast<const ASTContext *>(
                                cast<UninitializedLatest>(NKL)),
                            const_cast<decl_type *>(D));
       }
 
       return static_cast<decl_type *>(cast<KnownLatest>(Link).get(D));
     }
 
     void setPrevious(decl_type *D) {
       assert(!isFirst() && "decl became non-canonical unexpectedly");
       Link = Previous(D);
     }
 
     void setLatest(decl_type *D) {
       assert(isFirst() && "decl became canonical unexpectedly");
       if (NotKnownLatest NKL = dyn_cast<NotKnownLatest>(Link)) {
         Link = KnownLatest(*reinterpret_cast<const ASTContext *>(
                                cast<UninitializedLatest>(NKL)),
                            D);
       } else {
         auto Latest = cast<KnownLatest>(Link);
         Latest.set(D);
         Link = Latest;
       }
     }
 
     void markIncomplete() { cast<KnownLatest>(Link).markIncomplete(); }
 
     Decl *getLatestNotUpdated() const {
       assert(isFirst() && "expected a canonical decl");
       if (isa<NotKnownLatest>(Link))
         return nullptr;
       return cast<KnownLatest>(Link).getNotUpdated();
     }
   };
 
   static DeclLink PreviousDeclLink(decl_type *D) {
     return DeclLink(DeclLink::PreviousLink, D);
   }
 
   static DeclLink LatestDeclLink(const ASTContext &Ctx) {
     return DeclLink(DeclLink::LatestLink, Ctx);
   }
 
   /// Points to the next redeclaration in the chain.
   ///
   /// If isFirst() is false, this is a link to the previous declaration
   /// of this same Decl. If isFirst() is true, this is the first
   /// declaration and Link points to the latest declaration. For example:
   ///
   ///  #1 int f(int x, int y = 1); // <pointer to #3, true>
   ///  #2 int f(int x = 0, int y); // <pointer to #1, false>
   ///  #3 int f(int x, int y) { return x + y; } // <pointer to #2, false>
   ///
   /// If there is only one declaration, it is <pointer to self, true>
   DeclLink RedeclLink;
 
   decl_type *First;
 
   decl_type *getNextRedeclaration() const {
     return RedeclLink.getPrevious(static_cast<const decl_type *>(this));
   }
 
 public:
   friend class ASTDeclMerger;
   friend class ASTDeclReader;
   friend class ASTDeclWriter;
   friend class IncrementalParser;
 
   Redeclarable(const ASTContext &Ctx)
       : RedeclLink(LatestDeclLink(Ctx)),
         First(static_cast<decl_type *>(this)) {}
 
   /// Return the previous declaration of this declaration or NULL if this
   /// is the first declaration.
   decl_type *getPreviousDecl() {
     if (!RedeclLink.isFirst())
       return getNextRedeclaration();
     return nullptr;
   }
   const decl_type *getPreviousDecl() const {
     return const_cast<decl_type *>(
                  static_cast<const decl_type*>(this))->getPreviousDecl();
   }
 
   /// Return the first declaration of this declaration or itself if this
   /// is the only declaration.
   decl_type *getFirstDecl() { return First; }
 
   /// Return the first declaration of this declaration or itself if this
   /// is the only declaration.
   const decl_type *getFirstDecl() const { return First; }
 
   /// True if this is the first declaration in its redeclaration chain.
   bool isFirstDecl() const { return RedeclLink.isFirst(); }
 
   /// Returns the most recent (re)declaration of this declaration.
   decl_type *getMostRecentDecl() {
     return getFirstDecl()->getNextRedeclaration();
   }
 
   /// Returns the most recent (re)declaration of this declaration.
   const decl_type *getMostRecentDecl() const {
     return getFirstDecl()->getNextRedeclaration();
   }
 
   /// Set the previous declaration. If PrevDecl is NULL, set this as the
   /// first and only declaration.
   void setPreviousDecl(decl_type *PrevDecl);
 
   /// Iterates through all the redeclarations of the same decl.
   class redecl_iterator {
     /// Current - The current declaration.
     decl_type *Current = nullptr;
     decl_type *Starter = nullptr;
     bool PassedFirst = false;
 
   public:
     using value_type = decl_type *;
     using reference = decl_type *;
     using pointer = decl_type *;
     using iterator_category = std::forward_iterator_tag;
     using difference_type = std::ptrdiff_t;
 
     redecl_iterator() = default;
     explicit redecl_iterator(decl_type *C) : Current(C), Starter(C) {}
 
     reference operator*() const { return Current; }
     pointer operator->() const { return Current; }
 
     redecl_iterator& operator++() {
       assert(Current && "Advancing while iterator has reached end");
       // Make sure we don't infinitely loop on an invalid redecl chain. This
       // should never happen.
       if (Current->isFirstDecl()) {
         if (PassedFirst) {
           assert(0 && "Passed first decl twice, invalid redecl chain!");
           Current = nullptr;
           return *this;
         }
         PassedFirst = true;
       }
 
       // Get either previous decl or latest decl.
       decl_type *Next = Current->getNextRedeclaration();
       Current = (Next != Starter) ? Next : nullptr;
       return *this;
     }
 
     redecl_iterator operator++(int) {
       redecl_iterator tmp(*this);
       ++(*this);
       return tmp;
     }
 
     friend bool operator==(const redecl_iterator &x, const redecl_iterator &y) {
       return x.Current == y.Current;
     }
     friend bool operator!=(const redecl_iterator &x, const redecl_iterator &y) {
       return x.Current != y.Current;
     }
   };
 
   using redecl_range = llvm::iterator_range<redecl_iterator>;
 
   /// Returns an iterator range for all the redeclarations of the same
   /// decl. It will iterate at least once (when this decl is the only one).
   redecl_range redecls() const {
     return redecl_range(redecl_iterator(const_cast<decl_type *>(
                             static_cast<const decl_type *>(this))),
                         redecl_iterator());
   }
 
   redecl_iterator redecls_begin() const { return redecls().begin(); }
   redecl_iterator redecls_end() const { return redecls().end(); }
 };
 
 /// Get the primary declaration for a declaration from an AST file. That
 /// will be the first-loaded declaration.
 Decl *getPrimaryMergedDecl(Decl *D);
 
 /// Provides common interface for the Decls that cannot be redeclared,
 /// but can be merged if the same declaration is brought in from multiple
 /// modules.
 template<typename decl_type>
 class Mergeable {
 public:
   Mergeable() = default;
 
   /// Return the first declaration of this declaration or itself if this
   /// is the only declaration.
   decl_type *getFirstDecl() {
     auto *D = static_cast<decl_type *>(this);
     if (!D->isFromASTFile())
       return D;
     return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
   }
 
   /// Return the first declaration of this declaration or itself if this
   /// is the only declaration.
   const decl_type *getFirstDecl() const {
     const auto *D = static_cast<const decl_type *>(this);
     if (!D->isFromASTFile())
       return D;
     return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
   }
 
   /// Returns true if this is the first declaration.
   bool isFirstDecl() const { return getFirstDecl() == this; }
 };
 
 /// A wrapper class around a pointer that always points to its canonical
 /// declaration.
 ///
 /// CanonicalDeclPtr<decl_type> behaves just like decl_type*, except we call
 /// decl_type::getCanonicalDecl() on construction.
 ///
 /// This is useful for hashtables that you want to be keyed on a declaration's
 /// canonical decl -- if you use CanonicalDeclPtr as the key, you don't need to
 /// remember to call getCanonicalDecl() everywhere.
 template <typename decl_type> class CanonicalDeclPtr {
 public:
   CanonicalDeclPtr() = default;
   CanonicalDeclPtr(decl_type *Ptr)
       : Ptr(Ptr ? Ptr->getCanonicalDecl() : nullptr) {}
   CanonicalDeclPtr(const CanonicalDeclPtr &) = default;
   CanonicalDeclPtr &operator=(const CanonicalDeclPtr &) = default;
 
   operator decl_type *() { return Ptr; }
   operator const decl_type *() const { return Ptr; }
 
   decl_type *operator->() { return Ptr; }
   const decl_type *operator->() const { return Ptr; }
 
   decl_type &operator*() { return *Ptr; }
   const decl_type &operator*() const { return *Ptr; }
 
   friend bool operator==(CanonicalDeclPtr LHS, CanonicalDeclPtr RHS) {
     return LHS.Ptr == RHS.Ptr;
   }
   friend bool operator!=(CanonicalDeclPtr LHS, CanonicalDeclPtr RHS) {
     return LHS.Ptr != RHS.Ptr;
   }
 
 private:
   friend struct llvm::DenseMapInfo<CanonicalDeclPtr<decl_type>>;
   friend struct llvm::PointerLikeTypeTraits<CanonicalDeclPtr<decl_type>>;
 
   decl_type *Ptr = nullptr;
 };
 
 } // namespace clang
 
 namespace llvm {
 
 template <typename decl_type>
 struct DenseMapInfo<clang::CanonicalDeclPtr<decl_type>> {
   using CanonicalDeclPtr = clang::CanonicalDeclPtr<decl_type>;
   using BaseInfo = DenseMapInfo<decl_type *>;
 
   static CanonicalDeclPtr getEmptyKey() {
     // Construct our CanonicalDeclPtr this way because the regular constructor
     // would dereference P.Ptr, which is not allowed.
     CanonicalDeclPtr P;
     P.Ptr = BaseInfo::getEmptyKey();
     return P;
   }
 
   static CanonicalDeclPtr getTombstoneKey() {
     CanonicalDeclPtr P;
     P.Ptr = BaseInfo::getTombstoneKey();
     return P;
   }
 
   static unsigned getHashValue(const CanonicalDeclPtr &P) {
     return BaseInfo::getHashValue(P);
   }
 
   static bool isEqual(const CanonicalDeclPtr &LHS,
                       const CanonicalDeclPtr &RHS) {
     return BaseInfo::isEqual(LHS, RHS);
   }
 };
 
 template <typename decl_type>
 struct PointerLikeTypeTraits<clang::CanonicalDeclPtr<decl_type>> {
   static inline void *getAsVoidPointer(clang::CanonicalDeclPtr<decl_type> P) {
     return P.Ptr;
   }
   static inline clang::CanonicalDeclPtr<decl_type> getFromVoidPointer(void *P) {
     clang::CanonicalDeclPtr<decl_type> C;
     C.Ptr = PointerLikeTypeTraits<decl_type *>::getFromVoidPtr(P);
     return C;
   }
   static constexpr int NumLowBitsAvailable =
       PointerLikeTypeTraits<decl_type *>::NumLowBitsAvailable;
 };
 
 } // namespace llvm
 
 #endif // LLVM_CLANG_AST_REDECLARABLE_H

This page was automatically generated by the 2.3.7 LXR engine. The LXR team