1 //===- Core/Atom.h - A node in linking graph --------------------*- C++ -*-===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLD_CORE_ATOM_H
11 #define LLD_CORE_ATOM_H
13 #include "lld/Core/LLVM.h"
14 #include "llvm/ADT/StringRef.h"
24 /// The linker has a Graph Theory model of linking. An object file is seen
25 /// as a set of Atoms with References to other Atoms. Each Atom is a node
26 /// and each Reference is an edge. An Atom can be a DefinedAtom which has
27 /// content or a UndefinedAtom which is a placeholder and represents an
28 /// undefined symbol (extern declaration).
31 template<typename T> friend class OwningAtomPtr;
34 /// Whether this atom is defined or a proxy for an undefined symbol
36 definitionRegular, ///< Normal C/C++ function or global variable.
37 definitionAbsolute, ///< Asm-only (foo = 10). Not tied to any content.
38 definitionUndefined, ///< Only in .o files to model reference to undef.
39 definitionSharedLibrary ///< Only in shared libraries to model export.
42 /// The scope in which this atom is acessible to other atoms.
44 scopeTranslationUnit, ///< Accessible only to atoms in the same translation
45 /// unit (e.g. a C static).
46 scopeLinkageUnit, ///< Accessible to atoms being linked but not visible
47 /// to runtime loader (e.g. visibility=hidden).
48 scopeGlobal ///< Accessible to all atoms and visible to runtime
49 /// loader (e.g. visibility=default).
52 /// file - returns the File that produced/owns this Atom
53 virtual const File& file() const = 0;
55 /// name - The name of the atom. For a function atom, it is the (mangled)
56 /// name of the function.
57 virtual StringRef name() const = 0;
59 /// definition - Whether this atom is a definition or represents an undefined
61 Definition definition() const { return _definition; }
63 static bool classof(const Atom *a) { return true; }
66 /// Atom is an abstract base class. Only subclasses can access constructor.
67 explicit Atom(Definition def) : _definition(def) {}
69 /// The memory for Atom objects is always managed by the owning File
70 /// object. Therefore, no one but the owning File object should call
71 /// delete on an Atom. In fact, some File objects may bulk allocate
72 /// an array of Atoms, so they cannot be individually deleted by anyone.
73 virtual ~Atom() = default;
76 Definition _definition;
79 /// Class which owns an atom pointer and runs the atom destructor when the
80 /// owning pointer goes out of scope.
84 OwningAtomPtr(const OwningAtomPtr &) = delete;
85 void operator=(const OwningAtomPtr &) = delete;
88 OwningAtomPtr() = default;
89 OwningAtomPtr(T *atom) : atom(atom) { }
96 void runDestructor(Atom *atom) {
100 OwningAtomPtr(OwningAtomPtr &&ptr) : atom(ptr.atom) {
104 void operator=(OwningAtomPtr&& ptr) {
111 T *const &get() const {
129 } // end namespace lld
131 #endif // LLD_CORE_ATOM_H