1//===--- Ownership.h - Parser ownership helpers -----------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file contains classes for managing ownership of Stmt and Expr nodes.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_SEMA_OWNERSHIP_H
15#define LLVM_CLANG_SEMA_OWNERSHIP_H
16
17#include "clang/AST/Expr.h"
18#include "clang/Basic/LLVM.h"
19#include "llvm/ADT/ArrayRef.h"
20#include "llvm/ADT/PointerIntPair.h"
21
22//===----------------------------------------------------------------------===//
23// OpaquePtr
24//===----------------------------------------------------------------------===//
25
26namespace clang {
27  class CXXCtorInitializer;
28  class CXXBaseSpecifier;
29  class Decl;
30  class Expr;
31  class ParsedTemplateArgument;
32  class QualType;
33  class Stmt;
34  class TemplateName;
35  class TemplateParameterList;
36
37  /// \brief Wrapper for void* pointer.
38  /// \tparam PtrTy Either a pointer type like 'T*' or a type that behaves like
39  ///               a pointer.
40  ///
41  /// This is a very simple POD type that wraps a pointer that the Parser
42  /// doesn't know about but that Sema or another client does.  The PtrTy
43  /// template argument is used to make sure that "Decl" pointers are not
44  /// compatible with "Type" pointers for example.
45  template <class PtrTy>
46  class OpaquePtr {
47    void *Ptr = nullptr;
48    explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {}
49
50    typedef llvm::PointerLikeTypeTraits<PtrTy> Traits;
51
52  public:
53    OpaquePtr(std::nullptr_t = nullptr) {}
54
55    static OpaquePtr make(PtrTy P) { OpaquePtr OP; OP.set(P); return OP; }
56
57    /// \brief Returns plain pointer to the entity pointed by this wrapper.
58    /// \tparam PointeeT Type of pointed entity.
59    ///
60    /// It is identical to getPtrAs<PointeeT*>.
61    template <typename PointeeT> PointeeT* getPtrTo() const {
62      return get();
63    }
64
65    /// \brief Returns pointer converted to the specified type.
66    /// \tparam PtrT Result pointer type.  There must be implicit conversion
67    ///              from PtrTy to PtrT.
68    ///
69    /// In contrast to getPtrTo, this method allows the return type to be
70    /// a smart pointer.
71    template <typename PtrT> PtrT getPtrAs() const {
72      return get();
73    }
74
75    PtrTy get() const {
76      return Traits::getFromVoidPointer(Ptr);
77    }
78
79    void set(PtrTy P) {
80      Ptr = Traits::getAsVoidPointer(P);
81    }
82
83    explicit operator bool() const { return Ptr != nullptr; }
84
85    void *getAsOpaquePtr() const { return Ptr; }
86    static OpaquePtr getFromOpaquePtr(void *P) { return OpaquePtr(P); }
87  };
88
89  /// UnionOpaquePtr - A version of OpaquePtr suitable for membership
90  /// in a union.
91  template <class T> struct UnionOpaquePtr {
92    void *Ptr;
93
94    static UnionOpaquePtr make(OpaquePtr<T> P) {
95      UnionOpaquePtr OP = { P.getAsOpaquePtr() };
96      return OP;
97    }
98
99    OpaquePtr<T> get() const { return OpaquePtr<T>::getFromOpaquePtr(Ptr); }
100    operator OpaquePtr<T>() const { return get(); }
101
102    UnionOpaquePtr &operator=(OpaquePtr<T> P) {
103      Ptr = P.getAsOpaquePtr();
104      return *this;
105    }
106  };
107}
108
109namespace llvm {
110  template <class T>
111  class PointerLikeTypeTraits<clang::OpaquePtr<T> > {
112  public:
113    static inline void *getAsVoidPointer(clang::OpaquePtr<T> P) {
114      // FIXME: Doesn't work? return P.getAs< void >();
115      return P.getAsOpaquePtr();
116    }
117    static inline clang::OpaquePtr<T> getFromVoidPointer(void *P) {
118      return clang::OpaquePtr<T>::getFromOpaquePtr(P);
119    }
120    enum { NumLowBitsAvailable = 0 };
121  };
122
123  template <class T>
124  struct isPodLike<clang::OpaquePtr<T> > { static const bool value = true; };
125}
126
127namespace clang {
128  // Basic
129  class DiagnosticBuilder;
130
131  // Determines whether the low bit of the result pointer for the
132  // given UID is always zero. If so, ActionResult will use that bit
133  // for it's "invalid" flag.
134  template<class Ptr>
135  struct IsResultPtrLowBitFree {
136    static const bool value = false;
137  };
138
139  /// ActionResult - This structure is used while parsing/acting on
140  /// expressions, stmts, etc.  It encapsulates both the object returned by
141  /// the action, plus a sense of whether or not it is valid.
142  /// When CompressInvalid is true, the "invalid" flag will be
143  /// stored in the low bit of the Val pointer.
144  template<class PtrTy,
145           bool CompressInvalid = IsResultPtrLowBitFree<PtrTy>::value>
146  class ActionResult {
147    PtrTy Val;
148    bool Invalid;
149
150  public:
151    ActionResult(bool Invalid = false)
152      : Val(PtrTy()), Invalid(Invalid) {}
153    ActionResult(PtrTy val) : Val(val), Invalid(false) {}
154    ActionResult(const DiagnosticBuilder &) : Val(PtrTy()), Invalid(true) {}
155
156    // These two overloads prevent void* -> bool conversions.
157    ActionResult(const void *);
158    ActionResult(volatile void *);
159
160    bool isInvalid() const { return Invalid; }
161    bool isUsable() const { return !Invalid && Val; }
162    bool isUnset() const { return !Invalid && !Val; }
163
164    PtrTy get() const { return Val; }
165    template <typename T> T *getAs() { return static_cast<T*>(get()); }
166
167    void set(PtrTy V) { Val = V; }
168
169    const ActionResult &operator=(PtrTy RHS) {
170      Val = RHS;
171      Invalid = false;
172      return *this;
173    }
174  };
175
176  // This ActionResult partial specialization places the "invalid"
177  // flag into the low bit of the pointer.
178  template<typename PtrTy>
179  class ActionResult<PtrTy, true> {
180    // A pointer whose low bit is 1 if this result is invalid, 0
181    // otherwise.
182    uintptr_t PtrWithInvalid;
183    typedef llvm::PointerLikeTypeTraits<PtrTy> PtrTraits;
184  public:
185    ActionResult(bool Invalid = false)
186      : PtrWithInvalid(static_cast<uintptr_t>(Invalid)) { }
187
188    ActionResult(PtrTy V) {
189      void *VP = PtrTraits::getAsVoidPointer(V);
190      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
191      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
192    }
193    ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) { }
194
195    // These two overloads prevent void* -> bool conversions.
196    ActionResult(const void *);
197    ActionResult(volatile void *);
198
199    bool isInvalid() const { return PtrWithInvalid & 0x01; }
200    bool isUsable() const { return PtrWithInvalid > 0x01; }
201    bool isUnset() const { return PtrWithInvalid == 0; }
202
203    PtrTy get() const {
204      void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01);
205      return PtrTraits::getFromVoidPointer(VP);
206    }
207    template <typename T> T *getAs() { return static_cast<T*>(get()); }
208
209    void set(PtrTy V) {
210      void *VP = PtrTraits::getAsVoidPointer(V);
211      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
212      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
213    }
214
215    const ActionResult &operator=(PtrTy RHS) {
216      void *VP = PtrTraits::getAsVoidPointer(RHS);
217      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
218      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
219      return *this;
220    }
221
222    // For types where we can fit a flag in with the pointer, provide
223    // conversions to/from pointer type.
224    static ActionResult getFromOpaquePointer(void *P) {
225      ActionResult Result;
226      Result.PtrWithInvalid = (uintptr_t)P;
227      return Result;
228    }
229    void *getAsOpaquePointer() const { return (void*)PtrWithInvalid; }
230  };
231
232  /// An opaque type for threading parsed type information through the
233  /// parser.
234  typedef OpaquePtr<QualType> ParsedType;
235  typedef UnionOpaquePtr<QualType> UnionParsedType;
236
237  // We can re-use the low bit of expression, statement, base, and
238  // member-initializer pointers for the "invalid" flag of
239  // ActionResult.
240  template<> struct IsResultPtrLowBitFree<Expr*> {
241    static const bool value = true;
242  };
243  template<> struct IsResultPtrLowBitFree<Stmt*> {
244    static const bool value = true;
245  };
246  template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> {
247    static const bool value = true;
248  };
249  template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> {
250    static const bool value = true;
251  };
252
253  typedef ActionResult<Expr*> ExprResult;
254  typedef ActionResult<Stmt*> StmtResult;
255  typedef ActionResult<ParsedType> TypeResult;
256  typedef ActionResult<CXXBaseSpecifier*> BaseResult;
257  typedef ActionResult<CXXCtorInitializer*> MemInitResult;
258
259  typedef ActionResult<Decl*> DeclResult;
260  typedef OpaquePtr<TemplateName> ParsedTemplateTy;
261
262  typedef MutableArrayRef<Expr*> MultiExprArg;
263  typedef MutableArrayRef<Stmt*> MultiStmtArg;
264  typedef MutableArrayRef<ParsedTemplateArgument> ASTTemplateArgsPtr;
265  typedef MutableArrayRef<ParsedType> MultiTypeArg;
266  typedef MutableArrayRef<TemplateParameterList*> MultiTemplateParamsArg;
267
268  inline ExprResult ExprError() { return ExprResult(true); }
269  inline StmtResult StmtError() { return StmtResult(true); }
270
271  inline ExprResult ExprError(const DiagnosticBuilder&) { return ExprError(); }
272  inline StmtResult StmtError(const DiagnosticBuilder&) { return StmtError(); }
273
274  inline ExprResult ExprEmpty() { return ExprResult(false); }
275  inline StmtResult StmtEmpty() { return StmtResult(false); }
276
277  inline Expr *AssertSuccess(ExprResult R) {
278    assert(!R.isInvalid() && "operation was asserted to never fail!");
279    return R.get();
280  }
281
282  inline Stmt *AssertSuccess(StmtResult R) {
283    assert(!R.isInvalid() && "operation was asserted to never fail!");
284    return R.get();
285  }
286}
287
288#endif
289