Ownership.h revision 6bcf27bb9a4b5c3f79cb44c0e4654a6d7619ad89 
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/Basic/LLVM.h"
18#include "llvm/ADT/ArrayRef.h"
19#include "llvm/ADT/PointerIntPair.h"
20
21//===----------------------------------------------------------------------===//
22// OpaquePtr
23//===----------------------------------------------------------------------===//
24
25namespace clang {
26  class CXXCtorInitializer;
27  class CXXBaseSpecifier;
28  class Decl;
29  class Expr;
30  class ParsedTemplateArgument;
31  class QualType;
32  class Stmt;
33  class TemplateName;
34  class TemplateParameterList;
35
36  /// \brief Wrapper for void* pointer.
37  /// \tparam PtrTy Either a pointer type like 'T*' or a type that behaves like
38  ///               a pointer.
39  ///
40  /// This is a very simple POD type that wraps a pointer that the Parser
41  /// doesn't know about but that Sema or another client does.  The PtrTy
42  /// template argument is used to make sure that "Decl" pointers are not
43  /// compatible with "Type" pointers for example.
44  template <class PtrTy>
45  class OpaquePtr {
46    void *Ptr;
47    explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {}
48
49    typedef llvm::PointerLikeTypeTraits<PtrTy> Traits;
50
51  public:
52    OpaquePtr() : Ptr(nullptr) {}
53
54    static OpaquePtr make(PtrTy P) { OpaquePtr OP; OP.set(P); return OP; }
55
56    /// \brief Returns plain pointer to the entity pointed by this wrapper.
57    /// \tparam PointeeT Type of pointed entity.
58    ///
59    /// It is identical to getPtrAs<PointeeT*>.
60    template <typename PointeeT> PointeeT* getPtrTo() const {
61      return get();
62    }
63
64    /// \brief Returns pointer converted to the specified type.
65    /// \tparam PtrT Result pointer type.  There must be implicit conversion
66    ///              from PtrTy to PtrT.
67    ///
68    /// In contrast to getPtrTo, this method allows the return type to be
69    /// a smart pointer.
70    template <typename PtrT> PtrT getPtrAs() const {
71      return get();
72    }
73
74    PtrTy get() const {
75      return Traits::getFromVoidPointer(Ptr);
76    }
77
78    void set(PtrTy P) {
79      Ptr = Traits::getAsVoidPointer(P);
80    }
81
82    LLVM_EXPLICIT operator bool() const { return Ptr != nullptr; }
83
84    void *getAsOpaquePtr() const { return Ptr; }
85    static OpaquePtr getFromOpaquePtr(void *P) { return OpaquePtr(P); }
86  };
87
88  /// UnionOpaquePtr - A version of OpaquePtr suitable for membership
89  /// in a union.
90  template <class T> struct UnionOpaquePtr {
91    void *Ptr;
92
93    static UnionOpaquePtr make(OpaquePtr<T> P) {
94      UnionOpaquePtr OP = { P.getAsOpaquePtr() };
95      return OP;
96    }
97
98    OpaquePtr<T> get() const { return OpaquePtr<T>::getFromOpaquePtr(Ptr); }
99    operator OpaquePtr<T>() const { return get(); }
100
101    UnionOpaquePtr &operator=(OpaquePtr<T> P) {
102      Ptr = P.getAsOpaquePtr();
103      return *this;
104    }
105  };
106}
107
108namespace llvm {
109  template <class T>
110  class PointerLikeTypeTraits<clang::OpaquePtr<T> > {
111  public:
112    static inline void *getAsVoidPointer(clang::OpaquePtr<T> P) {
113      // FIXME: Doesn't work? return P.getAs< void >();
114      return P.getAsOpaquePtr();
115    }
116    static inline clang::OpaquePtr<T> getFromVoidPointer(void *P) {
117      return clang::OpaquePtr<T>::getFromOpaquePtr(P);
118    }
119    enum { NumLowBitsAvailable = 0 };
120  };
121
122  template <class T>
123  struct isPodLike<clang::OpaquePtr<T> > { static const bool value = true; };
124}
125
126namespace clang {
127  // Basic
128  class DiagnosticBuilder;
129
130  // Determines whether the low bit of the result pointer for the
131  // given UID is always zero. If so, ActionResult will use that bit
132  // for it's "invalid" flag.
133  template<class Ptr>
134  struct IsResultPtrLowBitFree {
135    static const bool value = false;
136  };
137
138  /// ActionResult - This structure is used while parsing/acting on
139  /// expressions, stmts, etc.  It encapsulates both the object returned by
140  /// the action, plus a sense of whether or not it is valid.
141  /// When CompressInvalid is true, the "invalid" flag will be
142  /// stored in the low bit of the Val pointer.
143  template<class PtrTy,
144           bool CompressInvalid = IsResultPtrLowBitFree<PtrTy>::value>
145  class ActionResult {
146    PtrTy Val;
147    bool Invalid;
148
149  public:
150    ActionResult(bool Invalid = false)
151      : Val(PtrTy()), Invalid(Invalid) {}
152    ActionResult(PtrTy val) : Val(val), Invalid(false) {}
153    ActionResult(const DiagnosticBuilder &) : Val(PtrTy()), Invalid(true) {}
154
155    // These two overloads prevent void* -> bool conversions.
156    ActionResult(const void *);
157    ActionResult(volatile void *);
158
159    bool isInvalid() const { return Invalid; }
160    bool isUsable() const { return !Invalid && Val; }
161    bool isUnset() const { return !Invalid && !Val; }
162
163    PtrTy get() const { return Val; }
164    // FIXME: Replace with get.
165    PtrTy release() const { return Val; }
166    PtrTy take() const { return Val; }
167    template <typename T> T *takeAs() { return static_cast<T*>(get()); }
168
169    void set(PtrTy V) { Val = V; }
170
171    const ActionResult &operator=(PtrTy RHS) {
172      Val = RHS;
173      Invalid = false;
174      return *this;
175    }
176  };
177
178  // This ActionResult partial specialization places the "invalid"
179  // flag into the low bit of the pointer.
180  template<typename PtrTy>
181  class ActionResult<PtrTy, true> {
182    // A pointer whose low bit is 1 if this result is invalid, 0
183    // otherwise.
184    uintptr_t PtrWithInvalid;
185    typedef llvm::PointerLikeTypeTraits<PtrTy> PtrTraits;
186  public:
187    ActionResult(bool Invalid = false)
188      : PtrWithInvalid(static_cast<uintptr_t>(Invalid)) { }
189
190    ActionResult(PtrTy V) {
191      void *VP = PtrTraits::getAsVoidPointer(V);
192      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
193      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
194    }
195    ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) { }
196
197    // These two overloads prevent void* -> bool conversions.
198    ActionResult(const void *);
199    ActionResult(volatile void *);
200
201    bool isInvalid() const { return PtrWithInvalid & 0x01; }
202    bool isUsable() const { return PtrWithInvalid > 0x01; }
203    bool isUnset() const { return PtrWithInvalid == 0; }
204
205    PtrTy get() const {
206      void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01);
207      return PtrTraits::getFromVoidPointer(VP);
208    }
209    // FIXME: Replace with get.
210    PtrTy take() const { return get(); }
211    PtrTy release() const { return get(); }
212    template <typename T> T *takeAs() { return static_cast<T*>(get()); }
213
214    void set(PtrTy V) {
215      void *VP = PtrTraits::getAsVoidPointer(V);
216      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
217      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
218    }
219
220    const ActionResult &operator=(PtrTy RHS) {
221      void *VP = PtrTraits::getAsVoidPointer(RHS);
222      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
223      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
224      return *this;
225    }
226
227    // For types where we can fit a flag in with the pointer, provide
228    // conversions to/from pointer type.
229    static ActionResult getFromOpaquePointer(void *P) {
230      ActionResult Result;
231      Result.PtrWithInvalid = (uintptr_t)P;
232      return Result;
233    }
234    void *getAsOpaquePointer() const { return (void*)PtrWithInvalid; }
235  };
236
237  /// An opaque type for threading parsed type information through the
238  /// parser.
239  typedef OpaquePtr<QualType> ParsedType;
240  typedef UnionOpaquePtr<QualType> UnionParsedType;
241
242  // We can re-use the low bit of expression, statement, base, and
243  // member-initializer pointers for the "invalid" flag of
244  // ActionResult.
245  template<> struct IsResultPtrLowBitFree<Expr*> {
246    static const bool value = true;
247  };
248  template<> struct IsResultPtrLowBitFree<Stmt*> {
249    static const bool value = true;
250  };
251  template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> {
252    static const bool value = true;
253  };
254  template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> {
255    static const bool value = true;
256  };
257
258  typedef ActionResult<Expr*> ExprResult;
259  typedef ActionResult<Stmt*> StmtResult;
260  typedef ActionResult<ParsedType> TypeResult;
261  typedef ActionResult<CXXBaseSpecifier*> BaseResult;
262  typedef ActionResult<CXXCtorInitializer*> MemInitResult;
263
264  typedef ActionResult<Decl*> DeclResult;
265  typedef OpaquePtr<TemplateName> ParsedTemplateTy;
266
267  typedef llvm::MutableArrayRef<Expr*> MultiExprArg;
268  typedef llvm::MutableArrayRef<Stmt*> MultiStmtArg;
269  typedef llvm::MutableArrayRef<ParsedTemplateArgument> ASTTemplateArgsPtr;
270  typedef llvm::MutableArrayRef<ParsedType> MultiTypeArg;
271  typedef llvm::MutableArrayRef<TemplateParameterList*> MultiTemplateParamsArg;
272
273  inline ExprResult ExprError() { return ExprResult(true); }
274  inline StmtResult StmtError() { return StmtResult(true); }
275
276  inline ExprResult ExprError(const DiagnosticBuilder&) { return ExprError(); }
277  inline StmtResult StmtError(const DiagnosticBuilder&) { return StmtError(); }
278
279  inline ExprResult ExprEmpty() { return ExprResult(false); }
280  inline StmtResult StmtEmpty() { return StmtResult(false); }
281
282  inline Expr *AssertSuccess(ExprResult R) {
283    assert(!R.isInvalid() && "operation was asserted to never fail!");
284    return R.get();
285  }
286
287  inline Stmt *AssertSuccess(StmtResult R) {
288    assert(!R.isInvalid() && "operation was asserted to never fail!");
289    return R.get();
290  }
291}
292
293#endif
294