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
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 = nullptr;
47    explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {}
48
49    typedef llvm::PointerLikeTypeTraits<PtrTy> Traits;
50
51  public:
52    OpaquePtr(std::nullptr_t = 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    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 *) = delete;
157    ActionResult(volatile void *) = delete;
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    template <typename T> T *getAs() { return static_cast<T*>(get()); }
165
166    void set(PtrTy V) { Val = V; }
167
168    const ActionResult &operator=(PtrTy RHS) {
169      Val = RHS;
170      Invalid = false;
171      return *this;
172    }
173  };
174
175  // This ActionResult partial specialization places the "invalid"
176  // flag into the low bit of the pointer.
177  template<typename PtrTy>
178  class ActionResult<PtrTy, true> {
179    // A pointer whose low bit is 1 if this result is invalid, 0
180    // otherwise.
181    uintptr_t PtrWithInvalid;
182    typedef llvm::PointerLikeTypeTraits<PtrTy> PtrTraits;
183  public:
184    ActionResult(bool Invalid = false)
185      : PtrWithInvalid(static_cast<uintptr_t>(Invalid)) { }
186
187    ActionResult(PtrTy V) {
188      void *VP = PtrTraits::getAsVoidPointer(V);
189      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
190      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
191    }
192    ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) { }
193
194    // These two overloads prevent void* -> bool conversions.
195    ActionResult(const void *) = delete;
196    ActionResult(volatile void *) = delete;
197
198    bool isInvalid() const { return PtrWithInvalid & 0x01; }
199    bool isUsable() const { return PtrWithInvalid > 0x01; }
200    bool isUnset() const { return PtrWithInvalid == 0; }
201
202    PtrTy get() const {
203      void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01);
204      return PtrTraits::getFromVoidPointer(VP);
205    }
206    template <typename T> T *getAs() { return static_cast<T*>(get()); }
207
208    void set(PtrTy V) {
209      void *VP = PtrTraits::getAsVoidPointer(V);
210      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
211      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
212    }
213
214    const ActionResult &operator=(PtrTy RHS) {
215      void *VP = PtrTraits::getAsVoidPointer(RHS);
216      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
217      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
218      return *this;
219    }
220
221    // For types where we can fit a flag in with the pointer, provide
222    // conversions to/from pointer type.
223    static ActionResult getFromOpaquePointer(void *P) {
224      ActionResult Result;
225      Result.PtrWithInvalid = (uintptr_t)P;
226      return Result;
227    }
228    void *getAsOpaquePointer() const { return (void*)PtrWithInvalid; }
229  };
230
231  /// An opaque type for threading parsed type information through the
232  /// parser.
233  typedef OpaquePtr<QualType> ParsedType;
234  typedef UnionOpaquePtr<QualType> UnionParsedType;
235
236  // We can re-use the low bit of expression, statement, base, and
237  // member-initializer pointers for the "invalid" flag of
238  // ActionResult.
239  template<> struct IsResultPtrLowBitFree<Expr*> {
240    static const bool value = true;
241  };
242  template<> struct IsResultPtrLowBitFree<Stmt*> {
243    static const bool value = true;
244  };
245  template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> {
246    static const bool value = true;
247  };
248  template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> {
249    static const bool value = true;
250  };
251
252  typedef ActionResult<Expr*> ExprResult;
253  typedef ActionResult<Stmt*> StmtResult;
254  typedef ActionResult<ParsedType> TypeResult;
255  typedef ActionResult<CXXBaseSpecifier*> BaseResult;
256  typedef ActionResult<CXXCtorInitializer*> MemInitResult;
257
258  typedef ActionResult<Decl*> DeclResult;
259  typedef OpaquePtr<TemplateName> ParsedTemplateTy;
260  typedef UnionOpaquePtr<TemplateName> UnionParsedTemplateTy;
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