1//===- Ownership.h - Parser ownership helpers -------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9//  This file contains classes for managing ownership of Stmt and Expr nodes.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_SEMA_OWNERSHIP_H
14#define LLVM_CLANG_SEMA_OWNERSHIP_H
15
16#include "clang/AST/Expr.h"
17#include "clang/Basic/LLVM.h"
18#include "llvm/ADT/ArrayRef.h"
19#include "llvm/Support/PointerLikeTypeTraits.h"
20#include "llvm/Support/type_traits.h"
21#include <cassert>
22#include <cstddef>
23#include <cstdint>
24
25//===----------------------------------------------------------------------===//
26// OpaquePtr
27//===----------------------------------------------------------------------===//
28
29namespace clang {
30
31class CXXBaseSpecifier;
32class CXXCtorInitializer;
33class Decl;
34class Expr;
35class ParsedTemplateArgument;
36class QualType;
37class Stmt;
38class TemplateName;
39class TemplateParameterList;
40
41  /// Wrapper for void* pointer.
42  /// \tparam PtrTy Either a pointer type like 'T*' or a type that behaves like
43  ///               a pointer.
44  ///
45  /// This is a very simple POD type that wraps a pointer that the Parser
46  /// doesn't know about but that Sema or another client does.  The PtrTy
47  /// template argument is used to make sure that "Decl" pointers are not
48  /// compatible with "Type" pointers for example.
49  template <class PtrTy>
50  class OpaquePtr {
51    void *Ptr = nullptr;
52
53    explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {}
54
55    using Traits = llvm::PointerLikeTypeTraits<PtrTy>;
56
57  public:
58    OpaquePtr(std::nullptr_t = nullptr) {}
59
60    static OpaquePtr make(PtrTy P) { OpaquePtr OP; OP.set(P); return OP; }
61
62    /// Returns plain pointer to the entity pointed by this wrapper.
63    /// \tparam PointeeT Type of pointed entity.
64    ///
65    /// It is identical to getPtrAs<PointeeT*>.
66    template <typename PointeeT> PointeeT* getPtrTo() const {
67      return get();
68    }
69
70    /// Returns pointer converted to the specified type.
71    /// \tparam PtrT Result pointer type.  There must be implicit conversion
72    ///              from PtrTy to PtrT.
73    ///
74    /// In contrast to getPtrTo, this method allows the return type to be
75    /// a smart pointer.
76    template <typename PtrT> PtrT getPtrAs() const {
77      return get();
78    }
79
80    PtrTy get() const {
81      return Traits::getFromVoidPointer(Ptr);
82    }
83
84    void set(PtrTy P) {
85      Ptr = Traits::getAsVoidPointer(P);
86    }
87
88    explicit operator bool() const { return Ptr != nullptr; }
89
90    void *getAsOpaquePtr() const { return Ptr; }
91    static OpaquePtr getFromOpaquePtr(void *P) { return OpaquePtr(P); }
92  };
93
94  /// UnionOpaquePtr - A version of OpaquePtr suitable for membership
95  /// in a union.
96  template <class T> struct UnionOpaquePtr {
97    void *Ptr;
98
99    static UnionOpaquePtr make(OpaquePtr<T> P) {
100      UnionOpaquePtr OP = { P.getAsOpaquePtr() };
101      return OP;
102    }
103
104    OpaquePtr<T> get() const { return OpaquePtr<T>::getFromOpaquePtr(Ptr); }
105    operator OpaquePtr<T>() const { return get(); }
106
107    UnionOpaquePtr &operator=(OpaquePtr<T> P) {
108      Ptr = P.getAsOpaquePtr();
109      return *this;
110    }
111  };
112
113} // namespace clang
114
115namespace llvm {
116
117  template <class T>
118  struct PointerLikeTypeTraits<clang::OpaquePtr<T>> {
119    static constexpr int NumLowBitsAvailable = 0;
120
121    static inline void *getAsVoidPointer(clang::OpaquePtr<T> P) {
122      // FIXME: Doesn't work? return P.getAs< void >();
123      return P.getAsOpaquePtr();
124    }
125
126    static inline clang::OpaquePtr<T> getFromVoidPointer(void *P) {
127      return clang::OpaquePtr<T>::getFromOpaquePtr(P);
128    }
129  };
130
131} // namespace llvm
132
133namespace clang {
134
135  // Basic
136class StreamingDiagnostic;
137
138// Determines whether the low bit of the result pointer for the
139// given UID is always zero. If so, ActionResult will use that bit
140// for it's "invalid" flag.
141template <class Ptr> struct IsResultPtrLowBitFree {
142  static const bool value = false;
143  };
144
145  /// ActionResult - This structure is used while parsing/acting on
146  /// expressions, stmts, etc.  It encapsulates both the object returned by
147  /// the action, plus a sense of whether or not it is valid.
148  /// When CompressInvalid is true, the "invalid" flag will be
149  /// stored in the low bit of the Val pointer.
150  template<class PtrTy,
151           bool CompressInvalid = IsResultPtrLowBitFree<PtrTy>::value>
152  class ActionResult {
153    PtrTy Val;
154    bool Invalid;
155
156  public:
157    ActionResult(bool Invalid = false) : Val(PtrTy()), Invalid(Invalid) {}
158    ActionResult(PtrTy val) : Val(val), Invalid(false) {}
159    ActionResult(const DiagnosticBuilder &) : Val(PtrTy()), Invalid(true) {}
160
161    // These two overloads prevent void* -> bool conversions.
162    ActionResult(const void *) = delete;
163    ActionResult(volatile void *) = delete;
164
165    bool isInvalid() const { return Invalid; }
166    bool isUsable() const { return !Invalid && Val; }
167    bool isUnset() const { return !Invalid && !Val; }
168
169    PtrTy get() const { return Val; }
170    template <typename T> T *getAs() { return static_cast<T*>(get()); }
171
172    void set(PtrTy V) { Val = V; }
173
174    const ActionResult &operator=(PtrTy RHS) {
175      Val = RHS;
176      Invalid = false;
177      return *this;
178    }
179  };
180
181  // This ActionResult partial specialization places the "invalid"
182  // flag into the low bit of the pointer.
183  template<typename PtrTy>
184  class ActionResult<PtrTy, true> {
185    // A pointer whose low bit is 1 if this result is invalid, 0
186    // otherwise.
187    uintptr_t PtrWithInvalid;
188
189    using PtrTraits = llvm::PointerLikeTypeTraits<PtrTy>;
190
191  public:
192    ActionResult(bool Invalid = false)
193        : PtrWithInvalid(static_cast<uintptr_t>(Invalid)) {}
194
195    ActionResult(PtrTy V) {
196      void *VP = PtrTraits::getAsVoidPointer(V);
197      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
198      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
199    }
200
201    ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) {}
202
203    // These two overloads prevent void* -> bool conversions.
204    ActionResult(const void *) = delete;
205    ActionResult(volatile void *) = delete;
206
207    bool isInvalid() const { return PtrWithInvalid & 0x01; }
208    bool isUsable() const { return PtrWithInvalid > 0x01; }
209    bool isUnset() const { return PtrWithInvalid == 0; }
210
211    PtrTy get() const {
212      void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01);
213      return PtrTraits::getFromVoidPointer(VP);
214    }
215
216    template <typename T> T *getAs() { return static_cast<T*>(get()); }
217
218    void set(PtrTy V) {
219      void *VP = PtrTraits::getAsVoidPointer(V);
220      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
221      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
222    }
223
224    const ActionResult &operator=(PtrTy RHS) {
225      void *VP = PtrTraits::getAsVoidPointer(RHS);
226      PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
227      assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
228      return *this;
229    }
230
231    // For types where we can fit a flag in with the pointer, provide
232    // conversions to/from pointer type.
233    static ActionResult getFromOpaquePointer(void *P) {
234      ActionResult Result;
235      Result.PtrWithInvalid = (uintptr_t)P;
236      return Result;
237    }
238    void *getAsOpaquePointer() const { return (void*)PtrWithInvalid; }
239  };
240
241  /// An opaque type for threading parsed type information through the
242  /// parser.
243  using ParsedType = OpaquePtr<QualType>;
244  using UnionParsedType = UnionOpaquePtr<QualType>;
245
246  // We can re-use the low bit of expression, statement, base, and
247  // member-initializer pointers for the "invalid" flag of
248  // ActionResult.
249  template<> struct IsResultPtrLowBitFree<Expr*> {
250    static const bool value = true;
251  };
252  template<> struct IsResultPtrLowBitFree<Stmt*> {
253    static const bool value = true;
254  };
255  template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> {
256    static const bool value = true;
257  };
258  template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> {
259    static const bool value = true;
260  };
261
262  using ExprResult = ActionResult<Expr *>;
263  using StmtResult = ActionResult<Stmt *>;
264  using TypeResult = ActionResult<ParsedType>;
265  using BaseResult = ActionResult<CXXBaseSpecifier *>;
266  using MemInitResult = ActionResult<CXXCtorInitializer *>;
267
268  using DeclResult = ActionResult<Decl *>;
269  using ParsedTemplateTy = OpaquePtr<TemplateName>;
270  using UnionParsedTemplateTy = UnionOpaquePtr<TemplateName>;
271
272  using MultiExprArg = MutableArrayRef<Expr *>;
273  using MultiStmtArg = MutableArrayRef<Stmt *>;
274  using ASTTemplateArgsPtr = MutableArrayRef<ParsedTemplateArgument>;
275  using MultiTypeArg = MutableArrayRef<ParsedType>;
276  using MultiTemplateParamsArg = MutableArrayRef<TemplateParameterList *>;
277
278  inline ExprResult ExprError() { return ExprResult(true); }
279  inline StmtResult StmtError() { return StmtResult(true); }
280  inline TypeResult TypeError() { return TypeResult(true); }
281
282  inline ExprResult ExprError(const StreamingDiagnostic &) {
283    return ExprError();
284  }
285  inline StmtResult StmtError(const StreamingDiagnostic &) {
286    return StmtError();
287  }
288
289  inline ExprResult ExprEmpty() { return ExprResult(false); }
290  inline StmtResult StmtEmpty() { return StmtResult(false); }
291
292  inline Expr *AssertSuccess(ExprResult R) {
293    assert(!R.isInvalid() && "operation was asserted to never fail!");
294    return R.get();
295  }
296
297  inline Stmt *AssertSuccess(StmtResult R) {
298    assert(!R.isInvalid() && "operation was asserted to never fail!");
299    return R.get();
300  }
301
302} // namespace clang
303
304#endif // LLVM_CLANG_SEMA_OWNERSHIP_H
305