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