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 29 namespace clang { 30 31 class CXXBaseSpecifier; 32 class CXXCtorInitializer; 33 class Decl; 34 class Expr; 35 class ParsedTemplateArgument; 36 class QualType; 37 class Stmt; 38 class TemplateName; 39 class 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 114 115 namespace 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 132 133 namespace clang { 134 135 // Basic 136 class DiagnosticBuilder; 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. 141 template<class Ptr> 142 struct IsResultPtrLowBitFree { 143 static const bool value = false; 144 }; 145 146 /// ActionResult - This structure is used while parsing/acting on 147 /// expressions, stmts, etc. It encapsulates both the object returned by 148 /// the action, plus a sense of whether or not it is valid. 149 /// When CompressInvalid is true, the "invalid" flag will be 150 /// stored in the low bit of the Val pointer. 151 template<class PtrTy, 152 bool CompressInvalid = IsResultPtrLowBitFree<PtrTy>::value> 153 class ActionResult { 154 PtrTy Val; 155 bool Invalid; 156 157 public: 158 ActionResult(bool Invalid = false) : Val(PtrTy()), Invalid(Invalid) {} 159 ActionResult(PtrTy val) : Val(val), Invalid(false) {} 160 ActionResult(const DiagnosticBuilder &) : Val(PtrTy()), Invalid(true) {} 161 162 // These two overloads prevent void* -> bool conversions. 163 ActionResult(const void *) = delete; 164 ActionResult(volatile void *) = delete; 165 166 bool isInvalid() const { return Invalid; } 167 bool isUsable() const { return !Invalid && Val; } 168 bool isUnset() const { return !Invalid && !Val; } 169 170 PtrTy get() const { return Val; } 171 template <typename T> T *getAs() { return static_cast<T*>(get()); } 172 173 void set(PtrTy V) { Val = V; } 174 175 const ActionResult &operator=(PtrTy RHS) { 176 Val = RHS; 177 Invalid = false; 178 return *this; 179 } 180 }; 181 182 // This ActionResult partial specialization places the "invalid" 183 // flag into the low bit of the pointer. 184 template<typename PtrTy> 185 class ActionResult<PtrTy, true> { 186 // A pointer whose low bit is 1 if this result is invalid, 0 187 // otherwise. 188 uintptr_t PtrWithInvalid; 189 190 using PtrTraits = llvm::PointerLikeTypeTraits<PtrTy>; 191 192 public: 193 ActionResult(bool Invalid = false) 194 : PtrWithInvalid(static_cast<uintptr_t>(Invalid)) {} 195 196 ActionResult(PtrTy V) { 197 void *VP = PtrTraits::getAsVoidPointer(V); 198 PtrWithInvalid = reinterpret_cast<uintptr_t>(VP); 199 assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer"); 200 } 201 202 ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) {} 203 204 // These two overloads prevent void* -> bool conversions. 205 ActionResult(const void *) = delete; 206 ActionResult(volatile void *) = delete; 207 208 bool isInvalid() const { return PtrWithInvalid & 0x01; } 209 bool isUsable() const { return PtrWithInvalid > 0x01; } 210 bool isUnset() const { return PtrWithInvalid == 0; } 211 212 PtrTy get() const { 213 void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01); 214 return PtrTraits::getFromVoidPointer(VP); 215 } 216 217 template <typename T> T *getAs() { return static_cast<T*>(get()); } 218 219 void set(PtrTy V) { 220 void *VP = PtrTraits::getAsVoidPointer(V); 221 PtrWithInvalid = reinterpret_cast<uintptr_t>(VP); 222 assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer"); 223 } 224 225 const ActionResult &operator=(PtrTy RHS) { 226 void *VP = PtrTraits::getAsVoidPointer(RHS); 227 PtrWithInvalid = reinterpret_cast<uintptr_t>(VP); 228 assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer"); 229 return *this; 230 } 231 232 // For types where we can fit a flag in with the pointer, provide 233 // conversions to/from pointer type. 234 static ActionResult getFromOpaquePointer(void *P) { 235 ActionResult Result; 236 Result.PtrWithInvalid = (uintptr_t)P; 237 return Result; 238 } 239 void *getAsOpaquePointer() const { return (void*)PtrWithInvalid; } 240 }; 241 242 /// An opaque type for threading parsed type information through the 243 /// parser. 244 using ParsedType = OpaquePtr<QualType>; 245 using UnionParsedType = UnionOpaquePtr<QualType>; 246 247 // We can re-use the low bit of expression, statement, base, and 248 // member-initializer pointers for the "invalid" flag of 249 // ActionResult. 250 template<> struct IsResultPtrLowBitFree<Expr*> { 251 static const bool value = true; 252 }; 253 template<> struct IsResultPtrLowBitFree<Stmt*> { 254 static const bool value = true; 255 }; 256 template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> { 257 static const bool value = true; 258 }; 259 template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> { 260 static const bool value = true; 261 }; 262 263 using ExprResult = ActionResult<Expr *>; 264 using StmtResult = ActionResult<Stmt *>; 265 using TypeResult = ActionResult<ParsedType>; 266 using BaseResult = ActionResult<CXXBaseSpecifier *>; 267 using MemInitResult = ActionResult<CXXCtorInitializer *>; 268 269 using DeclResult = ActionResult<Decl *>; 270 using ParsedTemplateTy = OpaquePtr<TemplateName>; 271 using UnionParsedTemplateTy = UnionOpaquePtr<TemplateName>; 272 273 using MultiExprArg = MutableArrayRef<Expr *>; 274 using MultiStmtArg = MutableArrayRef<Stmt *>; 275 using ASTTemplateArgsPtr = MutableArrayRef<ParsedTemplateArgument>; 276 using MultiTypeArg = MutableArrayRef<ParsedType>; 277 using MultiTemplateParamsArg = MutableArrayRef<TemplateParameterList *>; 278 279 inline ExprResult ExprError() { return ExprResult(true); } 280 inline StmtResult StmtError() { return StmtResult(true); } 281 inline TypeResult TypeError() { return TypeResult(true); } 282 283 inline ExprResult ExprError(const DiagnosticBuilder&) { return ExprError(); } 284 inline StmtResult StmtError(const DiagnosticBuilder&) { return StmtError(); } 285 286 inline ExprResult ExprEmpty() { return ExprResult(false); } 287 inline StmtResult StmtEmpty() { return StmtResult(false); } 288 289 inline Expr *AssertSuccess(ExprResult R) { 290 assert(!R.isInvalid() && "operation was asserted to never fail!"); 291 return R.get(); 292 } 293 294 inline Stmt *AssertSuccess(StmtResult R) { 295 assert(!R.isInvalid() && "operation was asserted to never fail!"); 296 return R.get(); 297 } 298 299 } // namespace clang 300 301 #endif // LLVM_CLANG_SEMA_OWNERSHIP_H 302