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 OpaquePtr(void * Ptr)53 explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {} 54 55 using Traits = llvm::PointerLikeTypeTraits<PtrTy>; 56 57 public: 58 OpaquePtr(std::nullptr_t = nullptr) {} 59 make(PtrTy P)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*>. getPtrTo()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. getPtrAs()76 template <typename PtrT> PtrT getPtrAs() const { 77 return get(); 78 } 79 get()80 PtrTy get() const { 81 return Traits::getFromVoidPointer(Ptr); 82 } 83 set(PtrTy P)84 void set(PtrTy P) { 85 Ptr = Traits::getAsVoidPointer(P); 86 } 87 88 explicit operator bool() const { return Ptr != nullptr; } 89 getAsOpaquePtr()90 void *getAsOpaquePtr() const { return Ptr; } getFromOpaquePtr(void * P)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 makeUnionOpaquePtr99 static UnionOpaquePtr make(OpaquePtr<T> P) { 100 UnionOpaquePtr OP = { P.getAsOpaquePtr() }; 101 return OP; 102 } 103 getUnionOpaquePtr104 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 class StreamingDiagnostic; 136 137 // Determines whether the low bit of the result pointer for the 138 // given UID is always zero. If so, ActionResult will use that bit 139 // for it's "invalid" flag. 140 template <class Ptr> struct IsResultPtrLowBitFree { 141 static const bool value = false; 142 }; 143 144 /// The result of parsing/analyzing an expression, statement etc. 145 /// 146 /// It may be: 147 /// - usable: a valid pointer to the result object 148 /// - unset (null but valid): for constructs that may legitimately be absent 149 /// (for example, the condition of a for loop) 150 /// - invalid: indicating an error 151 /// (no detail is provided, usually the error has already been diagnosed) 152 template <class PtrTy, bool Compress = IsResultPtrLowBitFree<PtrTy>::value> 153 class ActionResult { 154 PtrTy Val = {}; 155 bool Invalid = false; 156 157 public: 158 ActionResult(bool Invalid = false) : Val(PtrTy()), Invalid(Invalid) {} 159 ActionResult(PtrTy Val) { *this = Val; } 160 ActionResult(const DiagnosticBuilder &) : ActionResult(/*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 isUnset() const { return !Invalid && !Val; } 168 bool isUsable() const { return !isInvalid() && !isUnset(); } 169 170 PtrTy get() const { return Val; } 171 template <typename T> T *getAs() { return static_cast<T *>(get()); } 172 173 ActionResult &operator=(PtrTy RHS) { 174 Val = RHS; 175 Invalid = false; 176 return *this; 177 } 178 }; 179 180 // If we PtrTy has a free bit, we can represent "invalid" as nullptr|1. 181 template <typename PtrTy> class ActionResult<PtrTy, true> { 182 static constexpr uintptr_t UnsetValue = 0x0; 183 static constexpr uintptr_t InvalidValue = 0x1; 184 185 uintptr_t Value = UnsetValue; 186 187 using PtrTraits = llvm::PointerLikeTypeTraits<PtrTy>; 188 189 public: 190 ActionResult(bool Invalid = false) 191 : Value(Invalid ? InvalidValue : UnsetValue) {} 192 ActionResult(PtrTy V) { *this = V; } 193 ActionResult(const DiagnosticBuilder &) : ActionResult(/*Invalid=*/true) {} 194 195 // These two overloads prevent void* -> bool conversions. 196 ActionResult(const void *) = delete; 197 ActionResult(volatile void *) = delete; 198 199 bool isInvalid() const { return Value == InvalidValue; } 200 bool isUnset() const { return Value == UnsetValue; } 201 bool isUsable() const { return !isInvalid() && !isUnset(); } 202 203 PtrTy get() const { 204 void *VP = reinterpret_cast<void *>(Value & ~0x01); 205 return PtrTraits::getFromVoidPointer(VP); 206 } 207 template <typename T> T *getAs() { return static_cast<T *>(get()); } 208 209 ActionResult &operator=(PtrTy RHS) { 210 void *VP = PtrTraits::getAsVoidPointer(RHS); 211 Value = reinterpret_cast<uintptr_t>(VP); 212 assert((Value & 0x01) == 0 && "Badly aligned pointer"); 213 return *this; 214 } 215 216 // For types where we can fit a flag in with the pointer, provide 217 // conversions to/from pointer type. 218 static ActionResult getFromOpaquePointer(void *P) { 219 ActionResult Result; 220 Result.Value = (uintptr_t)P; 221 assert(Result.isInvalid() || 222 PtrTraits::getAsVoidPointer(Result.get()) == P); 223 return Result; 224 } 225 void *getAsOpaquePointer() const { return (void *)Value; } 226 }; 227 228 /// An opaque type for threading parsed type information through the parser. 229 using ParsedType = OpaquePtr<QualType>; 230 using UnionParsedType = UnionOpaquePtr<QualType>; 231 232 // We can re-use the low bit of expression, statement, base, and 233 // member-initializer pointers for the "invalid" flag of 234 // ActionResult. 235 template <> struct IsResultPtrLowBitFree<Expr *> { 236 static const bool value = true; 237 }; 238 template <> struct IsResultPtrLowBitFree<Stmt *> { 239 static const bool value = true; 240 }; 241 template <> struct IsResultPtrLowBitFree<CXXBaseSpecifier *> { 242 static const bool value = true; 243 }; 244 template <> struct IsResultPtrLowBitFree<CXXCtorInitializer *> { 245 static const bool value = true; 246 }; 247 248 using ExprResult = ActionResult<Expr *>; 249 using StmtResult = ActionResult<Stmt *>; 250 using TypeResult = ActionResult<ParsedType>; 251 using BaseResult = ActionResult<CXXBaseSpecifier *>; 252 using MemInitResult = ActionResult<CXXCtorInitializer *>; 253 254 using DeclResult = ActionResult<Decl *>; 255 using ParsedTemplateTy = OpaquePtr<TemplateName>; 256 using UnionParsedTemplateTy = UnionOpaquePtr<TemplateName>; 257 258 using MultiExprArg = MutableArrayRef<Expr *>; 259 using MultiStmtArg = MutableArrayRef<Stmt *>; 260 using ASTTemplateArgsPtr = MutableArrayRef<ParsedTemplateArgument>; 261 using MultiTypeArg = MutableArrayRef<ParsedType>; 262 using MultiTemplateParamsArg = MutableArrayRef<TemplateParameterList *>; 263 264 inline ExprResult ExprError() { return ExprResult(true); } 265 inline StmtResult StmtError() { return StmtResult(true); } 266 inline TypeResult TypeError() { return TypeResult(true); } 267 268 inline ExprResult ExprError(const StreamingDiagnostic &) { return ExprError(); } 269 inline StmtResult StmtError(const StreamingDiagnostic &) { return StmtError(); } 270 271 inline ExprResult ExprEmpty() { return ExprResult(false); } 272 inline StmtResult StmtEmpty() { return StmtResult(false); } 273 274 inline Expr *AssertSuccess(ExprResult R) { 275 assert(!R.isInvalid() && "operation was asserted to never fail!"); 276 return R.get(); 277 } 278 279 inline Stmt *AssertSuccess(StmtResult R) { 280 assert(!R.isInvalid() && "operation was asserted to never fail!"); 281 return R.get(); 282 } 283 284 } // namespace clang 285 286 #endif // LLVM_CLANG_SEMA_OWNERSHIP_H 287