| File: | build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp |
| Warning: | line 158, column 9 Value stored to 'ThrownType' is never read |
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| 1 | //===--- ExceptionAnalyzer.cpp - clang-tidy -------------------------------===// |
| 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 | #include "ExceptionAnalyzer.h" |
| 10 | |
| 11 | namespace clang { |
| 12 | namespace tidy { |
| 13 | namespace utils { |
| 14 | |
| 15 | void ExceptionAnalyzer::ExceptionInfo::registerException( |
| 16 | const Type *ExceptionType) { |
| 17 | assert(ExceptionType != nullptr && "Only valid types are accepted")(static_cast <bool> (ExceptionType != nullptr && "Only valid types are accepted") ? void (0) : __assert_fail ( "ExceptionType != nullptr && \"Only valid types are accepted\"" , "clang-tools-extra/clang-tidy/utils/ExceptionAnalyzer.cpp", 17, __extension__ __PRETTY_FUNCTION__)); |
| 18 | Behaviour = State::Throwing; |
| 19 | ThrownExceptions.insert(ExceptionType); |
| 20 | } |
| 21 | |
| 22 | void ExceptionAnalyzer::ExceptionInfo::registerExceptions( |
| 23 | const Throwables &Exceptions) { |
| 24 | if (Exceptions.size() == 0) |
| 25 | return; |
| 26 | Behaviour = State::Throwing; |
| 27 | ThrownExceptions.insert(Exceptions.begin(), Exceptions.end()); |
| 28 | } |
| 29 | |
| 30 | ExceptionAnalyzer::ExceptionInfo &ExceptionAnalyzer::ExceptionInfo::merge( |
| 31 | const ExceptionAnalyzer::ExceptionInfo &Other) { |
| 32 | // Only the following two cases require an update to the local |
| 33 | // 'Behaviour'. If the local entity is already throwing there will be no |
| 34 | // change and if the other entity is throwing the merged entity will throw |
| 35 | // as well. |
| 36 | // If one of both entities is 'Unknown' and the other one does not throw |
| 37 | // the merged entity is 'Unknown' as well. |
| 38 | if (Other.Behaviour == State::Throwing) |
| 39 | Behaviour = State::Throwing; |
| 40 | else if (Other.Behaviour == State::Unknown && Behaviour == State::NotThrowing) |
| 41 | Behaviour = State::Unknown; |
| 42 | |
| 43 | ContainsUnknown = ContainsUnknown || Other.ContainsUnknown; |
| 44 | ThrownExceptions.insert(Other.ThrownExceptions.begin(), |
| 45 | Other.ThrownExceptions.end()); |
| 46 | return *this; |
| 47 | } |
| 48 | |
| 49 | static bool isBaseOf(const Type *DerivedType, const Type *BaseType) { |
| 50 | const auto *DerivedClass = DerivedType->getAsCXXRecordDecl(); |
| 51 | const auto *BaseClass = BaseType->getAsCXXRecordDecl(); |
| 52 | if (!DerivedClass || !BaseClass) |
| 53 | return false; |
| 54 | |
| 55 | return !DerivedClass->forallBases( |
| 56 | [BaseClass](const CXXRecordDecl *Cur) { return Cur != BaseClass; }); |
| 57 | } |
| 58 | |
| 59 | bool ExceptionAnalyzer::ExceptionInfo::filterByCatch(const Type *BaseClass) { |
| 60 | llvm::SmallVector<const Type *, 8> TypesToDelete; |
| 61 | for (const Type *T : ThrownExceptions) { |
| 62 | if (T == BaseClass || isBaseOf(T, BaseClass)) |
| 63 | TypesToDelete.push_back(T); |
| 64 | } |
| 65 | |
| 66 | for (const Type *T : TypesToDelete) |
| 67 | ThrownExceptions.erase(T); |
| 68 | |
| 69 | reevaluateBehaviour(); |
| 70 | return TypesToDelete.size() > 0; |
| 71 | } |
| 72 | |
| 73 | ExceptionAnalyzer::ExceptionInfo & |
| 74 | ExceptionAnalyzer::ExceptionInfo::filterIgnoredExceptions( |
| 75 | const llvm::StringSet<> &IgnoredTypes, bool IgnoreBadAlloc) { |
| 76 | llvm::SmallVector<const Type *, 8> TypesToDelete; |
| 77 | // Note: Using a 'SmallSet' with 'llvm::remove_if()' is not possible. |
| 78 | // Therefore this slightly hacky implementation is required. |
| 79 | for (const Type *T : ThrownExceptions) { |
| 80 | if (const auto *TD = T->getAsTagDecl()) { |
| 81 | if (TD->getDeclName().isIdentifier()) { |
| 82 | if ((IgnoreBadAlloc && |
| 83 | (TD->getName() == "bad_alloc" && TD->isInStdNamespace())) || |
| 84 | (IgnoredTypes.count(TD->getName()) > 0)) |
| 85 | TypesToDelete.push_back(T); |
| 86 | } |
| 87 | } |
| 88 | } |
| 89 | for (const Type *T : TypesToDelete) |
| 90 | ThrownExceptions.erase(T); |
| 91 | |
| 92 | reevaluateBehaviour(); |
| 93 | return *this; |
| 94 | } |
| 95 | |
| 96 | void ExceptionAnalyzer::ExceptionInfo::clear() { |
| 97 | Behaviour = State::NotThrowing; |
| 98 | ContainsUnknown = false; |
| 99 | ThrownExceptions.clear(); |
| 100 | } |
| 101 | |
| 102 | void ExceptionAnalyzer::ExceptionInfo::reevaluateBehaviour() { |
| 103 | if (ThrownExceptions.size() == 0) |
| 104 | if (ContainsUnknown) |
| 105 | Behaviour = State::Unknown; |
| 106 | else |
| 107 | Behaviour = State::NotThrowing; |
| 108 | else |
| 109 | Behaviour = State::Throwing; |
| 110 | } |
| 111 | |
| 112 | ExceptionAnalyzer::ExceptionInfo ExceptionAnalyzer::throwsException( |
| 113 | const FunctionDecl *Func, |
| 114 | llvm::SmallSet<const FunctionDecl *, 32> &CallStack) { |
| 115 | if (CallStack.count(Func)) |
| 116 | return ExceptionInfo::createNonThrowing(); |
| 117 | |
| 118 | if (const Stmt *Body = Func->getBody()) { |
| 119 | CallStack.insert(Func); |
| 120 | ExceptionInfo Result = |
| 121 | throwsException(Body, ExceptionInfo::Throwables(), CallStack); |
| 122 | |
| 123 | // For a constructor, we also have to check the initializers. |
| 124 | if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(Func)) { |
| 125 | for (const CXXCtorInitializer *Init : Ctor->inits()) { |
| 126 | ExceptionInfo Excs = throwsException( |
| 127 | Init->getInit(), ExceptionInfo::Throwables(), CallStack); |
| 128 | Result.merge(Excs); |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | CallStack.erase(Func); |
| 133 | return Result; |
| 134 | } |
| 135 | |
| 136 | auto Result = ExceptionInfo::createUnknown(); |
| 137 | if (const auto *FPT = Func->getType()->getAs<FunctionProtoType>()) { |
| 138 | for (const QualType &Ex : FPT->exceptions()) |
| 139 | Result.registerException(Ex.getTypePtr()); |
| 140 | } |
| 141 | return Result; |
| 142 | } |
| 143 | |
| 144 | /// Analyzes a single statement on it's throwing behaviour. This is in principle |
| 145 | /// possible except some 'Unknown' functions are called. |
| 146 | ExceptionAnalyzer::ExceptionInfo ExceptionAnalyzer::throwsException( |
| 147 | const Stmt *St, const ExceptionInfo::Throwables &Caught, |
| 148 | llvm::SmallSet<const FunctionDecl *, 32> &CallStack) { |
| 149 | auto Results = ExceptionInfo::createNonThrowing(); |
| 150 | if (!St) |
| 151 | return Results; |
| 152 | |
| 153 | if (const auto *Throw = dyn_cast<CXXThrowExpr>(St)) { |
| 154 | if (const auto *ThrownExpr = Throw->getSubExpr()) { |
| 155 | const auto *ThrownType = |
| 156 | ThrownExpr->getType()->getUnqualifiedDesugaredType(); |
| 157 | if (ThrownType->isReferenceType()) |
| 158 | ThrownType = ThrownType->castAs<ReferenceType>() |
Value stored to 'ThrownType' is never read | |
| 159 | ->getPointeeType() |
| 160 | ->getUnqualifiedDesugaredType(); |
| 161 | Results.registerException( |
| 162 | ThrownExpr->getType()->getUnqualifiedDesugaredType()); |
| 163 | } else |
| 164 | // A rethrow of a caught exception happens which makes it possible |
| 165 | // to throw all exception that are caught in the 'catch' clause of |
| 166 | // the parent try-catch block. |
| 167 | Results.registerExceptions(Caught); |
| 168 | } else if (const auto *Try = dyn_cast<CXXTryStmt>(St)) { |
| 169 | ExceptionInfo Uncaught = |
| 170 | throwsException(Try->getTryBlock(), Caught, CallStack); |
| 171 | for (unsigned I = 0; I < Try->getNumHandlers(); ++I) { |
| 172 | const CXXCatchStmt *Catch = Try->getHandler(I); |
| 173 | |
| 174 | // Everything is catched through 'catch(...)'. |
| 175 | if (!Catch->getExceptionDecl()) { |
| 176 | ExceptionInfo Rethrown = throwsException( |
| 177 | Catch->getHandlerBlock(), Uncaught.getExceptionTypes(), CallStack); |
| 178 | Results.merge(Rethrown); |
| 179 | Uncaught.clear(); |
| 180 | } else { |
| 181 | const auto *CaughtType = |
| 182 | Catch->getCaughtType()->getUnqualifiedDesugaredType(); |
| 183 | if (CaughtType->isReferenceType()) { |
| 184 | CaughtType = CaughtType->castAs<ReferenceType>() |
| 185 | ->getPointeeType() |
| 186 | ->getUnqualifiedDesugaredType(); |
| 187 | } |
| 188 | |
| 189 | // If the caught exception will catch multiple previously potential |
| 190 | // thrown types (because it's sensitive to inheritance) the throwing |
| 191 | // situation changes. First of all filter the exception types and |
| 192 | // analyze if the baseclass-exception is rethrown. |
| 193 | if (Uncaught.filterByCatch(CaughtType)) { |
| 194 | ExceptionInfo::Throwables CaughtExceptions; |
| 195 | CaughtExceptions.insert(CaughtType); |
| 196 | ExceptionInfo Rethrown = throwsException(Catch->getHandlerBlock(), |
| 197 | CaughtExceptions, CallStack); |
| 198 | Results.merge(Rethrown); |
| 199 | } |
| 200 | } |
| 201 | } |
| 202 | Results.merge(Uncaught); |
| 203 | } else if (const auto *Call = dyn_cast<CallExpr>(St)) { |
| 204 | if (const FunctionDecl *Func = Call->getDirectCallee()) { |
| 205 | ExceptionInfo Excs = throwsException(Func, CallStack); |
| 206 | Results.merge(Excs); |
| 207 | } |
| 208 | } else if (const auto *Construct = dyn_cast<CXXConstructExpr>(St)) { |
| 209 | ExceptionInfo Excs = |
| 210 | throwsException(Construct->getConstructor(), CallStack); |
| 211 | Results.merge(Excs); |
| 212 | } else if (const auto *DefaultInit = dyn_cast<CXXDefaultInitExpr>(St)) { |
| 213 | ExceptionInfo Excs = |
| 214 | throwsException(DefaultInit->getExpr(), Caught, CallStack); |
| 215 | Results.merge(Excs); |
| 216 | } else { |
| 217 | for (const Stmt *Child : St->children()) { |
| 218 | ExceptionInfo Excs = throwsException(Child, Caught, CallStack); |
| 219 | Results.merge(Excs); |
| 220 | } |
| 221 | } |
| 222 | return Results; |
| 223 | } |
| 224 | |
| 225 | ExceptionAnalyzer::ExceptionInfo |
| 226 | ExceptionAnalyzer::analyzeImpl(const FunctionDecl *Func) { |
| 227 | ExceptionInfo ExceptionList; |
| 228 | |
| 229 | // Check if the function has already been analyzed and reuse that result. |
| 230 | if (FunctionCache.count(Func) == 0) { |
| 231 | llvm::SmallSet<const FunctionDecl *, 32> CallStack; |
| 232 | ExceptionList = throwsException(Func, CallStack); |
| 233 | |
| 234 | // Cache the result of the analysis. This is done prior to filtering |
| 235 | // because it is best to keep as much information as possible. |
| 236 | // The results here might be relevant to different analysis passes |
| 237 | // with different needs as well. |
| 238 | FunctionCache.insert(std::make_pair(Func, ExceptionList)); |
| 239 | } else |
| 240 | ExceptionList = FunctionCache[Func]; |
| 241 | |
| 242 | return ExceptionList; |
| 243 | } |
| 244 | |
| 245 | ExceptionAnalyzer::ExceptionInfo |
| 246 | ExceptionAnalyzer::analyzeImpl(const Stmt *Stmt) { |
| 247 | llvm::SmallSet<const FunctionDecl *, 32> CallStack; |
| 248 | return throwsException(Stmt, ExceptionInfo::Throwables(), CallStack); |
| 249 | } |
| 250 | |
| 251 | template <typename T> |
| 252 | ExceptionAnalyzer::ExceptionInfo |
| 253 | ExceptionAnalyzer::analyzeDispatch(const T *Node) { |
| 254 | ExceptionInfo ExceptionList = analyzeImpl(Node); |
| 255 | |
| 256 | if (ExceptionList.getBehaviour() == State::NotThrowing || |
| 257 | ExceptionList.getBehaviour() == State::Unknown) |
| 258 | return ExceptionList; |
| 259 | |
| 260 | // Remove all ignored exceptions from the list of exceptions that can be |
| 261 | // thrown. |
| 262 | ExceptionList.filterIgnoredExceptions(IgnoredExceptions, IgnoreBadAlloc); |
| 263 | |
| 264 | return ExceptionList; |
| 265 | } |
| 266 | |
| 267 | ExceptionAnalyzer::ExceptionInfo |
| 268 | ExceptionAnalyzer::analyze(const FunctionDecl *Func) { |
| 269 | return analyzeDispatch(Func); |
| 270 | } |
| 271 | |
| 272 | ExceptionAnalyzer::ExceptionInfo |
| 273 | ExceptionAnalyzer::analyze(const Stmt *Stmt) { |
| 274 | return analyzeDispatch(Stmt); |
| 275 | } |
| 276 | |
| 277 | } // namespace utils |
| 278 | } // namespace tidy |
| 279 | |
| 280 | } // namespace clang |