270 lines · cpp
1//===----------------------------------------------------------------------===//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-exception6//7//===----------------------------------------------------------------------===//8 9#include "VirtualNearMissCheck.h"10#include "clang/AST/ASTContext.h"11#include "clang/AST/CXXInheritance.h"12#include "clang/ASTMatchers/ASTMatchFinder.h"13#include "clang/Lex/Lexer.h"14 15using namespace clang::ast_matchers;16 17namespace clang::tidy::bugprone {18 19namespace {20AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }21 22AST_MATCHER(CXXMethodDecl, isOverloadedOperator) {23 return Node.isOverloadedOperator();24}25} // namespace26 27/// Finds out if the given method overrides some method.28static bool isOverrideMethod(const CXXMethodDecl *MD) {29 return MD->size_overridden_methods() > 0 || MD->hasAttr<OverrideAttr>();30}31 32/// Checks whether the return types are covariant, according to33/// C++[class.virtual]p7.34///35/// Similar with clang::Sema::CheckOverridingFunctionReturnType.36/// \returns true if the return types of BaseMD and DerivedMD are covariant.37static bool checkOverridingFunctionReturnType(const ASTContext *Context,38 const CXXMethodDecl *BaseMD,39 const CXXMethodDecl *DerivedMD) {40 const QualType BaseReturnTy = BaseMD->getType()41 ->castAs<FunctionType>()42 ->getReturnType()43 .getCanonicalType();44 const QualType DerivedReturnTy = DerivedMD->getType()45 ->castAs<FunctionType>()46 ->getReturnType()47 .getCanonicalType();48 49 if (DerivedReturnTy->isDependentType() || BaseReturnTy->isDependentType())50 return false;51 52 // Check if return types are identical.53 if (ASTContext::hasSameType(DerivedReturnTy, BaseReturnTy))54 return true;55 56 /// Check if the return types are covariant.57 58 // Both types must be pointers or references to classes.59 if (!(BaseReturnTy->isPointerType() && DerivedReturnTy->isPointerType()) &&60 !(BaseReturnTy->isReferenceType() && DerivedReturnTy->isReferenceType()))61 return false;62 63 /// BTy is the class type in return type of BaseMD. For example,64 /// B* Base::md()65 /// While BRD is the declaration of B.66 const QualType DTy = DerivedReturnTy->getPointeeType().getCanonicalType();67 const QualType BTy = BaseReturnTy->getPointeeType().getCanonicalType();68 69 const CXXRecordDecl *DRD = DTy->getAsCXXRecordDecl();70 const CXXRecordDecl *BRD = BTy->getAsCXXRecordDecl();71 if (DRD == nullptr || BRD == nullptr)72 return false;73 74 if (!DRD->hasDefinition() || !BRD->hasDefinition())75 return false;76 77 if (DRD == BRD)78 return true;79 80 if (!ASTContext::hasSameUnqualifiedType(DTy, BTy)) {81 // Begin checking whether the conversion from D to B is valid.82 CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,83 /*DetectVirtual=*/false);84 85 // Check whether D is derived from B, and fill in a CXXBasePaths object.86 if (!DRD->isDerivedFrom(BRD, Paths))87 return false;88 89 // Check ambiguity.90 if (Paths.isAmbiguous(91 ASTContext::getCanonicalType(BTy).getUnqualifiedType()))92 return false;93 94 // Check accessibility.95 // FIXME: We currently only support checking if B is accessible base class96 // of D, or D is the same class which DerivedMD is in.97 const bool IsItself =98 DRD->getCanonicalDecl() == DerivedMD->getParent()->getCanonicalDecl();99 bool HasPublicAccess = false;100 for (const auto &Path : Paths) {101 if (Path.Access == AS_public)102 HasPublicAccess = true;103 }104 if (!HasPublicAccess && !IsItself)105 return false;106 // End checking conversion from D to B.107 }108 109 // Both pointers or references should have the same cv-qualification.110 if (DerivedReturnTy.getLocalCVRQualifiers() !=111 BaseReturnTy.getLocalCVRQualifiers())112 return false;113 114 // The class type D should have the same cv-qualification as or less115 // cv-qualification than the class type B.116 if (DTy.isMoreQualifiedThan(BTy, *Context))117 return false;118 119 return true;120}121 122/// \returns decayed type for arrays and functions.123static QualType getDecayedType(QualType Type) {124 if (const auto *Decayed = Type->getAs<DecayedType>())125 return Decayed->getDecayedType();126 return Type;127}128 129/// \returns true if the param types are the same.130static bool checkParamTypes(const CXXMethodDecl *BaseMD,131 const CXXMethodDecl *DerivedMD) {132 const unsigned NumParamA = BaseMD->getNumParams();133 const unsigned NumParamB = DerivedMD->getNumParams();134 if (NumParamA != NumParamB)135 return false;136 137 for (unsigned I = 0; I < NumParamA; I++) {138 if (getDecayedType(BaseMD->getParamDecl(I)->getType().getCanonicalType()) !=139 getDecayedType(140 DerivedMD->getParamDecl(I)->getType().getCanonicalType()))141 return false;142 }143 return true;144}145 146/// \returns true if derived method can override base method except for the147/// name.148static bool checkOverrideWithoutName(const ASTContext *Context,149 const CXXMethodDecl *BaseMD,150 const CXXMethodDecl *DerivedMD) {151 if (BaseMD->isStatic() != DerivedMD->isStatic())152 return false;153 154 if (BaseMD->getType() == DerivedMD->getType())155 return true;156 157 // Now the function types are not identical. Then check if the return types158 // are covariant and if the param types are the same.159 if (!checkOverridingFunctionReturnType(Context, BaseMD, DerivedMD))160 return false;161 return checkParamTypes(BaseMD, DerivedMD);162}163 164/// Check whether BaseMD overrides DerivedMD.165///166/// Prerequisite: the class which BaseMD is in should be a base class of that167/// DerivedMD is in.168static bool checkOverrideByDerivedMethod(const CXXMethodDecl *BaseMD,169 const CXXMethodDecl *DerivedMD) {170 for (CXXMethodDecl::method_iterator I = DerivedMD->begin_overridden_methods(),171 E = DerivedMD->end_overridden_methods();172 I != E; ++I) {173 const CXXMethodDecl *OverriddenMD = *I;174 if (BaseMD->getCanonicalDecl() == OverriddenMD->getCanonicalDecl())175 return true;176 }177 178 return false;179}180 181bool VirtualNearMissCheck::isPossibleToBeOverridden(182 const CXXMethodDecl *BaseMD) {183 auto [Iter, Inserted] = PossibleMap.try_emplace(BaseMD);184 if (!Inserted)185 return Iter->second;186 187 const bool IsPossible =188 !BaseMD->isImplicit() && !isa<CXXConstructorDecl>(BaseMD) &&189 !isa<CXXDestructorDecl>(BaseMD) && BaseMD->isVirtual() &&190 !BaseMD->isOverloadedOperator() && !isa<CXXConversionDecl>(BaseMD);191 Iter->second = IsPossible;192 return IsPossible;193}194 195bool VirtualNearMissCheck::isOverriddenByDerivedClass(196 const CXXMethodDecl *BaseMD, const CXXRecordDecl *DerivedRD) {197 auto Key = std::make_pair(BaseMD, DerivedRD);198 auto Iter = OverriddenMap.find(Key);199 if (Iter != OverriddenMap.end())200 return Iter->second;201 202 bool IsOverridden = false;203 for (const CXXMethodDecl *DerivedMD : DerivedRD->methods()) {204 if (!isOverrideMethod(DerivedMD))205 continue;206 207 if (checkOverrideByDerivedMethod(BaseMD, DerivedMD)) {208 IsOverridden = true;209 break;210 }211 }212 OverriddenMap[Key] = IsOverridden;213 return IsOverridden;214}215 216void VirtualNearMissCheck::registerMatchers(MatchFinder *Finder) {217 Finder->addMatcher(218 cxxMethodDecl(219 unless(anyOf(isOverride(), isImplicit(), cxxConstructorDecl(),220 cxxDestructorDecl(), cxxConversionDecl(), isStatic(),221 isOverloadedOperator())))222 .bind("method"),223 this);224}225 226void VirtualNearMissCheck::check(const MatchFinder::MatchResult &Result) {227 const auto *DerivedMD = Result.Nodes.getNodeAs<CXXMethodDecl>("method");228 assert(DerivedMD);229 230 const ASTContext *Context = Result.Context;231 232 const auto *DerivedRD = DerivedMD->getParent()->getDefinition();233 assert(DerivedRD);234 235 for (const auto &BaseSpec : DerivedRD->bases()) {236 if (const auto *BaseRD = BaseSpec.getType()->getAsCXXRecordDecl()) {237 for (const auto *BaseMD : BaseRD->methods()) {238 if (!isPossibleToBeOverridden(BaseMD))239 continue;240 241 if (isOverriddenByDerivedClass(BaseMD, DerivedRD))242 continue;243 244 const unsigned EditDistance = BaseMD->getName().edit_distance(245 DerivedMD->getName(), EditDistanceThreshold);246 if (EditDistance > 0 && EditDistance <= EditDistanceThreshold) {247 if (checkOverrideWithoutName(Context, BaseMD, DerivedMD)) {248 // A "virtual near miss" is found.249 auto Range = CharSourceRange::getTokenRange(250 SourceRange(DerivedMD->getLocation()));251 252 const bool ApplyFix = !BaseMD->isTemplateInstantiation() &&253 !DerivedMD->isTemplateInstantiation();254 auto Diag =255 diag(DerivedMD->getBeginLoc(),256 "method '%0' has a similar name and the same signature as "257 "virtual method '%1'; did you mean to override it?")258 << DerivedMD->getQualifiedNameAsString()259 << BaseMD->getQualifiedNameAsString();260 if (ApplyFix)261 Diag << FixItHint::CreateReplacement(Range, BaseMD->getName());262 }263 }264 }265 }266 }267}268 269} // namespace clang::tidy::bugprone270