clang-tidy/bugprone/VirtualNearMissCheck.cpp - toolchain/clang-tools-extra - Git at Google

 //===--- VirtualNearMissCheck.cpp - clang-tidy-----------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #include "VirtualNearMissCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/CXXInheritance.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"

 using namespace clang::ast_matchers;

 namespace clang {
 namespace tidy {
 namespace bugprone {

 namespace {
 AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }

 AST_MATCHER(CXXMethodDecl, isOverloadedOperator) {
   return Node.isOverloadedOperator();
 }
 } // namespace

 /// Finds out if the given method overrides some method.
 static bool isOverrideMethod(const CXXMethodDecl *MD) {
   return MD->size_overridden_methods() > 0 || MD->hasAttr<OverrideAttr>();
 }

 /// Checks whether the return types are covariant, according to
 /// C++[class.virtual]p7.
 ///
 /// Similar with clang::Sema::CheckOverridingFunctionReturnType.
 /// \returns true if the return types of BaseMD and DerivedMD are covariant.
 static bool checkOverridingFunctionReturnType(const ASTContext *Context,
                                               const CXXMethodDecl *BaseMD,
                                               const CXXMethodDecl *DerivedMD) {
   QualType BaseReturnTy = BaseMD->getType()
                               ->getAs<FunctionType>()
                               ->getReturnType()
                               .getCanonicalType();
   QualType DerivedReturnTy = DerivedMD->getType()
                                  ->getAs<FunctionType>()
                                  ->getReturnType()
                                  .getCanonicalType();

   if (DerivedReturnTy->isDependentType() || BaseReturnTy->isDependentType())
     return false;

   // Check if return types are identical.
   if (Context->hasSameType(DerivedReturnTy, BaseReturnTy))
     return true;

   /// Check if the return types are covariant.

   // Both types must be pointers or references to classes.
   if (!(BaseReturnTy->isPointerType() && DerivedReturnTy->isPointerType()) &&
       !(BaseReturnTy->isReferenceType() && DerivedReturnTy->isReferenceType()))
     return false;

   /// BTy is the class type in return type of BaseMD. For example,
   ///    B* Base::md()
   /// While BRD is the declaration of B.
   QualType DTy = DerivedReturnTy->getPointeeType().getCanonicalType();
   QualType BTy = BaseReturnTy->getPointeeType().getCanonicalType();

   const CXXRecordDecl *DRD = DTy->getAsCXXRecordDecl();
   const CXXRecordDecl *BRD = BTy->getAsCXXRecordDecl();
   if (DRD == nullptr || BRD == nullptr)
     return false;

   if (!DRD->hasDefinition() || !BRD->hasDefinition())
     return false;

   if (DRD == BRD)
     return true;

   if (!Context->hasSameUnqualifiedType(DTy, BTy)) {
     // Begin checking whether the conversion from D to B is valid.
     CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
                        /*DetectVirtual=*/false);

     // Check whether D is derived from B, and fill in a CXXBasePaths object.
     if (!DRD->isDerivedFrom(BRD, Paths))
       return false;

     // Check ambiguity.
     if (Paths.isAmbiguous(Context->getCanonicalType(BTy).getUnqualifiedType()))
       return false;

     // Check accessibility.
     // FIXME: We currently only support checking if B is accessible base class
     // of D, or D is the same class which DerivedMD is in.
     bool IsItself =
         DRD->getCanonicalDecl() == DerivedMD->getParent()->getCanonicalDecl();
     bool HasPublicAccess = false;
     for (const auto &Path : Paths) {
       if (Path.Access == AS_public)
         HasPublicAccess = true;
     }
     if (!HasPublicAccess && !IsItself)
       return false;
     // End checking conversion from D to B.
   }

   // Both pointers or references should have the same cv-qualification.
   if (DerivedReturnTy.getLocalCVRQualifiers() !=
       BaseReturnTy.getLocalCVRQualifiers())
     return false;

   // The class type D should have the same cv-qualification as or less
   // cv-qualification than the class type B.
   if (DTy.isMoreQualifiedThan(BTy))
     return false;

   return true;
 }

 /// \returns decayed type for arrays and functions.
 static QualType getDecayedType(QualType Type) {
   if (const auto *Decayed = Type->getAs<DecayedType>())
     return Decayed->getDecayedType();
   return Type;
 }

 /// \returns true if the param types are the same.
 static bool checkParamTypes(const CXXMethodDecl *BaseMD,
                             const CXXMethodDecl *DerivedMD) {
   unsigned NumParamA = BaseMD->getNumParams();
   unsigned NumParamB = DerivedMD->getNumParams();
   if (NumParamA != NumParamB)
     return false;

   for (unsigned I = 0; I < NumParamA; I++) {
     if (getDecayedType(BaseMD->getParamDecl(I)->getType().getCanonicalType()) !=
         getDecayedType(
             DerivedMD->getParamDecl(I)->getType().getCanonicalType()))
       return false;
   }
   return true;
 }

 /// \returns true if derived method can override base method except for the
 /// name.
 static bool checkOverrideWithoutName(const ASTContext *Context,
                                      const CXXMethodDecl *BaseMD,
                                      const CXXMethodDecl *DerivedMD) {
   if (BaseMD->isStatic() != DerivedMD->isStatic())
     return false;

   if (BaseMD->getType() == DerivedMD->getType())
     return true;

   // Now the function types are not identical. Then check if the return types
   // are covariant and if the param types are the same.
   if (!checkOverridingFunctionReturnType(Context, BaseMD, DerivedMD))
     return false;
   return checkParamTypes(BaseMD, DerivedMD);
 }

 /// Check whether BaseMD overrides DerivedMD.
 ///
 /// Prerequisite: the class which BaseMD is in should be a base class of that
 /// DerivedMD is in.
 static bool checkOverrideByDerivedMethod(const CXXMethodDecl *BaseMD,
                                          const CXXMethodDecl *DerivedMD) {
   for (CXXMethodDecl::method_iterator I = DerivedMD->begin_overridden_methods(),
                                       E = DerivedMD->end_overridden_methods();
        I != E; ++I) {
     const CXXMethodDecl *OverriddenMD = *I;
     if (BaseMD->getCanonicalDecl() == OverriddenMD->getCanonicalDecl())
       return true;
   }

   return false;
 }

 bool VirtualNearMissCheck::isPossibleToBeOverridden(
     const CXXMethodDecl *BaseMD) {
   auto Iter = PossibleMap.find(BaseMD);
   if (Iter != PossibleMap.end())
     return Iter->second;

   bool IsPossible = !BaseMD->isImplicit() && !isa<CXXConstructorDecl>(BaseMD) &&
                     !isa<CXXDestructorDecl>(BaseMD) && BaseMD->isVirtual() &&
                     !BaseMD->isOverloadedOperator() &&
                     !isa<CXXConversionDecl>(BaseMD);
   PossibleMap[BaseMD] = IsPossible;
   return IsPossible;
 }

 bool VirtualNearMissCheck::isOverriddenByDerivedClass(
     const CXXMethodDecl *BaseMD, const CXXRecordDecl *DerivedRD) {
   auto Key = std::make_pair(BaseMD, DerivedRD);
   auto Iter = OverriddenMap.find(Key);
   if (Iter != OverriddenMap.end())
     return Iter->second;

   bool IsOverridden = false;
   for (const CXXMethodDecl *DerivedMD : DerivedRD->methods()) {
     if (!isOverrideMethod(DerivedMD))
       continue;

     if (checkOverrideByDerivedMethod(BaseMD, DerivedMD)) {
       IsOverridden = true;
       break;
     }
   }
   OverriddenMap[Key] = IsOverridden;
   return IsOverridden;
 }

 void VirtualNearMissCheck::registerMatchers(MatchFinder *Finder) {
   if (!getLangOpts().CPlusPlus)
     return;

   Finder->addMatcher(
       cxxMethodDecl(
           unless(anyOf(isOverride(), isImplicit(), cxxConstructorDecl(),
                        cxxDestructorDecl(), cxxConversionDecl(), isStatic(),
                        isOverloadedOperator())))
           .bind("method"),
       this);
 }

 void VirtualNearMissCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *DerivedMD = Result.Nodes.getNodeAs<CXXMethodDecl>("method");
   assert(DerivedMD);

   const ASTContext *Context = Result.Context;

   const auto *DerivedRD = DerivedMD->getParent()->getDefinition();
   assert(DerivedRD);

   for (const auto &BaseSpec : DerivedRD->bases()) {
     if (const auto *BaseRD = BaseSpec.getType()->getAsCXXRecordDecl()) {
       for (const auto *BaseMD : BaseRD->methods()) {
         if (!isPossibleToBeOverridden(BaseMD))
           continue;

         if (isOverriddenByDerivedClass(BaseMD, DerivedRD))
           continue;

         unsigned EditDistance = BaseMD->getName().edit_distance(
             DerivedMD->getName(), EditDistanceThreshold);
         if (EditDistance > 0 && EditDistance <= EditDistanceThreshold) {
           if (checkOverrideWithoutName(Context, BaseMD, DerivedMD)) {
             // A "virtual near miss" is found.
             auto Range = CharSourceRange::getTokenRange(
                 SourceRange(DerivedMD->getLocation()));

             bool ApplyFix = !BaseMD->isTemplateInstantiation() &&
                             !DerivedMD->isTemplateInstantiation();
             auto Diag =
                 diag(DerivedMD->getBeginLoc(),
                      "method '%0' has a similar name and the same signature as "
                      "virtual method '%1'; did you mean to override it?")
                 << DerivedMD->getQualifiedNameAsString()
                 << BaseMD->getQualifiedNameAsString();
             if (ApplyFix)
               Diag << FixItHint::CreateReplacement(Range, BaseMD->getName());
           }
         }
       }
     }
   }
 }

 } // namespace bugprone
 } // namespace tidy
 } // namespace clang
	//===--- VirtualNearMissCheck.cpp - clang-tidy-----------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#include "VirtualNearMissCheck.h"
	#include "clang/AST/ASTContext.h"
	#include "clang/AST/CXXInheritance.h"
	#include "clang/ASTMatchers/ASTMatchFinder.h"
	#include "clang/Lex/Lexer.h"

	using namespace clang::ast_matchers;

	namespace clang {
	namespace tidy {
	namespace bugprone {

	namespace {
	AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }

	AST_MATCHER(CXXMethodDecl, isOverloadedOperator) {
	return Node.isOverloadedOperator();
	}
	} // namespace

	/// Finds out if the given method overrides some method.
	static bool isOverrideMethod(const CXXMethodDecl *MD) {
	return MD->size_overridden_methods() > 0 \|\| MD->hasAttr<OverrideAttr>();
	}

	/// Checks whether the return types are covariant, according to
	/// C++[class.virtual]p7.
	///
	/// Similar with clang::Sema::CheckOverridingFunctionReturnType.
	/// \returns true if the return types of BaseMD and DerivedMD are covariant.
	static bool checkOverridingFunctionReturnType(const ASTContext *Context,
	const CXXMethodDecl *BaseMD,
	const CXXMethodDecl *DerivedMD) {
	QualType BaseReturnTy = BaseMD->getType()
	->getAs<FunctionType>()
	->getReturnType()
	.getCanonicalType();
	QualType DerivedReturnTy = DerivedMD->getType()
	->getAs<FunctionType>()
	->getReturnType()
	.getCanonicalType();

	if (DerivedReturnTy->isDependentType() \|\| BaseReturnTy->isDependentType())
	return false;

	// Check if return types are identical.
	if (Context->hasSameType(DerivedReturnTy, BaseReturnTy))
	return true;

	/// Check if the return types are covariant.

	// Both types must be pointers or references to classes.
	if (!(BaseReturnTy->isPointerType() && DerivedReturnTy->isPointerType()) &&
	!(BaseReturnTy->isReferenceType() && DerivedReturnTy->isReferenceType()))
	return false;

	/// BTy is the class type in return type of BaseMD. For example,
	/// B* Base::md()
	/// While BRD is the declaration of B.
	QualType DTy = DerivedReturnTy->getPointeeType().getCanonicalType();
	QualType BTy = BaseReturnTy->getPointeeType().getCanonicalType();

	const CXXRecordDecl *DRD = DTy->getAsCXXRecordDecl();
	const CXXRecordDecl *BRD = BTy->getAsCXXRecordDecl();
	if (DRD == nullptr \|\| BRD == nullptr)
	return false;

	if (!DRD->hasDefinition() \|\| !BRD->hasDefinition())
	return false;

	if (DRD == BRD)
	return true;

	if (!Context->hasSameUnqualifiedType(DTy, BTy)) {
	// Begin checking whether the conversion from D to B is valid.
	CXXBasePaths Paths(/FindAmbiguities=/true, /RecordPaths=/true,
	/DetectVirtual=/false);

	// Check whether D is derived from B, and fill in a CXXBasePaths object.
	if (!DRD->isDerivedFrom(BRD, Paths))
	return false;

	// Check ambiguity.
	if (Paths.isAmbiguous(Context->getCanonicalType(BTy).getUnqualifiedType()))
	return false;

	// Check accessibility.
	// FIXME: We currently only support checking if B is accessible base class
	// of D, or D is the same class which DerivedMD is in.
	bool IsItself =
	DRD->getCanonicalDecl() == DerivedMD->getParent()->getCanonicalDecl();
	bool HasPublicAccess = false;
	for (const auto &Path : Paths) {
	if (Path.Access == AS_public)
	HasPublicAccess = true;
	}
	if (!HasPublicAccess && !IsItself)
	return false;
	// End checking conversion from D to B.
	}

	// Both pointers or references should have the same cv-qualification.
	if (DerivedReturnTy.getLocalCVRQualifiers() !=
	BaseReturnTy.getLocalCVRQualifiers())
	return false;

	// The class type D should have the same cv-qualification as or less
	// cv-qualification than the class type B.
	if (DTy.isMoreQualifiedThan(BTy))
	return false;

	return true;
	}

	/// \returns decayed type for arrays and functions.
	static QualType getDecayedType(QualType Type) {
	if (const auto *Decayed = Type->getAs<DecayedType>())
	return Decayed->getDecayedType();
	return Type;
	}

	/// \returns true if the param types are the same.
	static bool checkParamTypes(const CXXMethodDecl *BaseMD,
	const CXXMethodDecl *DerivedMD) {
	unsigned NumParamA = BaseMD->getNumParams();
	unsigned NumParamB = DerivedMD->getNumParams();
	if (NumParamA != NumParamB)
	return false;

	for (unsigned I = 0; I < NumParamA; I++) {
	if (getDecayedType(BaseMD->getParamDecl(I)->getType().getCanonicalType()) !=
	getDecayedType(
	DerivedMD->getParamDecl(I)->getType().getCanonicalType()))
	return false;
	}
	return true;
	}

	/// \returns true if derived method can override base method except for the
	/// name.
	static bool checkOverrideWithoutName(const ASTContext *Context,
	const CXXMethodDecl *BaseMD,
	const CXXMethodDecl *DerivedMD) {
	if (BaseMD->isStatic() != DerivedMD->isStatic())
	return false;

	if (BaseMD->getType() == DerivedMD->getType())
	return true;

	// Now the function types are not identical. Then check if the return types
	// are covariant and if the param types are the same.
	if (!checkOverridingFunctionReturnType(Context, BaseMD, DerivedMD))
	return false;
	return checkParamTypes(BaseMD, DerivedMD);
	}

	/// Check whether BaseMD overrides DerivedMD.
	///
	/// Prerequisite: the class which BaseMD is in should be a base class of that
	/// DerivedMD is in.
	static bool checkOverrideByDerivedMethod(const CXXMethodDecl *BaseMD,
	const CXXMethodDecl *DerivedMD) {
	for (CXXMethodDecl::method_iterator I = DerivedMD->begin_overridden_methods(),
	E = DerivedMD->end_overridden_methods();
	I != E; ++I) {
	const CXXMethodDecl OverriddenMD = I;
	if (BaseMD->getCanonicalDecl() == OverriddenMD->getCanonicalDecl())
	return true;
	}

	return false;
	}

	bool VirtualNearMissCheck::isPossibleToBeOverridden(
	const CXXMethodDecl *BaseMD) {
	auto Iter = PossibleMap.find(BaseMD);
	if (Iter != PossibleMap.end())
	return Iter->second;

	bool IsPossible = !BaseMD->isImplicit() && !isa<CXXConstructorDecl>(BaseMD) &&
	!isa<CXXDestructorDecl>(BaseMD) && BaseMD->isVirtual() &&
	!BaseMD->isOverloadedOperator() &&
	!isa<CXXConversionDecl>(BaseMD);
	PossibleMap[BaseMD] = IsPossible;
	return IsPossible;
	}

	bool VirtualNearMissCheck::isOverriddenByDerivedClass(
	const CXXMethodDecl BaseMD, const CXXRecordDecl DerivedRD) {
	auto Key = std::make_pair(BaseMD, DerivedRD);
	auto Iter = OverriddenMap.find(Key);
	if (Iter != OverriddenMap.end())
	return Iter->second;

	bool IsOverridden = false;
	for (const CXXMethodDecl *DerivedMD : DerivedRD->methods()) {
	if (!isOverrideMethod(DerivedMD))
	continue;

	if (checkOverrideByDerivedMethod(BaseMD, DerivedMD)) {
	IsOverridden = true;
	break;
	}
	}
	OverriddenMap[Key] = IsOverridden;
	return IsOverridden;
	}

	void VirtualNearMissCheck::registerMatchers(MatchFinder *Finder) {
	if (!getLangOpts().CPlusPlus)
	return;

	Finder->addMatcher(
	cxxMethodDecl(
	unless(anyOf(isOverride(), isImplicit(), cxxConstructorDecl(),
	cxxDestructorDecl(), cxxConversionDecl(), isStatic(),
	isOverloadedOperator())))
	.bind("method"),
	this);
	}

	void VirtualNearMissCheck::check(const MatchFinder::MatchResult &Result) {
	const auto *DerivedMD = Result.Nodes.getNodeAs<CXXMethodDecl>("method");
	assert(DerivedMD);

	const ASTContext *Context = Result.Context;

	const auto *DerivedRD = DerivedMD->getParent()->getDefinition();
	assert(DerivedRD);

	for (const auto &BaseSpec : DerivedRD->bases()) {
	if (const auto *BaseRD = BaseSpec.getType()->getAsCXXRecordDecl()) {
	for (const auto *BaseMD : BaseRD->methods()) {
	if (!isPossibleToBeOverridden(BaseMD))
	continue;

	if (isOverriddenByDerivedClass(BaseMD, DerivedRD))
	continue;

	unsigned EditDistance = BaseMD->getName().edit_distance(
	DerivedMD->getName(), EditDistanceThreshold);
	if (EditDistance > 0 && EditDistance <= EditDistanceThreshold) {
	if (checkOverrideWithoutName(Context, BaseMD, DerivedMD)) {
	// A "virtual near miss" is found.
	auto Range = CharSourceRange::getTokenRange(
	SourceRange(DerivedMD->getLocation()));

	bool ApplyFix = !BaseMD->isTemplateInstantiation() &&
	!DerivedMD->isTemplateInstantiation();
	auto Diag =
	diag(DerivedMD->getBeginLoc(),
	"method '%0' has a similar name and the same signature as "
	"virtual method '%1'; did you mean to override it?")
	<< DerivedMD->getQualifiedNameAsString()
	<< BaseMD->getQualifiedNameAsString();
	if (ApplyFix)
	Diag << FixItHint::CreateReplacement(Range, BaseMD->getName());
	}
	}
	}
	}
	}
	}

	} // namespace bugprone
	} // namespace tidy
	} // namespace clang