Index: clang-tidy/cppcoreguidelines/CMakeLists.txt =================================================================== --- clang-tidy/cppcoreguidelines/CMakeLists.txt +++ clang-tidy/cppcoreguidelines/CMakeLists.txt @@ -3,6 +3,7 @@ add_clang_library(clangTidyCppCoreGuidelinesModule CppCoreGuidelinesTidyModule.cpp ProTypeReinterpretCastCheck.cpp + ProTypeStaticCastDowncastCheck.cpp LINK_LIBS clangAST Index: clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp =================================================================== --- clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp +++ clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp @@ -11,6 +11,7 @@ #include "../ClangTidyModule.h" #include "../ClangTidyModuleRegistry.h" #include "ProTypeReinterpretCastCheck.h" +#include "ProTypeStaticCastDowncastCheck.h" namespace clang { namespace tidy { @@ -21,6 +22,8 @@ void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override { CheckFactories.registerCheck( "cppcoreguidelines-pro-type-reinterpret-cast"); + CheckFactories.registerCheck( + "cppcoreguidelines-pro-type-static-cast-downcast"); } }; Index: clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h =================================================================== --- /dev/null +++ clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h @@ -0,0 +1,34 @@ +//===--- ProTypeStaticCastDowncastCheck.h - clang-tidy-----------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_STATIC_CAST_DOWNCAST_H +#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_STATIC_CAST_DOWNCAST_H + +#include "../ClangTidy.h" + +namespace clang { +namespace tidy { + +/// Checks for usages of static_cast, where a base class is downcasted to a derived class. +/// +/// For the user-facing documentation see: +/// http://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines-pro-type-static-cast-downcast.html +class ProTypeStaticCastDowncastCheck : public ClangTidyCheck { +public: + ProTypeStaticCastDowncastCheck(StringRef Name, ClangTidyContext *Context) + : ClangTidyCheck(Name, Context) {} + void registerMatchers(ast_matchers::MatchFinder *Finder) override; + void check(const ast_matchers::MatchFinder::MatchResult &Result) override; +}; + +} // namespace tidy +} // namespace clang + +#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_TYPE_STATIC_CAST_DOWNCAST_H + Index: clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp =================================================================== --- /dev/null +++ clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp @@ -0,0 +1,62 @@ +//===--- ProTypeStaticCastDowncastCheck.cpp - clang-tidy-------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "ProTypeStaticCastDowncastCheck.h" +#include "clang/AST/ASTContext.h" +#include "clang/ASTMatchers/ASTMatchFinder.h" + +using namespace clang::ast_matchers; + +namespace clang { +namespace tidy { + +void ProTypeStaticCastDowncastCheck::registerMatchers(MatchFinder *Finder) { + if (!getLangOpts().CPlusPlus) + return; + + Finder->addMatcher(cxxStaticCastExpr().bind("cast"), this); +} + +void ProTypeStaticCastDowncastCheck::check(const MatchFinder::MatchResult &Result) { + const auto *MatchedCast = Result.Nodes.getNodeAs("cast"); + + auto SubExpr = MatchedCast->getSubExpr(); + if (SubExpr->isTypeDependent()) + return; + + SubExpr = SubExpr->IgnoreParens(); + QualType SourceType = SubExpr->getType(); + + QualType DestType = MatchedCast->getTypeAsWritten(); + if (!DestType->isPointerType() && !DestType->isReferenceType()) + return; + auto DestDecl = DestType->getPointeeCXXRecordDecl(); + + const CXXRecordDecl* SourceDecl; + if (SourceType->isPointerType()) + SourceDecl = SourceType->getPointeeCXXRecordDecl(); + else + SourceDecl = SourceType->getAsCXXRecordDecl(); + + if(!SourceDecl) + return; + + if (DestDecl->isDerivedFrom(SourceDecl)) { + diag(MatchedCast->getOperatorLoc(), "do not use static_cast to cast from base to derived. Use " + "dynamic_cast instead. (C++ Core " + "Guidelines, rule Type.2)") + << FixItHint::CreateReplacement( + {MatchedCast->getOperatorLoc(), MatchedCast->getOperatorLoc()}, + "dynamic_cast"); + } +} + +} // namespace tidy +} // namespace clang + Index: docs/clang-tidy/checks/cppcoreguidelines-pro-type-static-cast-downcast.rst =================================================================== --- /dev/null +++ docs/clang-tidy/checks/cppcoreguidelines-pro-type-static-cast-downcast.rst @@ -0,0 +1,10 @@ +cppcoreguidelines-pro-type-static-cast-downcast +=============================================== + +This check flags all usages of static_cast, where a base class is casted to a derived class. +In those cases, a fixit is provided to convert the cast to a dynamic_cast. + +Use of these casts can violate type safety and cause the program to access a variable that is actually of type X to be accessed as if it were of an unrelated type Z. + +This rule is part of the "Type safety" profile of the C++ Core Guidelines, see +https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-type2-dont-use-static_cast-downcasts-use-dynamic_cast-instead Index: docs/clang-tidy/checks/list.rst =================================================================== --- docs/clang-tidy/checks/list.rst +++ docs/clang-tidy/checks/list.rst @@ -3,6 +3,7 @@ .. toctree:: cppcoreguidelines-pro-type-reinterpret-cast + cppcoreguidelines-pro-type-static-cast-downcast google-build-explicit-make-pair google-build-namespaces google-build-using-namespace Index: test/clang-tidy/cppcoreguidelines-pro-type-static-cast-downcast.cpp =================================================================== --- /dev/null +++ test/clang-tidy/cppcoreguidelines-pro-type-static-cast-downcast.cpp @@ -0,0 +1,60 @@ +// RUN: %python %S/check_clang_tidy.py %s cppcoreguidelines-pro-type-static-cast-downcast %t + +class Base { +}; + +class Derived : public Base { +}; + +class Base2 { +}; + +class MultiDerived : public Base, public Base2 { +}; + +void pointers() { + + auto B0 = static_cast(new Base()); + // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use static_cast to cast from base to derived. Use dynamic_cast instead. (C++ Core Guidelines, rule Type.2) [cppcoreguidelines-pro-type-static-cast-downcast] + // CHECK-FIXES: auto B0 = dynamic_cast(new Base()); + + auto B1 = static_cast(new Derived()); // OK, upcast to a public base + auto B2 = static_cast(new MultiDerived()); // OK, upcast to a public base + auto B3 = static_cast(new MultiDerived()); // OK, upcast to a public base +} + +void arrays() { + Base ArrayOfBase[10]; + auto D0 = static_cast(ArrayOfBase); + // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use static_cast to cast from base to derived. Use dynamic_cast instead. (C++ Core Guidelines, rule Type.2) [cppcoreguidelines-pro-type-static-cast-downcast] + // CHECK-FIXES: auto D0 = dynamic_cast(ArrayOfBase); +} + +void references() { + Base B0; + Base& RefToBase = B0; + auto D0 = static_cast(RefToBase); + // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use static_cast to cast from base to derived. Use dynamic_cast instead. (C++ Core Guidelines, rule Type.2) [cppcoreguidelines-pro-type-static-cast-downcast] + // CHECK-FIXES: auto D0 = dynamic_cast(RefToBase); + + Derived d1; + auto b1 = static_cast(d1); // OK, upcast to a public base +} + +template +void templ_bad() { + auto B0 = static_cast(new D()); + // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: do not use static_cast to cast from base to derived. Use dynamic_cast instead. (C++ Core Guidelines, rule Type.2) [cppcoreguidelines-pro-type-static-cast-downcast] + // CHECK-FIXES: auto B0 = dynamic_cast(new D()); +} +void templ_bad_call() { + templ_bad(); +} + +template +void templ_good() { + auto B1 = static_cast(new D()); +} +void templ_good_call() { + templ_good(); // OK, upcast to a public base +}