mgehre created this revision.
mgehre added reviewers: alexfh, sbenza, bkramer, aaron.ballman.
mgehre added a subscriber: cfe-commits.
mgehre added a dependency: D13313: [clang-tidy] new check
cppcoreguidelines-pro-type-reinterpret-cast.
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
Depends on D13313
http://reviews.llvm.org/D13368
Files:
clang-tidy/cppcoreguidelines/CMakeLists.txt
clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp
clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.cpp
clang-tidy/cppcoreguidelines/ProTypeStaticCastDowncastCheck.h
docs/clang-tidy/checks/cppcoreguidelines-pro-type-static-cast-downcast.rst
docs/clang-tidy/checks/list.rst
test/clang-tidy/cppcoreguidelines-pro-type-static-cast-downcast.cpp
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<Derived*>(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<Derived*>(new Base());
+
+ auto B1 = static_cast<Base*>(new Derived()); // OK, upcast to a public base
+ auto B2 = static_cast<Base*>(new MultiDerived()); // OK, upcast to a public base
+ auto B3 = static_cast<Base2*>(new MultiDerived()); // OK, upcast to a public base
+}
+
+void arrays() {
+ Base ArrayOfBase[10];
+ auto D0 = static_cast<Derived*>(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<Derived*>(ArrayOfBase);
+}
+
+void references() {
+ Base B0;
+ Base& RefToBase = B0;
+ auto D0 = static_cast<Derived&>(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<Derived&>(RefToBase);
+
+ Derived d1;
+ auto b1 = static_cast<Base&>(d1); // OK, upcast to a public base
+}
+
+template<class B, class D>
+void templ_bad() {
+ auto B0 = static_cast<B*>(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<B*>(new D());
+}
+void templ_bad_call() {
+ templ_bad<Derived, Base>();
+}
+
+template<class B, class D>
+void templ_good() {
+ auto B1 = static_cast<B*>(new D());
+}
+void templ_good_call() {
+ templ_good<Base, Derived>(); // OK, upcast to a public base
+}
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: 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: 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<CXXStaticCastExpr>("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: 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<ProTypeReinterpretCastCheck>(
"cppcoreguidelines-pro-type-reinterpret-cast");
+ CheckFactories.registerCheck<ProTypeStaticCastDowncastCheck>(
+ "cppcoreguidelines-pro-type-static-cast-downcast");
}
};
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
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