Author: St. Muench Date: 2025-09-07T22:54:37+03:00 New Revision: 6fc32e93066c59a39b3c8c9be4e4f416653a917e
URL: https://github.com/llvm/llvm-project/commit/6fc32e93066c59a39b3c8c9be4e4f416653a917e DIFF: https://github.com/llvm/llvm-project/commit/6fc32e93066c59a39b3c8c9be4e4f416653a917e.diff LOG: [clang-tidy] do not diagnose array types within implicit instantiations of a template (#132924) So far, the clang-tidy check `modernize-avoid-c-arrays` also diagnosed array types for type template parameters even though no actual array type got written there but it got deduced to one. In such case, there is nothing a developer can do at that location to fix the diagnostic. Since in this case, the location where the template got actually instantiated would have to be adjusted. And this is in most cases some totally distant code where implementers of a template do not have access to. Also adding suppressions to the declaration of the template is not an option since that would clutter the code unnecessarily and is in many cases also simply not possible (e.g. for users of a template). Hence, we propose to not diagnose any occurrence of an array type in an implicit instantiation of a template but rather at the point where template arguments involve array types. Added: Modified: clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp clang-tools-extra/docs/ReleaseNotes.rst clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays-ignores-strings.cpp clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays.cpp Removed: ################################################################################ diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp index ee70911dff1d5..a5b535f7433bb 100644 --- a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp +++ b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp @@ -39,6 +39,53 @@ AST_MATCHER(clang::ParmVarDecl, isArgvOfMain) { return FD ? FD->isMain() : false; } +template <typename TargetType, typename NodeType> +const TargetType *getAs(const NodeType *Node) { + if constexpr (std::is_same_v<NodeType, clang::DynTypedNode>) + return Node->template get<TargetType>(); + else + return llvm::dyn_cast<TargetType>(Node); +} + +AST_MATCHER(clang::TypeLoc, isWithinImplicitTemplateInstantiation) { + const auto IsImplicitTemplateInstantiation = [](const auto *Node) { + const auto IsImplicitInstantiation = [](const auto *Node) { + return (Node != nullptr) && (Node->getTemplateSpecializationKind() == + TSK_ImplicitInstantiation); + }; + return (IsImplicitInstantiation(getAs<clang::CXXRecordDecl>(Node)) || + IsImplicitInstantiation(getAs<clang::FunctionDecl>(Node)) || + IsImplicitInstantiation(getAs<clang::VarDecl>(Node))); + }; + + DynTypedNodeList ParentNodes = Finder->getASTContext().getParents(Node); + const clang::NamedDecl *ParentDecl = nullptr; + while (!ParentNodes.empty()) { + const DynTypedNode &ParentNode = ParentNodes[0]; + if (IsImplicitTemplateInstantiation(&ParentNode)) + return true; + + // in case of a `NamedDecl` as parent node, it is more efficient to proceed + // with the upward traversal via DeclContexts (see below) instead of via + // parent nodes + if ((ParentDecl = ParentNode.template get<clang::NamedDecl>())) + break; + + ParentNodes = Finder->getASTContext().getParents(ParentNode); + } + + if (ParentDecl != nullptr) { + const clang::DeclContext *DeclContext = ParentDecl->getDeclContext(); + while (DeclContext != nullptr) { + if (IsImplicitTemplateInstantiation(DeclContext)) + return true; + DeclContext = DeclContext->getParent(); + } + } + + return false; +} + } // namespace AvoidCArraysCheck::AvoidCArraysCheck(StringRef Name, ClangTidyContext *Context) @@ -66,22 +113,38 @@ void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) { hasParent(varDecl(isExternC())), hasParent(fieldDecl( hasParent(recordDecl(isExternCContext())))), - hasAncestor(functionDecl(isExternC())))), + hasAncestor(functionDecl(isExternC())), + isWithinImplicitTemplateInstantiation())), IgnoreStringArrayIfNeededMatcher) .bind("typeloc"), this); + + Finder->addMatcher( + templateArgumentLoc(hasTypeLoc( + typeLoc(hasType(arrayType())).bind("template_arg_array_typeloc"))), + this); } void AvoidCArraysCheck::check(const MatchFinder::MatchResult &Result) { - const auto *ArrayType = Result.Nodes.getNodeAs<TypeLoc>("typeloc"); + TypeLoc ArrayTypeLoc{}; + + if (const auto *MatchedTypeLoc = Result.Nodes.getNodeAs<TypeLoc>("typeloc")) + ArrayTypeLoc = *MatchedTypeLoc; + + if (const auto *TemplateArgArrayTypeLoc = + Result.Nodes.getNodeAs<TypeLoc>("template_arg_array_typeloc")) + ArrayTypeLoc = *TemplateArgArrayTypeLoc; + + assert(!ArrayTypeLoc.isNull()); + const bool IsInParam = Result.Nodes.getNodeAs<ParmVarDecl>("param_decl") != nullptr; - const bool IsVLA = ArrayType->getTypePtr()->isVariableArrayType(); + const bool IsVLA = ArrayTypeLoc.getTypePtr()->isVariableArrayType(); enum class RecommendType { Array, Vector, Span }; llvm::SmallVector<const char *> RecommendTypes{}; if (IsVLA) { RecommendTypes.push_back("'std::vector'"); - } else if (ArrayType->getTypePtr()->isIncompleteArrayType() && IsInParam) { + } else if (ArrayTypeLoc.getTypePtr()->isIncompleteArrayType() && IsInParam) { // in function parameter, we also don't know the size of // IncompleteArrayType. if (Result.Context->getLangOpts().CPlusPlus20) @@ -93,9 +156,11 @@ void AvoidCArraysCheck::check(const MatchFinder::MatchResult &Result) { } else { RecommendTypes.push_back("'std::array'"); } - diag(ArrayType->getBeginLoc(), + + diag(ArrayTypeLoc.getBeginLoc(), "do not declare %select{C-style|C VLA}0 arrays, use %1 instead") - << IsVLA << llvm::join(RecommendTypes, " or "); + << IsVLA << llvm::join(RecommendTypes, " or ") + << ArrayTypeLoc.getSourceRange(); } } // namespace clang::tidy::modernize diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst index e1b6daf75457d..62916906f96fe 100644 --- a/clang-tools-extra/docs/ReleaseNotes.rst +++ b/clang-tools-extra/docs/ReleaseNotes.rst @@ -218,6 +218,10 @@ Changes in existing checks - Improved :doc:`misc-header-include-cycle <clang-tidy/checks/misc/header-include-cycle>` check performance. +- Improved :doc:`modernize-avoid-c-arrays + <clang-tidy/checks/modernize/avoid-c-arrays>` to not diagnose array types + which are part of an implicit instantiation of a template. + - Improved :doc:`modernize-use-constraints <clang-tidy/checks/modernize/use-constraints>` check by fixing a crash on uses of non-standard ``enable_if`` with a signature diff erent from diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays-ignores-strings.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays-ignores-strings.cpp index 906663828a547..18458bd47d347 100644 --- a/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays-ignores-strings.cpp +++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays-ignores-strings.cpp @@ -7,3 +7,15 @@ const char array[] = {'n', 'a', 'm', 'e', '\0'}; void takeCharArray(const char name[]); // CHECK-MESSAGES: :[[@LINE-1]]:26: warning: do not declare C-style arrays, use 'std::array' or 'std::vector' instead [modernize-avoid-c-arrays] + +template <typename T = const char[10], typename U = char[10], char[10]> +// CHECK-MESSAGES: :[[@LINE-1]]:30: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +// CHECK-MESSAGES: :[[@LINE-2]]:53: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +// CHECK-MESSAGES: :[[@LINE-3]]:63: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +void func() {} + +template <typename T = const char[], typename U = char[], char[]> +// CHECK-MESSAGES: :[[@LINE-1]]:30: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +// CHECK-MESSAGES: :[[@LINE-2]]:51: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +// CHECK-MESSAGES: :[[@LINE-3]]:59: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +void fun() {} diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays.cpp index 14eb2852c639a..95e04d53eb6ac 100644 --- a/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays.cpp +++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-arrays.cpp @@ -32,7 +32,14 @@ array<int[4], 2> d; using k = int[4]; // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: do not declare C-style arrays, use 'std::array' instead +k ak; +// no diagnostic expected here since no concrete C-style array type is written here + array<k, 2> dk; +// no diagnostic expected here since no concrete C-style array type is written here + +array<decltype(ak), 3> ek; +// no diagnostic expected here since no concrete C-style array type is written here template <typename T> class unique_ptr { @@ -92,3 +99,188 @@ const char name[] = "Some string"; void takeCharArray(const char name[]); // CHECK-MESSAGES: :[[@LINE-1]]:26: warning: do not declare C-style arrays, use 'std::array' or 'std::vector' instead [modernize-avoid-c-arrays] + +namespace std { + template<class T, class U> + struct is_same { constexpr static bool value{false}; }; + + template<class T> + struct is_same<T, T> { constexpr static bool value{true}; }; + + template<class T, class U> + constexpr bool is_same_v = is_same<T, U>::value; + + template<class T> struct remove_const { typedef T type; }; + template<class T> struct remove_const<const T> { typedef T type; }; + + template<class T> + using remove_const_t = typename remove_const<T>::type; + + template<bool B, class T = void> struct enable_if {}; + template<class T> struct enable_if<true, T> { typedef T type; }; + + template< bool B, class T = void > + using enable_if_t = typename enable_if<B, T>::type; +} + +// within below template decl, no array type findings are expected within the template parameter declarations since not a single C-style array type got written explicitly +template <typename T, + bool = std::is_same_v<T, int>, + bool = std::is_same<T, int>::value, + bool = std::is_same_v<std::remove_const_t<T>, int>, + bool = std::is_same<std::remove_const_t<T>, int>::value, + bool = std::is_same_v<typename std::remove_const<T>::type, int>, + bool = std::is_same<typename std::remove_const<T>::type, int>::value, + std::enable_if_t<not(std::is_same_v<std::remove_const_t<T>, int>) && not(std::is_same_v<typename std::remove_const<T>::type, char>), bool> = true, + typename std::enable_if<not(std::is_same_v<std::remove_const_t<T>, int>) && not(std::is_same_v<typename std::remove_const<T>::type, char>), bool>::type = true, + typename = std::enable_if_t<not(std::is_same_v<std::remove_const_t<T>, int>) && not(std::is_same_v<typename std::remove_const<T>::type, char>)>, + typename = typename std::remove_const<T>::type, + typename = std::remove_const_t<T>> +class MyClassTemplate { + public: + // here, however, plenty of array type findings are expected for below template parameter declarations since C-style array types are written explicitly + template <typename U = T, + bool = std::is_same_v<U, int[]>, + // CHECK-MESSAGES: :[[@LINE-1]]:38: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + bool = std::is_same<U, int[10]>::value, + // CHECK-MESSAGES: :[[@LINE-1]]:36: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + std::enable_if_t<not(std::is_same_v<std::remove_const_t<U>, int[]>) && not(std::is_same_v<typename std::remove_const<U>::type, char[10]>), bool> = true, + // CHECK-MESSAGES: :[[@LINE-1]]:73: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + // CHECK-MESSAGES: :[[@LINE-2]]:140: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + typename = typename std::remove_const<int[10]>::type, + // CHECK-MESSAGES: :[[@LINE-1]]:51: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + typename = std::remove_const_t<int[]>> + // CHECK-MESSAGES: :[[@LINE-1]]:44: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + class MyInnerClassTemplate { + public: + MyInnerClassTemplate(const U&) {} + private: + U field[3]; + // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + }; + + MyClassTemplate(const T&) {} + + private: + T field[7]; + // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +}; + +// an explicit instantiation +template +class MyClassTemplate<int[2]>; +// CHECK-MESSAGES: :[[@LINE-1]]:23: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + +using MyArrayType = int[3]; +// CHECK-MESSAGES: :[[@LINE-1]]:21: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + +// another explicit instantiation +template +class MyClassTemplate<MyArrayType>; +// no diagnostic is expected here since no C-style array type got written here + +// within below template decl, no array type findings are expected within the template parameter declarations since not a single C-style array type got written explicitly +template <typename T, + bool = std::is_same_v<T, int>, + bool = std::is_same<T, int>::value, + bool = std::is_same_v<std::remove_const_t<T>, int>, + bool = std::is_same<std::remove_const_t<T>, int>::value, + bool = std::is_same_v<typename std::remove_const<T>::type, int>, + bool = std::is_same<typename std::remove_const<T>::type, int>::value, + std::enable_if_t<not(std::is_same_v<std::remove_const_t<T>, int>) && not(std::is_same_v<typename std::remove_const<T>::type, char>), bool> = true, + typename std::enable_if<not(std::is_same_v<std::remove_const_t<T>, int>) && not(std::is_same_v<typename std::remove_const<T>::type, char>), bool>::type = true, + typename = std::enable_if_t<not(std::is_same_v<std::remove_const_t<T>, int>) && not(std::is_same_v<typename std::remove_const<T>::type, char>)>, + typename = typename std::remove_const<T>::type, + typename = std::remove_const_t<T>> +void func(const T& param) { + int array1[1]; + // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + T array2[2]; + // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + T value; +} + +// here, however, plenty of array type findings are expected for below template parameter declarations since C-style array types are written explicitly +template <typename T = int[], + // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + bool = std::is_same_v<T, int[]>, + // CHECK-MESSAGES: :[[@LINE-1]]:36: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + bool = std::is_same<T, int[10]>::value, + // CHECK-MESSAGES: :[[@LINE-1]]:34: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + std::enable_if_t<not(std::is_same_v<std::remove_const_t<T>, int[]>) && not(std::is_same_v<typename std::remove_const<T>::type, char[10]>), bool> = true, + // CHECK-MESSAGES: :[[@LINE-1]]:71: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + // CHECK-MESSAGES: :[[@LINE-2]]:138: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + typename = typename std::remove_const<int[10]>::type, + // CHECK-MESSAGES: :[[@LINE-1]]:49: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + typename = std::remove_const_t<int[]>> + // CHECK-MESSAGES: :[[@LINE-1]]:42: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +void fun(const T& param) { + int array3[3]; + // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + T array4[4]; + // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + T value; +} + +template<typename T> +T some_constant{}; + +// explicit instantiations +template +int some_constant<int[5]>[5]; +// CHECK-MESSAGES: :[[@LINE-1]]:19: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + +template +int some_constant<decltype(ak)>[4]; +// no diagnostic is expected here since explicit instantiations aren't represented as `TypeLoc` in the AST and we hence cannot match them as such + +MyArrayType mk; +// no diagnostic is expected here since no C-style array type got written here + +// explicit specializations +template<> +int some_constant<int[7]>[7]{}; +// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +// CHECK-MESSAGES: :[[@LINE-2]]:19: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + +template<> +int some_constant<decltype(mk)>[3]{}; +// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + +void testArrayInTemplateType() { + int t[10]; + // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + func(t); + fun(t); + + func<decltype(t)>({}); + fun<decltype(t)>({}); + + func<int[1]>({}); + // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + fun<int[1]>({}); + // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + MyClassTemplate var{t}; + MyClassTemplate<decltype(t)> var1{{}}; + MyClassTemplate<int[2]> var2{{}}; + // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + decltype(var1)::MyInnerClassTemplate var3{t}; + decltype(var1)::MyInnerClassTemplate<decltype(t)> var4{{}}; + decltype(var1)::MyInnerClassTemplate<char[5]> var5{{}}; + // CHECK-MESSAGES: :[[@LINE-1]]:40: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + + MyClassTemplate<decltype(t)>::MyInnerClassTemplate var6{t}; + MyClassTemplate<decltype(t)>::MyInnerClassTemplate<decltype(t)> var7{{}}; + MyClassTemplate<decltype(t)>::MyInnerClassTemplate<char[8]> var8{{}}; + // CHECK-MESSAGES: :[[@LINE-1]]:54: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + MyClassTemplate<int[9]>::MyInnerClassTemplate<char[9]> var9{{}}; + // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] + // CHECK-MESSAGES: :[[@LINE-2]]:49: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays] +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
