[clang-tidy] Fix cppcoreguidelines-pro-type-member-init check (llvm#169832)

Closes [llvm#169677](llvm#169677)

---------

Co-authored-by: EugeneZelenko <[email protected]>

Author: 2 people

clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp

@@ -361,7 +361,8 @@ void ProTypeMemberInitCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
 }
 
 // FIXME: Copied from clang/lib/Sema/SemaDeclCXX.cpp.
-static bool isIncompleteOrZeroLengthArrayType(ASTContext &Context, QualType T) {
+static bool isIncompleteOrZeroLengthArrayType(const ASTContext &Context,
+                                              QualType T) {
   if (T->isIncompleteArrayType())
     return true;
 
@@ -375,7 +376,7 @@ static bool isIncompleteOrZeroLengthArrayType(ASTContext &Context, QualType T) {
   return false;
 }
 
-static bool isEmpty(ASTContext &Context, const QualType &Type) {
+static bool isEmpty(const ASTContext &Context, const QualType &Type) {
   if (const CXXRecordDecl *ClassDecl = Type->getAsCXXRecordDecl()) {
     return ClassDecl->isEmpty();
   }
@@ -431,19 +432,13 @@ static llvm::StringLiteral getInitializer(QualType QT, bool UseAssignment) {
   }
 }
 
-void ProTypeMemberInitCheck::checkMissingMemberInitializer(
-    ASTContext &Context, const CXXRecordDecl &ClassDecl,
-    const CXXConstructorDecl *Ctor) {
-  const bool IsUnion = ClassDecl.isUnion();
-
-  if (IsUnion && ClassDecl.hasInClassInitializer())
-    return;
-
-  // Gather all fields (direct and indirect) that need to be initialized.
-  SmallPtrSet<const FieldDecl *, 16> FieldsToInit;
+static void
+computeFieldsToInit(const ASTContext &Context, const RecordDecl &Record,
+                    bool IgnoreArrays,
+                    SmallPtrSetImpl<const FieldDecl *> &FieldsToInit) {
   bool AnyMemberHasInitPerUnion = false;
   forEachFieldWithFilter(
-      ClassDecl, ClassDecl.fields(), AnyMemberHasInitPerUnion,
+      Record, Record.fields(), AnyMemberHasInitPerUnion,
       [&](const FieldDecl *F) {
         if (IgnoreArrays && F->getType()->isArrayType())
           return;
@@ -458,6 +453,19 @@ void ProTypeMemberInitCheck::checkMissingMemberInitializer(
             !AnyMemberHasInitPerUnion)
           FieldsToInit.insert(F);
       });
+}
+
+void ProTypeMemberInitCheck::checkMissingMemberInitializer(
+    ASTContext &Context, const CXXRecordDecl &ClassDecl,
+    const CXXConstructorDecl *Ctor) {
+  const bool IsUnion = ClassDecl.isUnion();
+
+  if (IsUnion && ClassDecl.hasInClassInitializer())
+    return;
+
+  // Gather all fields (direct and indirect) that need to be initialized.
+  SmallPtrSet<const FieldDecl *, 16> FieldsToInit;
+  computeFieldsToInit(Context, ClassDecl, IgnoreArrays, FieldsToInit);
   if (FieldsToInit.empty())
     return;
 
@@ -507,7 +515,7 @@ void ProTypeMemberInitCheck::checkMissingMemberInitializer(
   // Collect all fields but only suggest a fix for the first member of unions,
   // as initializing more than one union member is an error.
   SmallPtrSet<const FieldDecl *, 16> FieldsToFix;
-  AnyMemberHasInitPerUnion = false;
+  bool AnyMemberHasInitPerUnion = false;
   forEachFieldWithFilter(ClassDecl, ClassDecl.fields(),
                          AnyMemberHasInitPerUnion, [&](const FieldDecl *F) {
                            if (!FieldsToInit.contains(F))
@@ -582,6 +590,17 @@ void ProTypeMemberInitCheck::checkMissingBaseClassInitializer(
 
 void ProTypeMemberInitCheck::checkUninitializedTrivialType(
     const ASTContext &Context, const VarDecl *Var) {
+  // Verify that the record actually needs initialization
+  const CXXRecordDecl *Record = Var->getType()->getAsCXXRecordDecl();
+  if (!Record)
+    return;
+
+  SmallPtrSet<const FieldDecl *, 16> FieldsToInit;
+  computeFieldsToInit(Context, *Record, IgnoreArrays, FieldsToInit);
+
+  if (FieldsToInit.empty())
+    return;
+
   const DiagnosticBuilder Diag =
       diag(Var->getBeginLoc(), "uninitialized record type: %0") << Var;
 

clang-tools-extra/docs/ReleaseNotes.rst

@@ -424,6 +424,11 @@ Changes in existing checks
   adding an option to allow pointer arithmetic via prefix/postfix increment or
   decrement operators.
 
+- Improved :doc:`cppcoreguidelines-pro-type-member-init
+  <clang-tidy/checks/cppcoreguidelines/pro-type-member-init>` check to
+  correctly ignore ``std::array`` and other array-like containers when
+  `IgnoreArrays` option is set to `true`.
+
 - Improved :doc:`google-readability-casting
   <clang-tidy/checks/google/readability-casting>` check by adding fix-it
   notes for downcasts and casts to void pointer.

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-member-init.ignorearrays.cpp

@@ -14,3 +14,39 @@ struct HasArrayMember {
   int RawArray[4];
   int Number;
 };
+
+namespace std {
+template <typename T, int N>
+struct array {
+  T _Elems[N];
+  void fill(const T &);
+};
+}
+
+void test_local_std_array() {
+  std::array<int, 4> a;
+}
+
+struct OnlyArray {
+  int a[4];
+};
+
+void test_local_only_array() {
+  OnlyArray a;
+}
+
+struct Mixed {
+  int a[4];
+  int b;
+};
+
+void test_local_mixed() {
+  Mixed m;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: uninitialized record type: 'm'
+}
+
+void test_std_array_fill() {
+  std::array<char, 10> someArray;
+  // CHECK-MESSAGES-NOT: warning: uninitialized record type: 'someArray'
+  someArray.fill('n');
+}