[clang-tools-extra] [clang-tidy] Fix `cppcoreguidelines-pro-type-member-init` check (PR #169832)

[via cfe-commits]

https://github.com/zeyi2 updated https://github.com/llvm/llvm-project/pull/169832

>From f41310dcb601075d980c4d7163d8db1d5dee7913 Mon Sep 17 00:00:00 2001
From: mtx <mitchell.xu2 at gmail.com>
Date: Thu, 27 Nov 2025 23:50:47 +0800
Subject: [PATCH 1/2] [clang-tidy] Fix `cppcoreguidelines-pro-type-member-init`
 check

---
 .../ProTypeMemberInitCheck.cpp                | 32 +++++++++++++++--
 clang-tools-extra/docs/ReleaseNotes.rst       |  5 +++
 .../pro-type-member-init.ignorearrays.cpp     | 36 +++++++++++++++++++
 3 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
index 66508da89f0dd..f8c096b4b4c66 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
+++ b/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();
   }
@@ -582,6 +583,33 @@ 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;
+  bool AnyMemberHasInitPerUnion = false;
+  forEachFieldWithFilter(
+      *Record, Record->fields(), AnyMemberHasInitPerUnion,
+      [&](const FieldDecl *F) {
+        if (IgnoreArrays && F->getType()->isArrayType())
+          return;
+        if (F->hasInClassInitializer() && F->getParent()->isUnion()) {
+          AnyMemberHasInitPerUnion = true;
+          removeFieldInitialized(F, FieldsToInit);
+        }
+        if (!F->hasInClassInitializer() &&
+            utils::type_traits::isTriviallyDefaultConstructible(F->getType(),
+                                                                Context) &&
+            !isEmpty(Context, F->getType()) && !F->isUnnamedBitField() &&
+            !AnyMemberHasInitPerUnion)
+          FieldsToInit.insert(F);
+      });
+
+  if (FieldsToInit.empty())
+    return;
+
   const DiagnosticBuilder Diag =
       diag(Var->getBeginLoc(), "uninitialized record type: %0") << Var;
 
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index a6f80e3721db1..3ad2ffc07da5c 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/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 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.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-member-init.ignorearrays.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-member-init.ignorearrays.cpp
index 01859b3ad98f4..e4cfe679cfce9 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/pro-type-member-init.ignorearrays.cpp
+++ b/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');
+}

>From 29f44eb8f8ff90eac085670c0ee9b4c07a589717 Mon Sep 17 00:00:00 2001
From: mitchell <mitchell.xu2 at gmail.com>
Date: Fri, 28 Nov 2025 13:33:37 +0800
Subject: [PATCH 2/2] Update clang-tools-extra/docs/ReleaseNotes.rst

Co-authored-by: EugeneZelenko <eugene.zelenko at gmail.com>
---
 clang-tools-extra/docs/ReleaseNotes.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 3ad2ffc07da5c..edb2a98446eba 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -426,8 +426,8 @@ Changes in existing checks
 
 - Improved :doc:`cppcoreguidelines-pro-type-member-init
   <clang-tidy/checks/cppcoreguidelines/pro-type-member-init>` check to
-  correctly ignore ``std::array`` and other containers when ``IgnoreArrays``
-  option is set to ``true``.
+  correctly ignore ``std::array`` and other containers when `IgnoreArrays`
+  option is set to `true`.
 
 - Improved :doc:`google-readability-casting
   <clang-tidy/checks/google/readability-casting>` check by adding fix-it