https://github.com/v1nh1shungry created
https://github.com/llvm/llvm-project/pull/153941
```cpp
struct Base {
int m;
};
template <class T>
struct Derived : Base {
Derived() { m = 0; }
};
```
would previously generate the following output:
```
<source>:7:15: warning: 'm' should be initialized in a member initializer of
the constructor [cppcoreguidelines-prefer-member-initializer]
7 | Derived() { m = 0; }
| ^~~~~~
| : m(0)
```
This patch fixes this false positive.
Note that before this patch the checker won't give false positive for
```cpp
struct Derived : Base {
Derived() { m = 0; }
};
```
and the constructor's AST is
```
`-CXXConstructorDecl 0x557df03d1fb0 <line:7:3, col:22> col:3 Derived 'void ()'
implicit-inline
|-CXXCtorInitializer 'Base'
| `-CXXConstructExpr 0x557df03d2748 <col:3> 'Base' 'void () noexcept'
`-CompoundStmt 0x557df03d2898 <col:13, col:22>
`-BinaryOperator 0x557df03d2878 <col:15, col:19> 'int' lvalue '='
|-MemberExpr 0x557df03d2828 <col:15> 'int' lvalue ->m 0x557df03d1c40
| `-ImplicitCastExpr 0x557df03d2808 <col:15> 'Base *'
<UncheckedDerivedToBase (Base)>
| `-CXXThisExpr 0x557df03d27f8 <col:15> 'Derived *' implicit this
`-IntegerLiteral 0x557df03d2858 <col:19> 'int' 0
```
so `isAssignmentToMemberOf` would return empty due to
https://github.com/llvm/llvm-project/blob/f0967fca04c880e9aabd5be043a85127faabb4c6/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp#L118-L119
>From 6c6ceab3d9a08052c00b308305720f2b0f8c70eb Mon Sep 17 00:00:00 2001
From: Yuanjing Hong <[email protected]>
Date: Fri, 15 Aug 2025 15:59:35 +0800
Subject: [PATCH] [clang-tidy] Fix
`cppcoreguidelines-prefer-member-initializer` false positive for inherited
members
```cpp
struct Base {
int m;
};
template <class T>
struct Derived : Base {
Derived() { m = 0; }
};
```
would previously generate the following output:
```
<source>:7:15: warning: 'm' should be initialized in a member initializer of
the constructor [cppcoreguidelines-prefer-member-initializer]
7 | Derived() { m = 0; }
| ^~~~~~
| : m(0)
```
This patch fixes this false positive.
---
.../PreferMemberInitializerCheck.cpp | 3 +++
clang-tools-extra/docs/ReleaseNotes.rst | 4 ++++
.../prefer-member-initializer.cpp | 17 +++++++++++++++++
3 files changed, 24 insertions(+)
diff --git
a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
index 593a4f85d1309..79cd4bbcc9a60 100644
---
a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
+++
b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
@@ -191,6 +191,9 @@ void PreferMemberInitializerCheck::check(
if (!AssignmentToMember)
continue;
const FieldDecl *Field = AssignmentToMember->Field;
+ // Skip if the field is inherited from a base class.
+ if (Field->getParent() != Class)
+ continue;
const Expr *InitValue = AssignmentToMember->Init;
updateAssignmentLevel(Field, InitValue, Ctor, AssignedFields);
if (!canAdvanceAssignment(AssignedFields[Field]))
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst
b/clang-tools-extra/docs/ReleaseNotes.rst
index 1553f461634d0..0d5dbd85df6a4 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -163,6 +163,10 @@ Changes in existing checks
an additional matcher that generalizes the copy-and-swap idiom pattern
detection.
+- Improved :doc:`cppcoreguidelines-prefer-member-initializer
+ <clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>` check by
+ no longer giving false positives for inherited members.
+
- Improved :doc:`misc-header-include-cycle
<clang-tidy/checks/misc/header-include-cycle>` check performance.
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer.cpp
b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer.cpp
index 7d6164946fc3d..faff4882142f1 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer.cpp
@@ -650,3 +650,20 @@ struct InitFromBindingDecl {
}
};
} // namespace GH82970
+
+namespace inherited_members {
+
+struct A {
+ int m;
+};
+
+struct B : A {
+ B() { m = 0; }
+};
+
+template <class T>
+struct C : A {
+ C() { m = 0; }
+};
+
+} // namespace inherited_members
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