https://github.com/tigbr updated
https://github.com/llvm/llvm-project/pull/135831
>From 525459a04dd6e7d0079095ac531c7cd712ac91d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=A1bor=20T=C3=B3thv=C3=A1ri?=
<gabor.tothv...@ericsson.com>
Date: Mon, 14 Apr 2025 17:09:07 +0200
Subject: [PATCH] [clang-tidy] Fix bugprone-tagged-union-member-count
false-positive
Types from system headers and the std namespace are no longer considered as
the enum part or the union part of a user-defined tagged union.
Fixes #134840
---
.../bugprone/TaggedUnionMemberCountCheck.cpp | 12 ++++++----
.../bugprone/tagged-union-member-count.rst | 22 +++++++++++++++++++
.../bugprone/tagged-union-member-count.c | 13 +++++++++++
.../bugprone/tagged-union-member-count.cpp | 13 +++++++++++
.../bugprone/tagged-union-member-count.m | 13 +++++++++++
.../bugprone/tagged-union-member-count.mm | 13 +++++++++++
6 files changed, 82 insertions(+), 4 deletions(-)
diff --git
a/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.cpp
b/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.cpp
index db99ef3786e5f..b91da7db39463 100644
--- a/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.cpp
@@ -106,11 +106,15 @@ void TaggedUnionMemberCountCheck::storeOptions(
void TaggedUnionMemberCountCheck::registerMatchers(MatchFinder *Finder) {
- auto UnionField = fieldDecl(hasType(qualType(
- hasCanonicalType(recordType(hasDeclaration(recordDecl(isUnion())))))));
+ auto NotFromSystemHeaderOrStdNamespace =
+ unless(anyOf(isExpansionInSystemHeader(), isInStdNamespace()));
- auto EnumField = fieldDecl(hasType(
- qualType(hasCanonicalType(enumType(hasDeclaration(enumDecl()))))));
+ auto UnionField =
+ fieldDecl(hasType(qualType(hasCanonicalType(recordType(hasDeclaration(
+ recordDecl(isUnion(), NotFromSystemHeaderOrStdNamespace)))))));
+
+ auto EnumField = fieldDecl(hasType(qualType(hasCanonicalType(
+
enumType(hasDeclaration(enumDecl(NotFromSystemHeaderOrStdNamespace)))))));
auto hasOneUnionField = fieldCountOfKindIsOne(UnionField,
UnionMatchBindName);
auto hasOneEnumField = fieldCountOfKindIsOne(EnumField, TagMatchBindName);
diff --git
a/clang-tools-extra/docs/clang-tidy/checks/bugprone/tagged-union-member-count.rst
b/clang-tools-extra/docs/clang-tidy/checks/bugprone/tagged-union-member-count.rst
index 2f1036c10345e..b47a49543143b 100644
---
a/clang-tools-extra/docs/clang-tidy/checks/bugprone/tagged-union-member-count.rst
+++
b/clang-tools-extra/docs/clang-tidy/checks/bugprone/tagged-union-member-count.rst
@@ -9,6 +9,9 @@ different from the number of data members inside the union.
A struct or a class is considered to be a tagged union if it has
exactly one union data member and exactly one enum data member and
any number of other data members that are neither unions or enums.
+The union and enum data members that are from system header files or
+the std namespace are not considered to make up the tagged union part
+of a user-defined tagged union type.
Example:
@@ -28,6 +31,25 @@ Example:
} Data;
};
+The following example illustrates the exception for unions and enums from
+system header files and the std namespace.
+
+.. code-block:: c++
+
+ #include <pthread.h>
+
+ struct NotTaggedUnion {
+ enum MyEnum { MyEnumConstant1, MyEnumConstant2 } En;
+ pthread_mutex_t Mutex;
+ };
+
+The pthread_mutex_t type may be defined as a union behind a typedef,
+in which case the check could mistake this type as a user-defined tagged union.
+After all it has exactly one enum data member and exactly one union data
member.
+To avoid false-positive cases originating from this, unions and enums from
+system headers and the std namespace are ignored when pinpointing the
+union part and the enum part of a potential user-defined tagged union.
+
How enum constants are counted
------------------------------
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.c
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.c
index 60c93c553baca..96255c7fdd4fe 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.c
+++
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.c
@@ -147,3 +147,16 @@ struct Name {\
// CHECK-MESSAGES: :[[@LINE+1]]:44: warning: tagged union has more data
members (4) than tags (3)
DECLARE_TAGGED_UNION_STRUCT(Tags3, Union4, TaggedUnionStructFromMacro);
+
+// Typedefed unions from system header files should be ignored when
+// we are trying to pinpoint the union part in a user-defined tagged union.
+#include "pthread.h"
+
+// This should not be analyzed as a user-defined tagged union,
+// even though pthread_mutex_t may be declared as a typedefed union.
+struct SystemTypedefedUnionDataMemberShouldBeIgnored {
+ pthread_mutex_t Mutex;
+ enum {
+ MyEnum
+ } EnumField;
+};
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.cpp
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.cpp
index 25827e8c8de0c..f21c23b87ae44 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.cpp
+++
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.cpp
@@ -308,3 +308,16 @@ void DoNotMatchLambdas() {
} u;
auto L = [e, u] () {};
}
+
+// Typedefed unions from system header files should be ignored when
+// we are trying to pinpoint the union part in a user-defined tagged union.
+#include "pthread.h"
+
+// This should not be analyzed as a user-defined tagged union,
+// even though pthread_mutex_t may be declared as a typedefed union.
+struct SystemTypedefedUnionDataMemberShouldBeIgnored {
+ pthread_mutex_t Mutex;
+ enum {
+ MyEnum
+ } EnumField;
+};
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.m
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.m
index 60c93c553baca..96255c7fdd4fe 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.m
+++
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.m
@@ -147,3 +147,16 @@
// CHECK-MESSAGES: :[[@LINE+1]]:44: warning: tagged union has more data
members (4) than tags (3)
DECLARE_TAGGED_UNION_STRUCT(Tags3, Union4, TaggedUnionStructFromMacro);
+
+// Typedefed unions from system header files should be ignored when
+// we are trying to pinpoint the union part in a user-defined tagged union.
+#include "pthread.h"
+
+// This should not be analyzed as a user-defined tagged union,
+// even though pthread_mutex_t may be declared as a typedefed union.
+struct SystemTypedefedUnionDataMemberShouldBeIgnored {
+ pthread_mutex_t Mutex;
+ enum {
+ MyEnum
+ } EnumField;
+};
diff --git
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.mm
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.mm
index 8b308555281c5..b169b5cd480b5 100644
---
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.mm
+++
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.mm
@@ -307,3 +307,16 @@ void DoNotMatchLambdas() {
} u;
auto L = [e, u] () {};
}
+
+// Typedefed unions from system header files should be ignored when
+// we are trying to pinpoint the union part in a user-defined tagged union.
+#include "pthread.h"
+
+// This should not be analyzed as a user-defined tagged union,
+// even though pthread_mutex_t may be declared as a typedefed union.
+struct SystemTypedefedUnionDataMemberShouldBeIgnored {
+ pthread_mutex_t Mutex;
+ enum {
+ MyEnum
+ } EnumField;
+};
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