https://github.com/a-tarasyuk updated
https://github.com/llvm/llvm-project/pull/120734
>From 55fb96c1673911f30721c2a53bea32e7e4b5dc6e Mon Sep 17 00:00:00 2001
From: Oleksandr T <oleksandr.taras...@outlook.com>
Date: Fri, 20 Dec 2024 15:32:55 +0200
Subject: [PATCH 1/2] [Clang] handle [[warn_unused]] attribute for unused
private fields
---
clang/docs/ReleaseNotes.rst | 1 +
clang/lib/Sema/SemaDeclCXX.cpp | 43 +++++++++++--------
.../SemaCXX/warn-unused-private-field.cpp | 13 ++++++
3 files changed, 40 insertions(+), 17 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a85ef60b7b58ba..c1d3596140721e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -707,6 +707,7 @@ Improvements to Clang's diagnostics
}
- Fix -Wdangling false positives on conditional operators (#120206).
+- Clang now diagnoses unused private fields with the ``[[warn_unused]]``
attribute (#GH62472).
Improvements to Clang's time-trace
----------------------------------
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index c5a72cf812ebc9..760ed06fc1b858 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -3307,6 +3307,29 @@ void Sema::CheckShadowInheritedFields(const
SourceLocation &Loc,
}
}
+template <typename AttrType>
+inline static bool HasAttribute(const QualType &T) {
+ if (const TagDecl *TD = T->getAsTagDecl())
+ return TD->hasAttr<AttrType>();
+ if (const TypedefType *TDT = T->getAs<TypedefType>())
+ return TDT->getDecl()->hasAttr<AttrType>();
+ return false;
+}
+
+inline static bool IsUnusedPrivateField(FieldDecl *FD) {
+ if (FD->getAccess() == AS_private && FD->getDeclName()) {
+ QualType FieldType = FD->getType();
+ if (HasAttribute<WarnUnusedAttr>(FieldType))
+ return true;
+
+ return !FD->isImplicit() && !FD->hasAttr<UnusedAttr>() &&
+ !FD->getParent()->isDependentContext() &&
+ !HasAttribute<UnusedAttr>(FieldType) &&
+ !InitializationHasSideEffects(*FD);
+ }
+ return false;
+}
+
NamedDecl *
Sema::ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS, Declarator &D,
MultiTemplateParamsArg TemplateParameterLists,
@@ -3589,25 +3612,11 @@ Sema::ActOnCXXMemberDeclarator(Scope *S,
AccessSpecifier AS, Declarator &D,
FieldDecl *FD = cast<FieldDecl>(Member);
FieldCollector->Add(FD);
- if (!Diags.isIgnored(diag::warn_unused_private_field, FD->getLocation())) {
+ if (!Diags.isIgnored(diag::warn_unused_private_field, FD->getLocation()) &&
+ IsUnusedPrivateField(FD)) {
// Remember all explicit private FieldDecls that have a name, no side
// effects and are not part of a dependent type declaration.
-
- auto DeclHasUnusedAttr = [](const QualType &T) {
- if (const TagDecl *TD = T->getAsTagDecl())
- return TD->hasAttr<UnusedAttr>();
- if (const TypedefType *TDT = T->getAs<TypedefType>())
- return TDT->getDecl()->hasAttr<UnusedAttr>();
- return false;
- };
-
- if (!FD->isImplicit() && FD->getDeclName() &&
- FD->getAccess() == AS_private &&
- !FD->hasAttr<UnusedAttr>() &&
- !FD->getParent()->isDependentContext() &&
- !DeclHasUnusedAttr(FD->getType()) &&
- !InitializationHasSideEffects(*FD))
- UnusedPrivateFields.insert(FD);
+ UnusedPrivateFields.insert(FD);
}
}
diff --git a/clang/test/SemaCXX/warn-unused-private-field.cpp
b/clang/test/SemaCXX/warn-unused-private-field.cpp
index 0cc6f687f1b35f..93a285b159f740 100644
--- a/clang/test/SemaCXX/warn-unused-private-field.cpp
+++ b/clang/test/SemaCXX/warn-unused-private-field.cpp
@@ -329,3 +329,16 @@ class C {
MaybeUnusedTypedef t; // no-warning
};
}
+
+namespace GH62472 {
+class [[gnu::warn_unused]] S {
+public:
+ S();
+};
+
+class C {
+private:
+ const int i = 0; // expected-warning {{private field 'i' is not used}}
+ const S s; // expected-warning {{private field 's' is not used}}
+};
+}
>From ff26d33c97f9eaf7c1d2c21cf341cb771d831be5 Mon Sep 17 00:00:00 2001
From: Oleksandr T <oleksandr.taras...@outlook.com>
Date: Sat, 18 Jan 2025 01:46:03 +0200
Subject: [PATCH 2/2] add additional test cases
---
.../SemaCXX/warn-unused-private-field.cpp | 26 ++++++++++++++-----
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/clang/test/SemaCXX/warn-unused-private-field.cpp
b/clang/test/SemaCXX/warn-unused-private-field.cpp
index 93a285b159f740..0bcca6b82227f9 100644
--- a/clang/test/SemaCXX/warn-unused-private-field.cpp
+++ b/clang/test/SemaCXX/warn-unused-private-field.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -fsyntax-only -Wunused-private-field
-Wused-but-marked-unused -Wno-uninitialized -verify -std=c++11 %s
-// RUN: %clang_cc1 -fsyntax-only -Wunused-private-field
-Wused-but-marked-unused -Wno-uninitialized -verify -std=c++17 %s
-// RUN: %clang_cc1 -fsyntax-only -Wunused-private-field
-Wused-but-marked-unused -Wno-uninitialized -verify -std=c++20 %s
+// RUN: %clang_cc1 -fsyntax-only -Wunused -Wused-but-marked-unused
-Wno-uninitialized -verify -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -Wunused -Wused-but-marked-unused
-Wno-uninitialized -verify -std=c++17 %s
+// RUN: %clang_cc1 -fsyntax-only -Wunused -Wused-but-marked-unused
-Wno-uninitialized -verify -std=c++20 %s
#if __cplusplus >= 202002L
@@ -108,7 +108,7 @@ class ClassWithTemplateFriend {
template <typename T> class TemplateFriend {
public:
TemplateFriend(ClassWithTemplateFriend my_friend) {
- int var = my_friend.used_by_friend_;
+ int var = my_friend.used_by_friend_; // expected-warning {{unused variable
'var'}}
}
};
@@ -181,10 +181,10 @@ class EverythingUsed {
public:
EverythingUsed() : as_array_index_(0), var_(by_initializer_) {
var_ = sizeof(sizeof_);
- int *use = &by_reference_;
+ int *use = &by_reference_; // expected-warning {{unused variable 'use'}}
int test[2];
test[as_array_index_] = 42;
- int EverythingUsed::*ptr = &EverythingUsed::by_pointer_to_member_;
+ int EverythingUsed::*ptr = &EverythingUsed::by_pointer_to_member_; //
expected-warning {{unused variable 'ptr'}}
}
template<class T>
@@ -336,9 +336,21 @@ class [[gnu::warn_unused]] S {
S();
};
+struct [[maybe_unused]] T {};
+
+void f() {
+ int i = 0; // expected-warning {{unused variable 'i'}}
+ S s; // expected-warning {{unused variable 's'}}
+ T t; // ok
+}
+
class C {
private:
const int i = 0; // expected-warning {{private field 'i' is not used}}
- const S s; // expected-warning {{private field 's' is not used}}
+ int j = 0; // expected-warning {{private field 'j' is not used}}
+ const S s1; // expected-warning {{private field 's1' is not used}}
+ const T t1; // ok
+ S s2; // expected-warning {{private field 's2' is not used}}
+ T t2; // ok
};
}
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