[Clang] handle [[warn_unused]] attribute for unused private fields #120734
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
clang
|
@llvm/pr-subscribers-clang Author: Oleksandr T. (a-tarasyuk) ChangesFixes #62472 Full diff: https://github.com/llvm/llvm-project/pull/120734.diff 3 Files Affected:
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}}
+};
+}
|
a-tarasyuk
commented
Dec 20, 2024
erichkeane
reviewed
Dec 20, 2024
tbaederr
reviewed
Jan 19, 2025
erichkeane
approved these changes
Jan 28, 2025
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/12607 Here is the relevant piece of the build log for the reference |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #62472