diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index ad524ad3c5bbb..f8581b190e939 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -822,6 +822,7 @@ 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). - Fixed a bug where Clang hung on an unsupported optional scope specifier ``::`` when parsing Objective-C. Clang now emits a diagnostic message instead of hanging. diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp index 97954a2b3c6db..e4e3bbad1f520 100644 --- a/clang/lib/Sema/SemaDeclCXX.cpp +++ b/clang/lib/Sema/SemaDeclCXX.cpp @@ -3316,6 +3316,29 @@ void Sema::CheckShadowInheritedFields(const SourceLocation &Loc, } } +template +inline static bool HasAttribute(const QualType &T) { + if (const TagDecl *TD = T->getAsTagDecl()) + return TD->hasAttr(); + if (const TypedefType *TDT = T->getAs()) + return TDT->getDecl()->hasAttr(); + return false; +} + +static bool IsUnusedPrivateField(const FieldDecl *FD) { + if (FD->getAccess() == AS_private && FD->getDeclName()) { + QualType FieldType = FD->getType(); + if (HasAttribute(FieldType)) + return true; + + return !FD->isImplicit() && !FD->hasAttr() && + !FD->getParent()->isDependentContext() && + !HasAttribute(FieldType) && + !InitializationHasSideEffects(*FD); + } + return false; +} + NamedDecl * Sema::ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS, Declarator &D, MultiTemplateParamsArg TemplateParameterLists, @@ -3598,25 +3621,11 @@ Sema::ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS, Declarator &D, FieldDecl *FD = cast(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(); - if (const TypedefType *TDT = T->getAs()) - return TDT->getDecl()->hasAttr(); - return false; - }; - - if (!FD->isImplicit() && FD->getDeclName() && - FD->getAccess() == AS_private && - !FD->hasAttr() && - !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 0cc6f687f1b35..0bcca6b82227f 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 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 @@ -329,3 +329,28 @@ class C { MaybeUnusedTypedef t; // no-warning }; } + +namespace GH62472 { +class [[gnu::warn_unused]] S { +public: + 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}} + 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 +}; +}