diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td --- a/clang/include/clang/Basic/Attr.td +++ b/clang/include/clang/Basic/Attr.td @@ -2944,7 +2944,7 @@ C2x<"", "nodiscard", 201904>, CXX11<"clang", "warn_unused_result">, GCC<"warn_unused_result">]; - let Subjects = SubjectList<[ObjCMethod, Enum, Record, FunctionLike]>; + let Subjects = SubjectList<[ObjCMethod, Enum, Record, FunctionLike, TypedefName]>; let Args = [StringArgument<"Message", 1>]; let Documentation = [WarnUnusedResultsDocs]; let AdditionalMembers = [{ diff --git a/clang/include/clang/Basic/AttributeCommonInfo.h b/clang/include/clang/Basic/AttributeCommonInfo.h --- a/clang/include/clang/Basic/AttributeCommonInfo.h +++ b/clang/include/clang/Basic/AttributeCommonInfo.h @@ -146,6 +146,7 @@ bool isMicrosoftAttribute() const { return SyntaxUsed == AS_Microsoft; } bool isGNUScope() const; + bool isClangScope() const; bool isAlignasAttribute() const { // FIXME: Use a better mechanism to determine this. @@ -164,6 +165,8 @@ return isCXX11Attribute() || isC2xAttribute(); } + bool isGNUAttribute() const { return SyntaxUsed == AS_GNU; } + bool isKeywordAttribute() const { return SyntaxUsed == AS_Keyword || SyntaxUsed == AS_ContextSensitiveKeyword; } diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -8734,6 +8734,10 @@ def warn_unused_result_msg : Warning< "ignoring return value of function declared with %0 attribute: %1">, InGroup; +def warn_unused_result_typedef_unsupported_spelling : Warning< + "'[[%select{nodiscard|gnu::warn_unused_result}0]]' attribute ignored when " + "applied to a typedef; consider using '__attribute__((warn_unused_result))' " + "or '[[clang::warn_unused_result]]' instead">, InGroup; def warn_unused_volatile : Warning< "expression result unused; assign into a variable to force a volatile load">, InGroup>; diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp --- a/clang/lib/AST/Expr.cpp +++ b/clang/lib/AST/Expr.cpp @@ -1522,6 +1522,11 @@ if (const auto *A = TD->getAttr()) return A; + for (const auto *TD = getCallReturnType(Ctx)->getAs(); TD; + TD = TD->desugar()->getAs()) + if (const auto *A = TD->getDecl()->getAttr()) + return A; + // Otherwise, see if the callee is marked nodiscard and return that attribute // instead. const Decl *D = getCalleeDecl(); diff --git a/clang/lib/Basic/Attributes.cpp b/clang/lib/Basic/Attributes.cpp --- a/clang/lib/Basic/Attributes.cpp +++ b/clang/lib/Basic/Attributes.cpp @@ -85,6 +85,10 @@ return ScopeName && (ScopeName->isStr("gnu") || ScopeName->isStr("__gnu__")); } +bool AttributeCommonInfo::isClangScope() const { + return ScopeName && (ScopeName->isStr("clang") || ScopeName->isStr("_Clang")); +} + #include "clang/Sema/AttrParsedAttrKinds.inc" static SmallString<64> normalizeName(const IdentifierInfo *Name, diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp --- a/clang/lib/Sema/SemaDeclAttr.cpp +++ b/clang/lib/Sema/SemaDeclAttr.cpp @@ -3156,6 +3156,14 @@ S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL; } + if ((!AL.isGNUAttribute() && + !(AL.isStandardAttributeSyntax() && AL.isClangScope())) && + isa(D)) { + S.Diag(AL.getLoc(), diag::warn_unused_result_typedef_unsupported_spelling) + << AL.isGNUScope(); + return; + } + D->addAttr(::new (S.Context) WarnUnusedResultAttr(S.Context, AL, Str)); } diff --git a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p1.cpp b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p1.cpp --- a/clang/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p1.cpp +++ b/clang/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p1.cpp @@ -7,4 +7,4 @@ [[nodiscard]] int f(); enum [[nodiscard]] E {}; -namespace [[nodiscard]] N {} // expected-warning {{'nodiscard' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, and function pointers}} +namespace [[nodiscard]] N {} // expected-warning {{'nodiscard' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, function pointers, and typedefs}} diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test --- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test +++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test @@ -185,7 +185,7 @@ // CHECK-NEXT: VecReturn (SubjectMatchRule_record) // CHECK-NEXT: VecTypeHint (SubjectMatchRule_function) // CHECK-NEXT: WarnUnused (SubjectMatchRule_record) -// CHECK-NEXT: WarnUnusedResult (SubjectMatchRule_objc_method, SubjectMatchRule_enum, SubjectMatchRule_record, SubjectMatchRule_hasType_functionType) +// CHECK-NEXT: WarnUnusedResult (SubjectMatchRule_objc_method, SubjectMatchRule_enum, SubjectMatchRule_record, SubjectMatchRule_hasType_functionType, SubjectMatchRule_type_alias) // CHECK-NEXT: Weak (SubjectMatchRule_variable, SubjectMatchRule_function, SubjectMatchRule_record) // CHECK-NEXT: WeakRef (SubjectMatchRule_variable, SubjectMatchRule_function) // CHECK-NEXT: WebAssemblyExportName (SubjectMatchRule_function) diff --git a/clang/test/Sema/c2x-nodiscard.c b/clang/test/Sema/c2x-nodiscard.c --- a/clang/test/Sema/c2x-nodiscard.c +++ b/clang/test/Sema/c2x-nodiscard.c @@ -15,7 +15,7 @@ [[nodiscard]] int f1(void); enum [[nodiscard]] E1 { One }; -[[nodiscard]] int i; // expected-warning {{'nodiscard' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, and function pointers}} +[[nodiscard]] int i; // expected-warning {{'nodiscard' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, function pointers, and typedefs}} struct [[nodiscard]] S4 { int i; diff --git a/clang/test/Sema/unused-expr.c b/clang/test/Sema/unused-expr.c --- a/clang/test/Sema/unused-expr.c +++ b/clang/test/Sema/unused-expr.c @@ -96,7 +96,7 @@ return 0; } -int t7 __attribute__ ((warn_unused_result)); // expected-warning {{'warn_unused_result' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, and function pointers}} +int t7 __attribute__ ((warn_unused_result)); // expected-warning {{'warn_unused_result' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, function pointers, and typedefs}} // PR4010 int (*fn4)(void) __attribute__ ((warn_unused_result)); diff --git a/clang/test/SemaCXX/warn-unused-result.cpp b/clang/test/SemaCXX/warn-unused-result.cpp --- a/clang/test/SemaCXX/warn-unused-result.cpp +++ b/clang/test/SemaCXX/warn-unused-result.cpp @@ -254,3 +254,35 @@ void i([[nodiscard]] bool (*fp)()); // expected-warning {{'nodiscard' attribute only applies to functions, classes, or enumerations}} } + +namespace unused_typedef_result { +[[clang::warn_unused_result]] typedef void *a; +typedef a indirect; +a af1(); +indirect indirectf1(); +void af2() { + af1(); // expected-warning {{ignoring return value}} + void *(*a1)(); + a1(); // no warning + a (*a2)(); + a2(); // expected-warning {{ignoring return value}} + indirectf1(); // expected-warning {{ignoring return value}} +} +[[nodiscard]] typedef void *b1; // expected-warning {{'[[nodiscard]]' attribute ignored when applied to a typedef; consider using '__attribute__((warn_unused_result))' or '[[clang::warn_unused_result]]' instead}} +[[gnu::warn_unused_result]] typedef void *b2; // expected-warning {{'[[gnu::warn_unused_result]]' attribute ignored when applied to a typedef; consider using '__attribute__((warn_unused_result))' or '[[clang::warn_unused_result]]' instead}} +b1 b1f1(); +b2 b2f1(); +void bf2() { + b1f1(); // no warning + b2f1(); // no warning +} +__attribute__((warn_unused_result)) typedef void *c; +c cf1(); +void cf2() { + cf1(); // expected-warning {{ignoring return value}} + void *(*c1)(); + c1(); + c (*c2)(); + c2(); // expected-warning {{ignoring return value}} +} +}