Author: Jerin Philip Date: 2023-11-07T08:27:41-05:00 New Revision: 2e7913342eb9d5cd1744d4c24e1898588429b80d
URL: https://github.com/llvm/llvm-project/commit/2e7913342eb9d5cd1744d4c24e1898588429b80d DIFF: https://github.com/llvm/llvm-project/commit/2e7913342eb9d5cd1744d4c24e1898588429b80d.diff LOG: [clang] Improve `_Alignas` on a `struct` declaration diagnostic (#65638) Fixes https://github.com/llvm/llvm-project/issues/58637. Adds `isAlignas()` method on `AttributeCommonInfo` which accounts for C++ `alignas` as well as C11 `_Alignas`. The method is used to improve diagnostic in C when `_Alignas` is used in C at the wrong location. This corrects the previously suggested move of `_Alignas` past the declaration specifier, now warns attribute `_Alignas` is ignored. Based on https://reviews.llvm.org/D141177. Added: clang/test/Parser/c2x-alignas.c Modified: clang/docs/ReleaseNotes.rst clang/include/clang/Basic/AttributeCommonInfo.h clang/lib/Sema/SemaDecl.cpp clang/test/C/drs/dr4xx.c clang/test/Parser/c1x-alignas.c clang/test/Parser/cxx0x-attributes.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 5e19dbea6608486..8bac599f88503af 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -292,6 +292,11 @@ Attribute Changes in Clang When viewing ``S::FruitKind`` in a debugger, it will behave as if the member was declared as type ``E`` rather than ``unsigned``. +- Clang now warns you that the ``_Alignas`` attribute on declaration specifiers + is ignored, changed from the former incorrect suggestion to move it past + declaration specifiers. (`#58637 <https://github.com/llvm/llvm-project/issues/58637>`_) + + Improvements to Clang's diagnostics ----------------------------------- - Clang constexpr evaluator now prints template arguments when displaying diff --git a/clang/include/clang/Basic/AttributeCommonInfo.h b/clang/include/clang/Basic/AttributeCommonInfo.h index 908e0c71544279c..3140d1a838afcec 100644 --- a/clang/include/clang/Basic/AttributeCommonInfo.h +++ b/clang/include/clang/Basic/AttributeCommonInfo.h @@ -200,6 +200,15 @@ class AttributeCommonInfo { bool isC23Attribute() const { return SyntaxUsed == AS_C23; } + bool isAlignas() const { + // FIXME: In the current state, the IsAlignas member variable is only true + // with the C++ `alignas` keyword but not `_Alignas`. The following + // expression works around the otherwise lost information so it will return + // true for `alignas` or `_Alignas` while still returning false for things + // like `__attribute__((aligned))`. + return (getParsedKind() == AT_Aligned && isKeywordAttribute()); + } + /// The attribute is spelled [[]] in either C or C++ mode, including standard /// attributes spelled with a keyword, like alignas. bool isStandardAttributeSyntax() const { diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 396566a8f10a9b7..7a424eaa5fe7d8e 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -5346,16 +5346,21 @@ Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, TypeSpecType == DeclSpec::TST_interface || TypeSpecType == DeclSpec::TST_union || TypeSpecType == DeclSpec::TST_enum) { - for (const ParsedAttr &AL : DS.getAttributes()) - Diag(AL.getLoc(), AL.isRegularKeywordAttribute() - ? diag::err_declspec_keyword_has_no_effect - : diag::warn_declspec_attribute_ignored) - << AL << GetDiagnosticTypeSpecifierID(DS); - for (const ParsedAttr &AL : DeclAttrs) - Diag(AL.getLoc(), AL.isRegularKeywordAttribute() - ? diag::err_declspec_keyword_has_no_effect - : diag::warn_declspec_attribute_ignored) + + auto EmitAttributeDiagnostic = [this, &DS](const ParsedAttr &AL) { + unsigned DiagnosticId = diag::warn_declspec_attribute_ignored; + if (AL.isAlignas() && !getLangOpts().CPlusPlus) + DiagnosticId = diag::warn_attribute_ignored; + else if (AL.isRegularKeywordAttribute()) + DiagnosticId = diag::err_declspec_keyword_has_no_effect; + else + DiagnosticId = diag::warn_declspec_attribute_ignored; + Diag(AL.getLoc(), DiagnosticId) << AL << GetDiagnosticTypeSpecifierID(DS); + }; + + llvm::for_each(DS.getAttributes(), EmitAttributeDiagnostic); + llvm::for_each(DeclAttrs, EmitAttributeDiagnostic); } } diff --git a/clang/test/C/drs/dr4xx.c b/clang/test/C/drs/dr4xx.c index b8ccceaad12c59f..30145dcfeef1686 100644 --- a/clang/test/C/drs/dr4xx.c +++ b/clang/test/C/drs/dr4xx.c @@ -164,11 +164,7 @@ void dr444(void) { /* FIXME: This should be accepted as per this DR. */ int j = (_Alignas(int) int){12}; /* expected-error {{expected expression}} */ - /* FIXME: The diagnostic in this case is really bad; moving the specifier to - * where the diagnostic recommends causes a diff erent, more inscrutable error - * about anonymous structures. - */ - _Alignas(int) struct T { /* expected-warning {{attribute '_Alignas' is ignored, place it after "struct" to apply attribute to type declaration}} */ + _Alignas(int) struct T { /* expected-warning {{'_Alignas' attribute ignored}} */ int i; }; diff --git a/clang/test/Parser/c1x-alignas.c b/clang/test/Parser/c1x-alignas.c index 8f3d9bdb62d477a..bf08aabc94a8d09 100644 --- a/clang/test/Parser/c1x-alignas.c +++ b/clang/test/Parser/c1x-alignas.c @@ -9,5 +9,6 @@ char c4 _Alignas(32); // expected-error {{expected ';' after top level declarato char _Alignas(_Alignof(int)) c5; +_Alignas(int) struct c6; // expected-warning {{'_Alignas' attribute ignored}} // CHECK-EXT: '_Alignas' is a C11 extension // CHECK-EXT: '_Alignof' is a C11 extension diff --git a/clang/test/Parser/c2x-alignas.c b/clang/test/Parser/c2x-alignas.c new file mode 100644 index 000000000000000..6b02b94c0a295b0 --- /dev/null +++ b/clang/test/Parser/c2x-alignas.c @@ -0,0 +1,11 @@ +// RUN: %clang_cc1 -std=c23 -fsyntax-only -verify %s + +_Alignas(int) struct c1; // expected-warning {{'_Alignas' attribute ignored}} + +// FIXME: `alignas` enters into C++ parsing code and never reaches the +// declaration specifier attribute diagnostic infrastructure. +// +// Fixing this will require the C23 notions of `alignas` being a keyword and +// `_Alignas` being an alternate spelling integrated into the parsing +// infrastructure. +alignas(int) struct c1; // expected-error {{misplaced attributes; expected attributes here}} diff --git a/clang/test/Parser/cxx0x-attributes.cpp b/clang/test/Parser/cxx0x-attributes.cpp index 10c5bbcac10227b..fad3010c98b9c28 100644 --- a/clang/test/Parser/cxx0x-attributes.cpp +++ b/clang/test/Parser/cxx0x-attributes.cpp @@ -451,3 +451,5 @@ namespace P2361 { // expected-warning {{use of the 'deprecated' attribute is a C++14 extension}} [[nodiscard("\123")]] int b(); // expected-error{{invalid escape sequence '\123' in an unevaluated string literal}} } + +alignas(int) struct AlignAsAttribute {}; // expected-error {{misplaced attributes; expected attributes here}} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
