[CLANG] Enable alignas after GNU attributes

clang/docs/ReleaseNotes.rst

@@ -428,6 +428,7 @@ Bug Fixes to C++ Support
 - Clang no longer crashes when establishing subsumption between some constraint expressions. (#GH122581)
 - Clang now issues an error when placement new is used to modify a const-qualified variable
   in a ``constexpr`` function. (#GH131432)
+- Clang now correctly parses arbitrary order of ``[[]]``, ``__attribute__`` and ``alignas`` attributes for declarations (#GH133107)
 - Clang now emits a warning when class template argument deduction for alias templates is used in C++17. (#GH133806)
 
 Bug Fixes to AST Handling

clang/include/clang/Parse/Parser.h

@@ -3062,13 +3062,16 @@ class Parser : public CodeCompletionHandler {
                             bool CouldBeBitField = false);
   Decl *ParseHLSLBuffer(SourceLocation &DeclEnd);
 
-  void MaybeParseMicrosoftAttributes(ParsedAttributes &Attrs) {
+  bool MaybeParseMicrosoftAttributes(ParsedAttributes &Attrs) {
+    bool AttrsParsed = false;
     if ((getLangOpts().MicrosoftExt || getLangOpts().HLSL) &&
         Tok.is(tok::l_square)) {
       ParsedAttributes AttrsWithRange(AttrFactory);
       ParseMicrosoftAttributes(AttrsWithRange);
+      AttrsParsed = AttrsWithRange.size();
       Attrs.takeAllFrom(AttrsWithRange);
     }
+    return AttrsParsed;
   }
   void ParseMicrosoftUuidAttributeArgs(ParsedAttributes &Attrs);
   void ParseMicrosoftAttributes(ParsedAttributes &Attrs);

clang/lib/Parse/ParseDeclCXX.cpp

@@ -3035,11 +3035,14 @@ Parser::DeclGroupPtrTy Parser::ParseCXXClassMemberDeclaration(
   }
 
   ParsedAttributes DeclSpecAttrs(AttrFactory);
-  MaybeParseMicrosoftAttributes(DeclSpecAttrs);
-
   // Hold late-parsed attributes so we can attach a Decl to them later.
   LateParsedAttrList CommonLateParsedAttrs;
 
+  while (MaybeParseCXX11Attributes(DeclAttrs) ||
+         MaybeParseGNUAttributes(DeclSpecAttrs, &CommonLateParsedAttrs) ||
+         MaybeParseMicrosoftAttributes(DeclSpecAttrs))
+    ;
+
   // decl-specifier-seq:
   // Parse the common declaration-specifiers piece.
   ParsingDeclSpec DS(*this, TemplateDiags);

clang/lib/Parse/ParseStmt.cpp

@@ -235,6 +235,9 @@ StmtResult Parser::ParseStatementOrDeclarationAfterAttributes(
   }
 
   default: {
+    if (getLangOpts().CPlusPlus && MaybeParseCXX11Attributes(CXX11Attrs, true))
+      goto Retry;
+
     bool HaveAttrs = !CXX11Attrs.empty() || !GNUAttrs.empty();
     auto IsStmtAttr = [](ParsedAttr &Attr) { return Attr.isStmtAttr(); };
     bool AllAttrsAreStmtAttrs = llvm::all_of(CXX11Attrs, IsStmtAttr) &&
@@ -260,11 +263,11 @@ StmtResult Parser::ParseStatementOrDeclarationAfterAttributes(
                                 GNUAttrs);
       }
       if (CXX11Attrs.Range.getBegin().isValid()) {
-        // The caller must guarantee that the CXX11Attrs appear before the
-        // GNUAttrs, and we rely on that here.
-        assert(GNUAttrs.Range.getBegin().isInvalid() ||
-               GNUAttrs.Range.getBegin() > CXX11Attrs.Range.getBegin());
-        DeclStart = CXX11Attrs.Range.getBegin();
+        // Order of C++11 and GNU attributes is may be arbitrary.
+        DeclStart = GNUAttrs.Range.getBegin().isInvalid()
+                        ? CXX11Attrs.Range.getBegin()
+                        : std::min(CXX11Attrs.Range.getBegin(),
+                                   GNUAttrs.Range.getBegin());
       } else if (GNUAttrs.Range.getBegin().isValid())
         DeclStart = GNUAttrs.Range.getBegin();
       return Actions.ActOnDeclStmt(Decl, DeclStart, DeclEnd);

clang/test/AST/ast-dump-color.cpp

@@ -91,7 +91,7 @@ struct Invalid {
 //CHECK: {{^}}[[Blue]]|   `-[[RESET]][[MAGENTA]]DeclRefExpr[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]col:40[[RESET]]> [[Green]]'class Mutex':'Mutex'[[RESET]][[Cyan]] lvalue[[RESET]][[Cyan]][[RESET]] [[GREEN]]Var[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]][[CYAN]] 'mu1'[[RESET]] [[Green]]'class Mutex':'Mutex'[[RESET]] non_odr_use_unevaluated{{$}}
 //CHECK: {{^}}[[Blue]]|-[[RESET]][[GREEN]]CXXRecordDecl[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]line:28:1[[RESET]], [[Yellow]]line:30:1[[RESET]]> [[Yellow]]line:28:8[[RESET]] struct[[CYAN]] Invalid[[RESET]] definition
 //CHECK: {{^}}[[Blue]]| |-[[RESET]][[GREEN]]CXXRecordDecl[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]col:1[[RESET]], [[Yellow]]col:8[[RESET]]> [[Yellow]]col:8[[RESET]] implicit referenced struct[[CYAN]] Invalid[[RESET]]
-//CHECK: {{^}}[[Blue]]| |-[[RESET]][[GREEN]]CXXConstructorDecl[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]line:29:3[[RESET]], [[Yellow]]col:42[[RESET]]> [[Yellow]]col:29[[RESET]] invalid[[CYAN]] Invalid[[RESET]] [[Green]]'void (int)'[[RESET]]
+//CHECK: {{^}}[[Blue]]| |-[[RESET]][[GREEN]]CXXConstructorDecl[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]line:29:29[[RESET]], [[Yellow]]col:42[[RESET]]> [[Yellow]]col:29[[RESET]] invalid[[CYAN]] Invalid[[RESET]] [[Green]]'void (int)'[[RESET]]
 //CHECK: {{^}}[[Blue]]| | |-[[RESET]][[GREEN]]ParmVarDecl[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]col:37[[RESET]], [[Yellow]]<invalid sloc>[[RESET]]> [[Yellow]]col:42[[RESET]] invalid [[Green]]'int'[[RESET]]
 //CHECK: {{^}}[[Blue]]| | `-[[RESET]][[BLUE]]NoInlineAttr[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]col:18[[RESET]]>
 //CHECK: {{^}}[[Blue]]| |-[[RESET]][[GREEN]]CXXConstructorDecl[[RESET]][[Yellow]] 0x{{[0-9a-fA-F]*}}[[RESET]] <[[Yellow]]line:28:8[[RESET]]> [[Yellow]]col:8[[RESET]] implicit used constexpr[[CYAN]] Invalid[[RESET]] [[Green]]'void () noexcept'[[RESET]] inline

clang/test/Index/annotate-attribute.cpp

@@ -24,7 +24,7 @@ int templateFunction(T value) __attribute__((annotate("works")));
 
 // CHECK: ClassDecl=Test:3:7 (Definition) Extent=[3:1 - 17:2]
 // CHECK-NEXT: CXXAccessSpecifier=:4:1 (Definition) Extent=[4:1 - 4:8]
-// CHECK-NEXT: CXXMethod=aMethod:5:51 Extent=[5:3 - 5:60]
+// CHECK-NEXT: CXXMethod=aMethod:5:51 Extent=[5:46 - 5:60]
 // CHECK-NEXT: attribute(annotate)=spiffy_method Extent=[5:18 - 5:43]
 // CHECK-NEXT: CXXAccessSpecifier=:7:1 (Definition) Extent=[7:1 - 7:43]
 // CHECK-NEXT: attribute(annotate)=works Extent=[7:23 - 7:40]

clang/test/Parser/c2x-alignas.c

@@ -2,3 +2,26 @@
 
 _Alignas(int) struct c1; // expected-warning {{'_Alignas' attribute ignored}}
 alignas(int) struct c1; // expected-warning {{'alignas' attribute ignored}}
+
+
+__attribute__(()) [[]] alignas(int) int a; // expected-none TODO: actually this line should be an error
+__attribute__(()) alignas(int) [[]] int b; // expected-error {{an attribute list cannot appear here}}
+__attribute__(()) alignas(int) int c; // expected-none
+[[]] __attribute__(()) alignas(int) int d; // expected-none
+alignas(int) [[]] __attribute__(()) int e; // expected-error {{an attribute list cannot appear here}}
+
+struct C1 {
+    __attribute__(()) [[]] alignas(int) int a; // expected-error {{an attribute list cannot appear here}}
+    __attribute__(()) alignas(int) [[]] int b; // expected-error {{an attribute list cannot appear here}}
+    __attribute__(()) alignas(int) int c; // expected-none
+    [[]] __attribute__(()) alignas(int) int d; // expected-none
+    alignas(int) [[]] __attribute__(()) int e; // expected-error {{an attribute list cannot appear here}}
+};
+
+void fn_with_decl() {
+    __attribute__(()) [[]] alignas(int) int a; // expected-error {{an attribute list cannot appear here}}
+    __attribute__(()) alignas(int) [[]] int b; // expected-error {{an attribute list cannot appear here}}
+    __attribute__(()) alignas(int) int c; // expected-none
+    [[]] __attribute__(()) alignas(int) int d; // expected-none
+    alignas(int) [[]] __attribute__(()) int e; // expected-error {{an attribute list cannot appear here}}
+}

clang/test/Parser/cxx0x-attributes.cpp

@@ -72,6 +72,30 @@ namespace test_misplacement {
 [[]] enum  E2 { }; //expected-error{{misplaced attributes}}
 }
 
+__attribute__(()) alignas(int) int xx; // expected-none
+__attribute__(()) alignas(int) [[]] int yy; // expected-none
+[[]] __attribute__(()) alignas(int) int zz; // expected-none
+alignas(int) [[]] __attribute__(()) int aa; // expected-none
+[[]] alignas(int)  __attribute__(()) int bb; // expected-none
+__attribute__(()) [[]] alignas(int) int cc; // expected-none
+
+class C1 {
+  __attribute__(()) alignas(int) int x; // expected-none
+  __attribute__(()) alignas(int) [[]] int y; // expected-none
+  [[]] __attribute__(()) alignas(int) int z; // expected-none
+  alignas(int) [[]] __attribute__(()) int a; // expected-none
+  [[]] alignas(int)  __attribute__(()) int b; // expected-none
+  __attribute__(()) [[]] alignas(int) int c; // expected-none
+};
+
+void fn_with_decl() {
+  __attribute__(()) alignas(int) int x; // expected-none
+  __attribute__(()) alignas(int) [[]] int y; // expected-none
+  [[]] __attribute__(()) alignas(int) int z; // expected-none
+  alignas(int) [[]] __attribute__(()) int a; // expected-none
+  [[]] alignas(int)  __attribute__(()) int b; // expected-none
+  __attribute__(()) [[]] alignas(int) int c; // expected-none
+}
 // Checks attributes placed at wrong syntactic locations of class specifiers.
 class [[]] [[]]
   attr_after_class_name_decl [[]] [[]]; // expected-error {{an attribute list cannot appear here}}

clang/test/SemaCUDA/cuda-attr-order.cu

@@ -0,0 +1,15 @@
+// Verify that we can parse a simple CUDA file with different attributes order.
+// RUN: %clang_cc1 "-triple" "nvptx-nvidia-cuda"  -fsyntax-only -verify %s
+// expected-no-diagnostics
+#include "Inputs/cuda.h"
+
+struct alignas(16) float4 {
+    float x, y, z, w;
+};
+
+__attribute__((device)) float func() {
+    __shared__ alignas(alignof(float4)) float As[4][4];  // Both combinations
+    alignas(alignof(float4)) __shared__  float Bs[4][4]; // must be legal
+
+    return As[0][0] + Bs[0][0];
+}

clang/test/SemaCXX/warn-thread-safety-analysis.cpp

@@ -2434,10 +2434,10 @@ class Foo {
 namespace WarnNoDecl {
 
 class Foo {
-  void foo(int a);  __attribute__(( // \
-    // expected-warning {{declaration does not declare anything}}
-    exclusive_locks_required(a))); // \
-    // expected-warning {{attribute exclusive_locks_required ignored}}
+  void foo(int a);  __attribute__((
+    exclusive_locks_required(a))); // expected-warning {{declaration does not declare anything}} \
+                                   // expected-warning {{attribute exclusive_locks_required ignored}}
+
 };
 
 } // end namespace WarnNoDecl