Implement C++11 [dcl.align]p1 and C11 6.7.5/2 rules for alignas and _Alignas.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173779 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 56 insertions, 10 deletions

diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 438c6f8cf5..20d8f711ae 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -3890,6 +3890,9 @@ bool Parser::isDeclarationSpecifier(bool DisambiguatingWithExpression) {
   case tok::kw_explicit:
   case tok::kw__Noreturn:
 
+    // alignment-specifier
+  case tok::kw__Alignas:
+
     // friend keyword.
   case tok::kw_friend:
 
diff --git a/lib/Parse/ParseStmt.cpp b/lib/Parse/ParseStmt.cpp
index 0a1eccaa76..8b026e859f 100644
--- a/lib/Parse/ParseStmt.cpp
+++ b/lib/Parse/ParseStmt.cpp
@@ -2156,14 +2156,13 @@ StmtResult Parser::ParseCXXTryBlockCommon(SourceLocation TryLoc, bool FnTry) {
 
 /// ParseCXXCatchBlock - Parse a C++ catch block, called handler in the standard
 ///
-///       handler:
-///         'catch' '(' exception-declaration ')' compound-statement
+///   handler:
+///     'catch' '(' exception-declaration ')' compound-statement
 ///
-///       exception-declaration:
-///         type-specifier-seq declarator
-///         type-specifier-seq abstract-declarator
-///         type-specifier-seq
-///         '...'
+///   exception-declaration:
+///     attribute-specifier-seq[opt] type-specifier-seq declarator
+///     attribute-specifier-seq[opt] type-specifier-seq abstract-declarator[opt]
+///     '...'
 ///
 StmtResult Parser::ParseCXXCatchBlock(bool FnCatch) {
   assert(Tok.is(tok::kw_catch) && "Expected 'catch'");
@@ -2184,9 +2183,15 @@ StmtResult Parser::ParseCXXCatchBlock(bool FnCatch) {
   // without default arguments.
   Decl *ExceptionDecl = 0;
   if (Tok.isNot(tok::ellipsis)) {
+    ParsedAttributesWithRange Attributes(AttrFactory);
+    MaybeParseCXX11Attributes(Attributes);
+
     DeclSpec DS(AttrFactory);
+    DS.takeAttributesFrom(Attributes);
+
     if (ParseCXXTypeSpecifierSeq(DS))
       return StmtError();
+
     Declarator ExDecl(DS, Declarator::CXXCatchContext);
     ParseDeclarator(ExDecl);
     ExceptionDecl = Actions.ActOnExceptionDeclarator(getCurScope(), ExDecl);
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 0e51ba3ba3..01a3505cf7 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -3272,9 +3272,47 @@ static void handleAlignedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
     return;
   }
 
-  //FIXME: The C++0x version of this attribute has more limited applicabilty
-  //       than GNU's, and should error out when it is used to specify a
-  //       weaker alignment, rather than being silently ignored.
+  // C++11 alignas(...) and C11 _Alignas(...) have additional requirements.
+  // FIXME: Use a more reliable mechanism to determine how the attribute was
+  //        spelled.
+  if (Attr.isKeywordAttribute()) {
+    // C++11 [dcl.align]p1:
+    //   An alignment-specifier may be applied to a variable or to a class
+    //   data member, but it shall not be applied to a bit-field, a function
+    //   parameter, the formal parameter of a catch clause, or a variable
+    //   declared with the register storage class specifier. An
+    //   alignment-specifier may also be applied to the declaration of a class
+    //   or enumeration type.
+    // C11 6.7.5/2:
+    //   An alignment attribute shall not be specified in a declaration of
+    //   a typedef, or a bit-field, or a function, or a parameter, or an
+    //   object declared with the register storage-class specifier.
+    int DiagKind = -1;
+    if (isa<ParmVarDecl>(D)) {
+      DiagKind = 0;
+    } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
+      if (VD->getStorageClass() == SC_Register)
+        DiagKind = 1;
+      if (VD->isExceptionVariable())
+        DiagKind = 2;
+    } else if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
+      if (FD->isBitField())
+        DiagKind = 3;
+    } else if (!isa<TagDecl>(D)) {
+      S.Diag(Attr.getLoc(), diag::err_attribute_wrong_decl_type)
+        << Attr.getName() << ExpectedVariableFunctionOrTag;
+      return;
+    }
+    if (DiagKind != -1) {
+      S.Diag(Attr.getLoc(), diag::err_alignas_attribute_wrong_decl_type)
+        << Attr.getName() << DiagKind;
+      return;
+    }
+  }
+
+  // FIXME: The C++11 version of this attribute should error out when it is
+  //        used to specify a weaker alignment, rather than being silently
+  //        ignored.
 
   if (Attr.getNumArgs() == 0) {
     D->addAttr(::new (S.Context) AlignedAttr(Attr.getRange(), S.Context,