Don't add attributes for "#pragma pack" and friends to tag declarations which

are not definitions. This follows the behavior of both gcc and earlier
versions of clang. Regression from r156531.  <rdar://problem/12048621>.

llvm-svn: 161523

clang/lib/Sema/SemaDecl.cpp

@@ -8807,9 +8807,10 @@ CreateNewDecl:
     // many points during the parsing of a struct declaration (because
     // the #pragma tokens are effectively skipped over during the
     // parsing of the struct).
-    AddAlignmentAttributesForRecord(RD);
-    
-    AddMsStructLayoutForRecord(RD);
+    if (TUK == TUK_Definition) {
+      AddAlignmentAttributesForRecord(RD);
+      AddMsStructLayoutForRecord(RD);
+    }
   }
 
   if (ModulePrivateLoc.isValid()) {

clang/lib/Sema/SemaTemplate.cpp

@@ -1064,8 +1064,10 @@ Sema::CheckClassTemplate(Scope *S, unsigned TagSpec, TagUseKind TUK,
 
   // Add alignment attributes if necessary; these attributes are checked when
   // the ASTContext lays out the structure.
-  AddAlignmentAttributesForRecord(NewClass);
-  AddMsStructLayoutForRecord(NewClass);
+  if (TUK == TUK_Definition) {
+    AddAlignmentAttributesForRecord(NewClass);
+    AddMsStructLayoutForRecord(NewClass);
+  }
 
   ClassTemplateDecl *NewTemplate
     = ClassTemplateDecl::Create(Context, SemanticContext, NameLoc,

clang/test/Sema/pragma-pack-6.c

@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -triple i686-apple-darwin9 %s -fsyntax-only -verify
+
+// Pragma pack handling with tag declarations
+
+struct X;
+
+#pragma pack(2)
+struct X { int x; };
+struct Y;
+#pragma pack()
+
+struct Y { int y; };
+
+extern int check[__alignof(struct X) == 2 ? 1 : -1];
+extern int check[__alignof(struct Y) == 4 ? 1 : -1];
+