3 files changed, 29 insertions, 1 deletions
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 07368790372..3a967c6fdc3 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1937,7 +1937,13 @@ CodeGenModule::GetLLVMLinkageVarDefinition(const VarDecl *D,
     return llvm::Function::DLLImportLinkage;
   else if (D->hasAttr<DLLExportAttr>())
     return llvm::Function::DLLExportLinkage;
-  else if (D->hasAttr<WeakAttr>()) {
+  else if (D->hasAttr<SelectAnyAttr>()) {
+    // selectany symbols are externally visible, so use weak instead of
+    // linkonce.  MSVC optimizes away references to const selectany globals, so
+    // all definitions should be the same and ODR linkage should be used.
+    // http://msdn.microsoft.com/en-us/library/5tkz6s71.aspx
+    return llvm::GlobalVariable::WeakODRLinkage;
+  } else if (D->hasAttr<WeakAttr>()) {
     if (GV->isConstant())
       return llvm::GlobalVariable::WeakODRLinkage;
     else
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 885e8759422..50951a03f0c 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4636,6 +4636,15 @@ static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
       ND.dropAttr<WeakRefAttr>();
     }
   }
+
+  // 'selectany' only applies to externally visible varable declarations.
+  // It does not apply to functions.
+  if (SelectAnyAttr *Attr = ND.getAttr<SelectAnyAttr>()) {
+    if (isa<FunctionDecl>(ND) || !ND.isExternallyVisible()) {
+      S.Diag(Attr->getLocation(), diag::err_attribute_selectany_non_extern_data);
+      ND.dropAttr<SelectAnyAttr>();
+    }
+  }
 }
 
 /// Given that we are within the definition of the given function,
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index c365bfc508c..627bc3d3649 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -4718,6 +4718,16 @@ static void handleForceInlineAttr(Sema &S, Decl *D, const AttributeList &Attr) {
                              Attr.getAttributeSpellingListIndex()));
 }
 
+static void handleSelectAnyAttr(Sema &S, Decl *D, const AttributeList &Attr) {
+  if (!checkMicrosoftExt(S, Attr))
+    return;
+  // Check linkage after possibly merging declaratinos.  See
+  // checkAttributesAfterMerging().
+  D->addAttr(::new (S.Context)
+             SelectAnyAttr(Attr.getRange(), S.Context,
+                           Attr.getAttributeSpellingListIndex()));
+}
+
 //===----------------------------------------------------------------------===//
 // Top Level Sema Entry Points
 //===----------------------------------------------------------------------===//
@@ -4944,6 +4954,9 @@ static void ProcessInheritableDeclAttr(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_ForceInline:
     handleForceInlineAttr(S, D, Attr);
     break;
+  case AttributeList::AT_SelectAny:
+    handleSelectAnyAttr(S, D, Attr);
+    break;
 
   // Thread safety attributes:
   case AttributeList::AT_AssertExclusiveLock: