diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index bd461f4597a1..37f277da52a3 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2074,6 +2074,8 @@ def err_attribute_weak_static : Error<
   "weak declaration cannot have internal linkage">;
 def err_attribute_selectany_non_extern_data : Error<
   "'selectany' can only be applied to data items with external linkage">;
+def err_attribute_dll_not_extern : Error<
+  "%q0 must have external linkage when declared %q1">;
 def warn_attribute_invalid_on_definition : Warning<
   "'%0' attribute cannot be specified on a definition">,
   InGroup<IgnoredAttributes>;
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 26f8b2587fdd..9d7f13cdd789 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4843,6 +4843,22 @@ static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
       ND.dropAttr<SelectAnyAttr>();
     }
   }
+
+  // dll attributes require external linkage.
+  if (const DLLImportAttr *Attr = ND.getAttr<DLLImportAttr>()) {
+    if (!ND.isExternallyVisible()) {
+      S.Diag(ND.getLocation(), diag::err_attribute_dll_not_extern)
+        << &ND << Attr;
+      ND.setInvalidDecl();
+    }
+  }
+  if (const DLLExportAttr *Attr = ND.getAttr<DLLExportAttr>()) {
+    if (!ND.isExternallyVisible()) {
+      S.Diag(ND.getLocation(), diag::err_attribute_dll_not_extern)
+        << &ND << Attr;
+      ND.setInvalidDecl();
+    }
+  }
 }
 
 static void checkDLLAttributeRedeclaration(Sema &S, NamedDecl *OldDecl,
diff --git a/clang/test/Sema/dllexport.c b/clang/test/Sema/dllexport.c
index 675bd492f856..8a71e5d7251e 100644
--- a/clang/test/Sema/dllexport.c
+++ b/clang/test/Sema/dllexport.c
@@ -41,9 +41,15 @@ __declspec(dllexport) extern int GlobalRedecl2;
                       extern int GlobalRedecl3; // expected-note{{previous declaration is here}}
 __declspec(dllexport) extern int GlobalRedecl3; // expected-error{{redeclaration of 'GlobalRedecl3' cannot add 'dllexport' attribute}}
 
+// External linkage is required.
+__declspec(dllexport) static int StaticGlobal; // expected-error{{'StaticGlobal' must have external linkage when declared 'dllexport'}}
+
 // Export in local scope.
 void functionScope() {
+  __declspec(dllexport)        int LocalVarDecl; // expected-error{{'LocalVarDecl' must have external linkage when declared 'dllexport'}}
+  __declspec(dllexport)        int LocalVarDef = 1; // expected-error{{'LocalVarDef' must have external linkage when declared 'dllexport'}}
   __declspec(dllexport) extern int ExternLocalVarDecl;
+  __declspec(dllexport) static int StaticLocalVar; // expected-error{{'StaticLocalVar' must have external linkage when declared 'dllexport'}}
 }
 
 
@@ -82,6 +88,9 @@ __declspec(dllexport) void redecl3();
                       void redecl4(); // expected-note{{previous declaration is here}}
 __declspec(dllexport) void redecl4(); // expected-error{{redeclaration of 'redecl4' cannot add 'dllexport' attribute}}
 
+// External linkage is required.
+__declspec(dllexport) static int staticFunc(); // expected-error{{'staticFunc' must have external linkage when declared 'dllexport'}}
+
 
 
 //===----------------------------------------------------------------------===//
diff --git a/clang/test/Sema/dllimport.c b/clang/test/Sema/dllimport.c
index 46031173cd2d..a4982940c65a 100644
--- a/clang/test/Sema/dllimport.c
+++ b/clang/test/Sema/dllimport.c
@@ -64,6 +64,9 @@ __declspec(dllimport) extern int GlobalRedecl3; // expected-note{{previous decla
                       extern int GlobalRedecl4; // expected-note{{previous declaration is here}}
 __declspec(dllimport) extern int GlobalRedecl4; // expected-error{{redeclaration of 'GlobalRedecl4' cannot add 'dllimport' attribute}}
 
+// External linkage is required.
+__declspec(dllimport) static int StaticGlobal; // expected-error{{'StaticGlobal' must have external linkage when declared 'dllimport'}}
+
 // Import in local scope.
 __declspec(dllimport) float LocalRedecl1; // expected-note{{previous definition is here}}
 __declspec(dllimport) float LocalRedecl2; // expected-note{{previous definition is here}}
@@ -77,6 +80,7 @@ void functionScope() {
   __declspec(dllimport)        int LocalVarDef = 1; // expected-error{{definition of dllimport data}}
   __declspec(dllimport) extern int ExternLocalVarDecl;
   __declspec(dllimport) extern int ExternLocalVarDef = 1; // expected-error{{definition of dllimport data}}
+  __declspec(dllimport) static int StaticLocalVar; // expected-error{{'StaticLocalVar' must have external linkage when declared 'dllimport'}}
 }
 
 
@@ -113,3 +117,6 @@ __declspec(dllimport) void redecl3(); // expected-note{{previous declaration is
 
                       void redecl4(); // expected-note{{previous declaration is here}}
 __declspec(dllimport) void redecl4(); // expected-error{{redeclaration of 'redecl4' cannot add 'dllimport' attribute}}
+
+// External linkage is required.
+__declspec(dllimport) static int staticFunc(); // expected-error{{'staticFunc' must have external linkage when declared 'dllimport'}}
diff --git a/clang/test/SemaCXX/dllexport.cpp b/clang/test/SemaCXX/dllexport.cpp
index acbd4ce78f4c..0f4cb5c246d9 100644
--- a/clang/test/SemaCXX/dllexport.cpp
+++ b/clang/test/SemaCXX/dllexport.cpp
@@ -11,6 +11,8 @@ struct ExplicitSpec_Exported {};
 struct ExplicitSpec_Def_Exported {};
 struct ExplicitSpec_InlineDef_Exported {};
 struct ExplicitSpec_NotExported {};
+namespace { struct Internal {}; }
+struct External { int v; };
 
 
 // Invalid usage.
@@ -53,9 +55,21 @@ __declspec(dllexport) extern int GlobalRedecl2;
                       extern int GlobalRedecl3; // expected-note{{previous declaration is here}}
 __declspec(dllexport) extern int GlobalRedecl3; // expected-error{{redeclaration of 'GlobalRedecl3' cannot add 'dllexport' attribute}}
 
+// External linkage is required.
+__declspec(dllexport) static int StaticGlobal; // expected-error{{'StaticGlobal' must have external linkage when declared 'dllexport'}}
+__declspec(dllexport) Internal InternalTypeGlobal; // expected-error{{'InternalTypeGlobal' must have external linkage when declared 'dllexport'}}
+namespace    { __declspec(dllexport) int InternalGlobal; } // expected-error{{'<anonymous namespace>::InternalGlobal' must have external linkage when declared 'dllexport'}}
+namespace ns { __declspec(dllexport) int ExternalGlobal; }
+
+__declspec(dllexport) auto InternalAutoTypeGlobal = Internal(); // expected-error{{'InternalAutoTypeGlobal' must have external linkage when declared 'dllexport'}}
+__declspec(dllexport) auto ExternalAutoTypeGlobal = External();
+
 // Export in local scope.
 void functionScope() {
+  __declspec(dllexport)        int LocalVarDecl; // expected-error{{'LocalVarDecl' must have external linkage when declared 'dllexport'}}
+  __declspec(dllexport)        int LocalVarDef = 1; // expected-error{{'LocalVarDef' must have external linkage when declared 'dllexport'}}
   __declspec(dllexport) extern int ExternLocalVarDecl;
+  __declspec(dllexport) static int StaticLocalVar; // expected-error{{'StaticLocalVar' must have external linkage when declared 'dllexport'}}
 }
 
 
@@ -110,6 +124,12 @@ __declspec(dllexport) void friend3() {} // expected-error{{redeclaration of 'fri
 // Implicit declarations can be redeclared with dllexport.
 __declspec(dllexport) void* operator new(__SIZE_TYPE__ n);
 
+// External linkage is required.
+__declspec(dllexport) static int staticFunc(); // expected-error{{'staticFunc' must have external linkage when declared 'dllexport'}}
+__declspec(dllexport) Internal internalRetFunc(); // expected-error{{'internalRetFunc' must have external linkage when declared 'dllexport'}}
+namespace    { __declspec(dllexport) void internalFunc() {} } // expected-error{{'<anonymous namespace>::internalFunc' must have external linkage when declared 'dllexport'}}
+namespace ns { __declspec(dllexport) void externalFunc() {} }
+
 
 
 //===----------------------------------------------------------------------===//
@@ -143,6 +163,12 @@ template<typename T> __declspec(dllexport) void funcTmplFriend1() {}
 template<typename T>                       void funcTmplFriend2() {}
 template<typename T> __declspec(dllexport) void funcTmplFriend3() {} // expected-error{{redeclaration of 'funcTmplFriend3' cannot add 'dllexport' attribute}}
 
+// External linkage is required.
+template<typename T> __declspec(dllexport) static int staticFuncTmpl(); // expected-error{{'staticFuncTmpl' must have external linkage when declared 'dllexport'}}
+template<typename T> __declspec(dllexport) Internal internalRetFuncTmpl(); // expected-error{{'internalRetFuncTmpl' must have external linkage when declared 'dllexport'}}
+namespace    { template<typename T> __declspec(dllexport) void internalFuncTmpl(); } // expected-error{{'<anonymous namespace>::internalFuncTmpl' must have external linkage when declared 'dllexport'}}
+namespace ns { template<typename T> __declspec(dllexport) void externalFuncTmpl(); }
+
 
 template<typename T> void funcTmpl() {}
 template<typename T> __declspec(dllexport) void exportedFuncTmplDecl();
diff --git a/clang/test/SemaCXX/dllimport.cpp b/clang/test/SemaCXX/dllimport.cpp
index f63943924c69..a96f18b23970 100644
--- a/clang/test/SemaCXX/dllimport.cpp
+++ b/clang/test/SemaCXX/dllimport.cpp
@@ -11,6 +11,7 @@ struct ExplicitSpec_Imported {};
 struct ExplicitSpec_Def_Imported {};
 struct ExplicitSpec_InlineDef_Imported {};
 struct ExplicitSpec_NotImported {};
+namespace { struct Internal {}; }
 
 
 // Invalid usage.
@@ -76,6 +77,15 @@ __declspec(dllimport) extern int GlobalRedecl3; // expected-note{{previous decla
                       extern int GlobalRedecl4; // expected-note{{previous declaration is here}}
 __declspec(dllimport) extern int GlobalRedecl4; // expected-error{{redeclaration of 'GlobalRedecl4' cannot add 'dllimport' attribute}}
 
+// External linkage is required.
+__declspec(dllimport) static int StaticGlobal; // expected-error{{'StaticGlobal' must have external linkage when declared 'dllimport'}}
+__declspec(dllimport) Internal InternalTypeGlobal; // expected-error{{'InternalTypeGlobal' must have external linkage when declared 'dllimport'}}
+namespace    { __declspec(dllimport) int InternalGlobal; } // expected-error{{'<anonymous namespace>::InternalGlobal' must have external linkage when declared 'dllimport'}}
+namespace ns { __declspec(dllimport) int ExternalGlobal; }
+
+__declspec(dllimport) auto InternalAutoTypeGlobal = Internal(); // expected-error{{'InternalAutoTypeGlobal' must have external linkage when declared 'dllimport'}}
+                                                                // expected-error@-1{{definition of dllimport data}}
+
 // Import in local scope.
 __declspec(dllimport) float LocalRedecl1; // expected-note{{previous definition is here}}
 __declspec(dllimport) float LocalRedecl2; // expected-note{{previous definition is here}}
@@ -89,6 +99,7 @@ void functionScope() {
   __declspec(dllimport)        int LocalVarDef = 1; // expected-error{{definition of dllimport data}}
   __declspec(dllimport) extern int ExternLocalVarDecl;
   __declspec(dllimport) extern int ExternLocalVarDef = 1; // expected-error{{definition of dllimport data}}
+  __declspec(dllimport) static int StaticLocalVar; // expected-error{{'StaticLocalVar' must have external linkage when declared 'dllimport'}}
 }
 
 
@@ -144,6 +155,12 @@ __declspec(dllimport) void friend4(); // expected-error{{redeclaration of 'frien
 // Implicit declarations can be redeclared with dllimport.
 __declspec(dllimport) void* operator new(__SIZE_TYPE__ n);
 
+// External linkage is required.
+__declspec(dllimport) static int staticFunc(); // expected-error{{'staticFunc' must have external linkage when declared 'dllimport'}}
+__declspec(dllimport) Internal internalRetFunc(); // expected-error{{'internalRetFunc' must have external linkage when declared 'dllimport'}}
+namespace    { __declspec(dllimport) void internalFunc(); } // expected-error{{'<anonymous namespace>::internalFunc' must have external linkage when declared 'dllimport'}}
+namespace ns { __declspec(dllimport) void externalFunc(); }
+
 
 
 //===----------------------------------------------------------------------===//
@@ -179,6 +196,12 @@ template<typename T>                       void funcTmplFriend2(); // expected-w
 template<typename T>                       void funcTmplFriend3() {} // expected-warning{{'funcTmplFriend3' redeclared without 'dllimport' attribute: previous 'dllimport' ignored}}
 template<typename T> __declspec(dllimport) void funcTmplFriend4(); // expected-error{{redeclaration of 'funcTmplFriend4' cannot add 'dllimport' attribute}}
 
+// External linkage is required.
+template<typename T> __declspec(dllimport) static int staticFuncTmpl(); // expected-error{{'staticFuncTmpl' must have external linkage when declared 'dllimport'}}
+template<typename T> __declspec(dllimport) Internal internalRetFuncTmpl(); // expected-error{{'internalRetFuncTmpl' must have external linkage when declared 'dllimport'}}
+namespace    { template<typename T> __declspec(dllimport) void internalFuncTmpl(); } // expected-error{{'<anonymous namespace>::internalFuncTmpl' must have external linkage when declared 'dllimport'}}
+namespace ns { template<typename T> __declspec(dllimport) void externalFuncTmpl(); }
+
 
 template<typename T> void funcTmpl() {}
 template<typename T> __declspec(dllimport) void importedFuncTmpl();