Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -75,6 +75,7 @@
 def GNUDesignator : DiagGroup<"gnu-designator">;
 def GNUStringLiteralOperatorTemplate :
   DiagGroup<"gnu-string-literal-operator-template">;
+def UnavailableTemplate : DiagGroup<"unavailable-template">;
 
 def DeleteIncomplete : DiagGroup<"delete-incomplete">;
 def DeleteNonVirtualDtor : DiagGroup<"delete-non-virtual-dtor">;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -3821,7 +3821,12 @@
   "in instantiation of template type alias %0 requested here">;
 def note_template_exception_spec_instantiation_here : Note<
   "in instantiation of exception specification for %0 requested here">;
-  
+
+def warn_var_template_missing : Warning<"instantiation of %q0 required here, "
+  "but corresponding template is not found">, InGroup<UnavailableTemplate>;
+def note_inst_declaration_hint : Note<"add an explicit instantiation declaration "
+  "to suppress this warning if %q0 is explicitly instantiated in another "
+  "translation unit">;
 def note_default_arg_instantiation_here : Note<
   "in instantiation of default argument for '%0' required here">;
 def note_default_function_arg_instantiation_here : Note<
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -7128,7 +7128,8 @@
       const MultiLevelTemplateArgumentList &TemplateArgs);
   void InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
                                      VarDecl *Var, bool Recursive = false,
-                                     bool DefinitionRequired = false);
+                                     bool DefinitionRequired = false,
+                                     bool AtEndOfTU = false);
   void InstantiateStaticDataMemberDefinition(
                                      SourceLocation PointOfInstantiation,
                                      VarDecl *Var,
Index: lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3768,7 +3768,7 @@
 
 void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
                                          VarDecl *Var, bool Recursive,
-                                         bool DefinitionRequired) {
+                                      bool DefinitionRequired, bool AtEndOfTU) {
   if (Var->isInvalidDecl())
     return;
 
@@ -3900,6 +3900,14 @@
                  == TSK_ExplicitInstantiationDefinition) {
       PendingInstantiations.push_back(
         std::make_pair(Var, PointOfInstantiation));
+    } else if (Var->getTemplateSpecializationKind()
+                 == TSK_ImplicitInstantiation) {
+      // Warn about missing definition at the end of translation unit.
+      if (AtEndOfTU && !getDiagnostics().hasErrorOccurred()) {
+        Diag(PointOfInstantiation, diag::warn_var_template_missing)
+          << Var;
+        Diag(PointOfInstantiation, diag::note_inst_declaration_hint) << Var;
+      }
     }
 
     return;
@@ -4710,7 +4718,7 @@
     // Instantiate static data member definitions or variable template
     // specializations.
     InstantiateVariableDefinition(/*FIXME:*/ Inst.second, Var, true,
-                                  DefinitionRequired);
+                                  DefinitionRequired, true);
   }
 }
 
Index: test/CXX/temp/temp.decls/temp.mem/p1.cpp
===================================================================
--- test/CXX/temp/temp.decls/temp.mem/p1.cpp
+++ test/CXX/temp/temp.decls/temp.mem/p1.cpp
@@ -10,6 +10,7 @@
     }
   };
 };
+extern template bool A<bool>::cond;
 
 int foo() {
   A<bool>::cond = true;
Index: test/OpenMP/parallel_ast_print.cpp
===================================================================
--- test/OpenMP/parallel_ast_print.cpp
+++ test/OpenMP/parallel_ast_print.cpp
@@ -171,4 +171,7 @@
   }
 }
 
+template<typename T>
+T S<T>::TS = 0;
+
 #endif
Index: test/OpenMP/parallel_sections_ast_print.cpp
===================================================================
--- test/OpenMP/parallel_sections_ast_print.cpp
+++ test/OpenMP/parallel_sections_ast_print.cpp
@@ -141,4 +141,7 @@
   return tmain<int, 5>(b, &b) + tmain<long, 1>(x, &x);
 }
 
+template<typename T>
+T S<T>::TS = 0;
+
 #endif
Index: test/OpenMP/task_ast_print.cpp
===================================================================
--- test/OpenMP/task_ast_print.cpp
+++ test/OpenMP/task_ast_print.cpp
@@ -149,4 +149,7 @@
   return tmain<int, 5>(b, &b) + tmain<long, 1>(x, &x);
 }
 
+extern template int S<int>::TS;
+extern template long S<long>::TS;
+
 #endif
Index: test/OpenMP/teams_ast_print.cpp
===================================================================
--- test/OpenMP/teams_ast_print.cpp
+++ test/OpenMP/teams_ast_print.cpp
@@ -109,4 +109,6 @@
   return tmain<int, 5>(b, &b) + tmain<long, 1>(x, &x);
 }
 
+extern template int S<int>::TS;
+extern template long S<long>::TS;
 #endif
Index: test/OpenMP/threadprivate_ast_print.cpp
===================================================================
--- test/OpenMP/threadprivate_ast_print.cpp
+++ test/OpenMP/threadprivate_ast_print.cpp
@@ -69,4 +69,5 @@
   return (foo<int>());
 }
 
+extern template int ST<int>::m;
 #endif
Index: test/SemaCXX/PR10177.cpp
===================================================================
--- test/SemaCXX/PR10177.cpp
+++ test/SemaCXX/PR10177.cpp
@@ -54,6 +54,7 @@
 
 namespace { template<typename> extern int n; }
 template<typename T> int g() { return n<int>; }
+namespace { extern template int n<int>; }
 
 #endif
 
Index: test/SemaCXX/undefined-internal.cpp
===================================================================
--- test/SemaCXX/undefined-internal.cpp
+++ test/SemaCXX/undefined-internal.cpp
@@ -82,6 +82,7 @@
     static int var; // expected-warning {{variable 'test5::B<test5::(anonymous namespace)::A>::var' has internal linkage but is not defined}}
     static void foo(); // expected-warning {{function 'test5::B<test5::(anonymous namespace)::A>::foo' has internal linkage but is not defined}}
   };
+  extern template int B<A>::var;
 
   void test() {
     B<A>::var = 0; // expected-note {{used here}}
Index: test/SemaTemplate/unavailable-var-template.cpp
===================================================================
--- /dev/null
+++ test/SemaTemplate/unavailable-var-template.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+template <class T> struct Foo {
+  static char s_bar;
+  static char s_bar2;
+};
+
+extern template char Foo<int>::s_bar2;
+
+char baz(char x) {
+  if (x == '.')
+    return Foo<int>::s_bar2;
+  return Foo<int>::s_bar; // expected-warning{{instantiation of 'Foo<int>::s_bar' required here, but corresponding template is not found}}
+                          // expected-note@-1{{add an explicit instantiation declaration to suppress this warning if 'Foo<int>::s_bar' is explicitly instantiated in another translation unit}}
+}