fix duplicate symbols for EmptyPayload

diff --git a/include/deal.II/lac/linear_operator.h b/include/deal.II/lac/linear_operator.h
index 0fbfec3161bc65d68d72d6e464d9919434c74e01..86f45d6ee53332287d6034dda8e50ffa7d0b2c2e 100644 (file)
--- a/include/deal.II/lac/linear_operator.h
+++ b/include/deal.II/lac/linear_operator.h
@@ -935,6 +935,7 @@ namespace internal
     * Operator that returns a payload configured to support the
     * addition of two LinearOperators
     */
+    inline
     EmptyPayload operator+(const EmptyPayload &,
                            const EmptyPayload &)
     {
@@ -945,6 +946,7 @@ namespace internal
     * Operator that returns a payload configured to support the
     * multiplication of two LinearOperators
     */
+    inline
     EmptyPayload operator*(const EmptyPayload &,
                            const EmptyPayload &)
     {