diff -ru magma-2.3.0/testing/testings.h magma-2.3.0-patched/testing/testings.h
--- magma-2.3.0/testing/testings.h	2017-11-14 21:34:00.000000000 -0800
+++ magma-2.3.0-patched/testing/testings.h	2018-03-23 20:41:16.459934643 -0700
@@ -269,4 +269,20 @@
     typename blas::traits<FloatT>::real_t* sigma,
     FloatT* A, magma_int_t lda );
 
+// This overload for the case sigma = nullptr is a workaround for an issue
+// when building with gcc 4.8.5. This is not an issue with gcc 4.9.2.
+template< typename FloatT >
+void magma_generate_matrix(
+    magma_opts& opts,
+    magma_int_t m, magma_int_t n,
+    std::nullptr_t sigma,
+    FloatT* A, magma_int_t lda )
+{
+    magma_generate_matrix<FloatT>(
+        opts,
+        m, n,
+        (typename blas::traits<FloatT>::real_t*) sigma,
+        A, lda );
+}
+
 #endif /* TESTINGS_H */