diff -Nrup a/m4/mathfunc.m4 b/m4/mathfunc.m4
--- a/m4/mathfunc.m4	2016-12-14 17:03:33.000000000 -0700
+++ b/m4/mathfunc.m4	2020-01-06 19:48:46.684158282 -0700
@@ -60,7 +60,7 @@ AC_DEFUN([gl_MATHFUNC],
              #endif
              #include <math.h>
              $4
-             $2 (*funcptr) $3 = ]func[;
+             __attribute__ ((used)) $2 (*funcptr) $3 = ]func[;
              int i_ret;
              float f_ret;
              double d_ret;
@@ -85,7 +85,7 @@ AC_DEFUN([gl_MATHFUNC],
                #endif
                #include <math.h>
                $4
-               $2 (*funcptr) $3 = ]func[;
+               __attribute__ ((used)) $2 (*funcptr) $3 = ]func[;
                int i_ret;
                float f_ret;
                double d_ret;