https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93567
--- Comment #4 from Dominique d'Humieres <dominiq at lps dot ens.fr> --- The patch in comment 3 broke gfortran.dg/round_3.f08. The following should work --- ../_clean/libgfortran/io/write_float.def 2020-06-13 03:11:55.000000000 +0200 +++ libgfortran/io/write_float.def 2020-07-21 00:37:24.000000000 +0200 @@ -1004,7 +1004,11 @@ determine_en_precision (st_parameter_dt exp_d = calculate_exp_ ## x (d);\ r_sc = (1 - r / exp_d);\ temp = 0.1 * r_sc;\ - if ((m > 0.0 && ((m < temp) || (r >= (exp_d - m))))\ + if ((m > 0.0 && ((m < temp) || (r == 0.5 && r >= (exp_d - m))\ + || (r == 1 && !sign_bit && 1 > (exp_d - m))\ + || (r == 1 && sign_bit && 0 >= (exp_d - m))\ + || (r == 0 && !sign_bit && 0 >= (exp_d - m))\ + || (r ==0 && sign_bit && 1 > (exp_d - m))))\ || ((m == 0.0) && !(compile_options.allow_std\ & (GFC_STD_F2003 | GFC_STD_F2008)))\ || d == 0)\