PR90374 Zero width format specifiers.

	PR libfortran/90374
	* io/format.c (parse_format_list): Zero width not allowed with
	FMT_D.
	* io/write_float.def (build_float_string): Include range of
	higher exponent values that require wider width.

libgfortran/ChangeLog

+2020-01-17  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
+
+	PR libfortran/90374
+	* io/format.c (parse_format_list): Zero width not allowed with
+	FMT_D.
+	* io/write_float.def (build_float_string): Include range of
+	higher exponent values that require wider width.
+
 2020-01-01  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR libfortran/90374

libgfortran/io/format.c

@@ -954,7 +954,9 @@ parse_format_list (st_parameter_dt *dtp, bool *seen_dd)
 	    }
 	  tail->u.real.d = fmt->value;
 	  
-	  /* Look for optional exponent */
+	  /* Look for optional exponent, not allowed for FMT_D */
+	  if (t == FMT_D)
+	    break;
 	  u = format_lex (fmt);
 	  if (u != FMT_E)
 	    fmt->saved_token = u;

libgfortran/io/write_float.def

@@ -497,7 +497,9 @@ build_float_string (st_parameter_dt *dtp, const fnode *f, char *buffer,
       else if (f->u.real.e == 0)
 	{
 	  /* Zero width specified, no leading zeros in exponent  */
-	  if (e > 99 || e < -99)
+	  if (e > 999 || e < -999)
+	    edigits = 6;
+	  else if (e > 99 || e < -99)
 	    edigits = 5;
 	  else if (e > 9 || e < -9)
 	    edigits = 4;