Re: [patch, libgfortran] Fix numerous formatting bugs

[Jerry DeLisle <jvdelisle at frontier dot com>]

On 04/25/2011 03:48 AM, Janne Blomqvist wrote:
> On Sun, Apr 24, 2011 at 23:32, Jerry DeLisle<jvdelisle@frontier.com>  wrote:
> > The final solution to 48602 I want to do as a second phase to this. The
> > second phase will attempt to avoid floating point comparisons which are
> > sensitive to optimizations and or printf behavior.
>
> Sounds like a good idea. I think it should be possible to modify the
> algorithm to just count decimal places with integer arithmetic.
>
> > Regression tested on x86-64. I do have some concern that the test cases
> > modified may have issues on other platforms because we have increased the
> > default precision on some reals.  If this happens we should be able to
> > adjust test cases by not using default formatting.
>
> Or xfail the testcases in question on those targets; I think it makes
> sense to assume IEEE 754 hardware and a snprintf() capable of correct
> rounding as the baseline.
>
> Now, for one of the testcase changes:
>
> --- gcc/testsuite/gfortran.dg/char4_iunit_1.f03	(revision 172909)
> +++ gcc/testsuite/gfortran.dg/char4_iunit_1.f03	(working copy)
> @@ -24,11 +24,11 @@ program char4_iunit_1
>     write(string, *) .true., .false. , .true.
>     if (string .ne. 4_" T F T                                    ") call abort
>     write(string, *) 1.2345e-06, 4.2846e+10_8
> -  if (string .ne. 4_"  1.23450002E-06   42846000000.000000     ") call abort
> +  if (string .ne. 4_"  1.234500019E-06   42846000000.000000    ") call abort
>
> This looks wrong. For correctly rounded REAL(4) output, we need 9
> significant digits, but here we print 10.

Well, I bumped it up for defaults based on pr48488 comment #2 shown below. Have 
I misinterpreted? Maybe what we want is w=16, d=8?

Jerry

Index: libgfortran/io/write.c
===================================================================
--- libgfortran/io/write.c	(revision 172909)
+++ libgfortran/io/write.c	(working copy)
@@ -1432,8 +1432,8 @@ set_fnode_default (st_parameter_dt *dtp, fnode *f,
   switch (length)
     {
     case 4:
-      f->u.real.w = 15;
-      f->u.real.d = 8;
+      f->u.real.w = 16;
+      f->u.real.d = 9;
       f->u.real.e = 2;
       break;
     case 8:
@@ -1442,13 +1442,13 @@ set_fnode_default (st_parameter_dt *dtp, fnode *f,
       f->u.real.e = 3;
       break;
     case 10:
-      f->u.real.w = 29;
-      f->u.real.d = 20;
+      f->u.real.w = 30;
+      f->u.real.d = 21;
       f->u.real.e = 4;
       break;
     case 16:
-      f->u.real.w = 44;
-      f->u.real.d = 35;
+      f->u.real.w = 45;
+      f->u.real.d = 36;
       f->u.real.e = 4;
       break;
     default: