[Bug libfortran/59836] New: Wrong outputs with rounding formats for some values.
dominiq at lps dot ens.fr
gcc-bugzilla@gcc.gnu.org
Wed Jan 15 22:24:00 GMT 2014
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59836
Bug ID: 59836
Summary: Wrong outputs with rounding formats for some values.
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libfortran
Assignee: unassigned at gcc dot gnu.org
Reporter: dominiq at lps dot ens.fr
CC: jvdelisle at gcc dot gnu.org
This is a split off pr59774 comment 9. The code
print "(ru,g45.3)", 891.1
print "(rd,g45.3)", -891.1
end
compiled with trunk (r206559) gives the output
9.
-9.
I have also found that the code
print '(RU,F2.0)', 0.6
print '(RD,F3.0)', -0.6
end
gives
7.
-7.
Both problems occur because the Fw.d format is not properly handled when d==0.
The following patch fixes both problems
--- ../_clean/libgfortran/io/write_float.def 2014-01-04 15:51:53.000000000
+0100
+++ libgfortran/io/write_float.def 2014-01-15 22:22:17.000000000 +0100
@@ -373,7 +373,7 @@ output_float (st_parameter_dt *dtp, cons
updown:
rchar = '0';
- if (w > 0 && d == 0 && p == 0)
+ if (ft != FMT_F && nbefore == 0 && w > 0 && d == 0 && p == 0)
nbefore = 1;
/* Scan for trailing zeros to see if we really need to round it. */
for(i = nbefore + nafter; i < ndigits; i++)
@@ -386,13 +386,14 @@ output_float (st_parameter_dt *dtp, cons
do_rnd:
if (nbefore + nafter == 0)
+ /* Handle the case Fw.0 and value < 1.0 */
{
ndigits = 0;
if (nzero_real == d && digits[0] >= rchar)
{
/* We rounded to zero but shouldn't have */
- nzero--;
- nafter = 1;
+ nbefore = 1;
+ digits--;
digits[0] = '1';
ndigits = 1;
}
The first patch handles the first problem by restricting the test to the E*
formats and the second one fixes the way Fw.0 handles values < 1.0 (yes, I have
seen the formatting issue for the line digits--. I'll fix it when I'll submit
the patch).
AFAICT the line nzero--; does not seem necessary, but I don't know why.
With the patch the first test gives
892.
-892.
and the second
1.
-1.
and I did not see any regression when retesting with it.
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