[Bug libc/303] New: scanf into single rounds in 2.3.3 (truncates in 2.3.1)

["d dot bullivant at auckland dot ac dot nz" <sourceware-bugzilla at sources dot redhat dot com>]

When reading into a single with %f, scanf now rounds (2.3.3) whereas it used to
truncate (2.3.1) - see program below.

Could you please confirm that this is an intentional change.

*******************************************************************************
FILE : scanf_double.c

LAST MODIFIED : 5 August 2004

DESCRIPTION:
Code for testing reading doubles into singles.

BUILD:
gcc scanf_double.c -o scanf_double

OUTPUT:
glibc-2.3.1
single 5 7e2fe
double 5 7e2fe81f74638
difference 1.93664e-06

glibc-2.3.3
single 5 7e2ff
double 5 7e2fe81f74638
difference -1.87805e-06
==============================================================================*/

#include <ieee754.h>

main(int argc,char **argv)
{
        char *string_double="0.3397167399474852E+02";
        double d;
        float f;
        union ieee754_double *d_ptr;
        union ieee754_float *f_ptr;

        d_ptr=(union ieee754_double *)&d;
        f_ptr=(union ieee754_float *)&f;
        sscanf(string_double,"%f",&f);
        sscanf(string_double,"%lf",&d);
        printf("single %lx
%lx\n",(f_ptr->ieee).exponent-127,(f_ptr->ieee).mantissa);
        printf("double %lx %llx\n",(d_ptr->ieee).exponent-1023,
                ((long long unsigned)((d_ptr->ieee).mantissa0)*0x100000000ll+
                (long long unsigned)((d_ptr->ieee).mantissa1))*0x8ll);
        printf("difference %g\n",d-(double)f);
}

-- 
           Summary: scanf into single rounds in 2.3.3 (truncates in 2.3.1)
           Product: glibc
           Version: 2.3.3
            Status: NEW
          Severity: minor
          Priority: P2
         Component: libc
        AssignedTo: gotom at debian dot or dot jp
        ReportedBy: d dot bullivant at auckland dot ac dot nz
                CC: glibc-bugs at sources dot redhat dot com


http://sources.redhat.com/bugzilla/show_bug.cgi?id=303

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