CVS commit: src/tests/lib/libc/stdio

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Thu May  9 22:38:29 UTC 2024

Modified Files:
        src/tests/lib/libc/stdio: t_printf.c

Log Message:
tests/lib/libc/stdio/t_printf: Fix another rounding error.

Noted by kre.

This doesn't break a passing test or fix a failed test, at least on
x86 -- our printf produces `0x1.533p+3' for the double case and
`0xa.99ap+0' for the long double case.  But of the hexadecimal number
literals that that start with 0x5 having three hexadigits to the
right of the fractional point, 0x5.4cdp+1 closest to the IEEE 754
binary64, VAX D, x86 extended precision, and IEEE 754 binary128
floating-point numbers closest to 10.6.

The reason is that the number 10.6 (or the nearest floating-point
number in any format with enough precision) is:

101.0100 1100 1100|1100... * 2^1 = 0x5.4cc|c...p+1

If we round at the vertical bar to the _nearest_ output with three
hexadigits of precision, the result is:

101.0100 1100 1101 * 2^1 = 0x5.4cdp+1


To generate a diff of this commit:
cvs rdiff -u -r1.15 -r1.16 src/tests/lib/libc/stdio/t_printf.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.