Public bug reported:
Description:
============
Install a Power 8 machine with Ubuntu LE guest VM.
Then compile and execute the below test case code.
root@ubuntu:~# cat frexpl_example.c
#include <stdio.h>
#include <math.h>
int main(void)
{
union { long double ld; double d[2]; int i[4]; long long l[2]; } x;
int expon;
x.d[0] = 0x1p0;
x.d[1] = -0x1p-106;
printf ("%La %13a %13a 0x%16llx 0x%16llx\n",
x.ld, x.d[0], x.d[1], x.l[0], x.l[1]);
x.ld = frexpl (x.ld, &expon);
printf ("%La %13a %13a 0x%16llx 0x%16llx\n",
x.ld, x.d[0], x.d[1], x.l[0], x.l[1]);
printf ("expon = %d\n", expon);
return 0;
}
root@ubuntu:~# gcc frexpl_example.c -lm
root@ubuntu:~# ./a.out
0x1.ffffffffffffffffffffffffff8p-1 0x1p+0 -0x1p-106 0x3ff0000000000000
0xb950000000000000
0x1.ffffffffffffffffffffffffff8p-2 0x1p-1 -0x1p-107 0x3fe0000000000000
0xb940000000000000
expon = 1
root@ubuntu:~# uname -a
Linux ubuntu 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:09:21 UTC 2014
ppc64le ppc64le ppc64le GNU/Linux
root@ubuntu:~#
root@ubuntu:~# dpkg --list | grep libc6
ii libc6:ppc64el 2.19-0ubuntu6 ppc64el Embedded GNU C Library: Shared libraries
ii libc6-dbg:ppc64el 2.19-0ubuntu6 ppc64el Embedded GNU C Library: detached
debugging symbols
ii libc6-dev:ppc64el 2.19-0ubuntu6 ppc64el Embedded GNU C Library: Development
Libraries and Header Files
root@ubuntu:~#
The fix is available at the upstream commit:
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=aa5f0ff11ad2cc85277c64cf65c723a9664e1149
** Affects: eglibc (Ubuntu)
Importance: Undecided
Status: New
** Affects: eglibc (Ubuntu Trusty)
Importance: Undecided
Status: New
** Also affects: eglibc (Ubuntu Trusty)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1333506
Title:
frexpl math library function is showing wrong output when value
slightly smaller than a power of two is passed
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