On 18/01/11 17:36, Blue Swirl wrote:
On Tue, Jan 18, 2011 at 3:27 PM, Mateusz Loskot<mate...@loskot.net> wrote:
Hi,
Recently, I have reported mysterious issues on NetBSD 5.1
emulated on SPARC. The whole first thread is here:
http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg01509.html
I decided to investigate the problem deeper and with great help
from NetBSD folks, I managed to find reproducible test case.
Initially, it was AWK command:
# echo NaN | awk '{print "test"}'
awk: floating point exception 8
source line number 1
and next it boiled down to simple C program (see below).
Details of the investigation are archived in the NetBSD Problem
Report #44389 here:
http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=44389
Here is final version of the test program which reproduces the problem:
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<errno.h>
int is_number(const char *s)
{
double r;
char *ep;
errno = 0;
r = strtod(s,&ep);
if (r == HUGE_VAL)
printf("X:%g\n", r);
if (ep == s || r == HUGE_VAL || errno == ERANGE)
return 0;
while (*ep == ' ' || *ep == '\t' || *ep == '\n')
ep++;
if (*ep == '\0')
return 1;
else
return 0;
}
int main(int argc, char **argv)
{
double v;
if (is_number("NaN")) {
printf("is a number\n");
v = atof("NaN");
} else {
printf("not a number\n");
v = 0.0;
}
printf("%.4f\n", v);
return 0;
}
On NetBSD/SPARC, the program receives SIGFPE:
$ gcc ./nan_test_2.c
$ ./a.out
[1] Floating point exception (core dumped) ./a.out
Specifically, it's caused by r == HUGE_VAL condition in
if (ep == s || r == HUGE_VAL || errno == ERANGE)
where r is NaN.
All the signs indicate there is a bug in QEMU.
I'll install 5.1, but on 4.0 which I had installed, the program works fine:
$ ./sigfpe
is a number
nan
I just tested on NetBSD 5.0/SPARC under QEMU 0.13 (same version I use
with NetBSD 5.1/SPARC) and it works well indeed:
mloskot@qemu-netbsd-50-sparc:~/tmp# ./a.out
is a number
nan
mloskot@qemu-netbsd-50-sparc:~/tmp#
Hmm, this is becoming interesting.
I run QEMU 0.13 on Windows Vista (64-bit).
Perhaps host system and QEMU binaries are relevant here.
I will try on Linux host system later tonight.
BTW, here are my images:
http://mateusz.loskot.net/tmp/qemu/
Best regards,
--
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org