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* [Bug math/9783] New: fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled
@ 2009-01-24 15:38 abramo dot bagnara at gmail dot com
2010-05-04 17:16 ` [Bug math/9783] " mattst88 at gmail dot com
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: abramo dot bagnara at gmail dot com @ 2009-01-24 15:38 UTC (permalink / raw)
To: glibc-bugs
Running the program below, it seems that if feenableexcept(FE_INEXACT) is not
called fetestexcept(FE_INEXACT) doesn't work as expected (and as C99 standard
provides).
Please note that according to documentation GNU extension
feenableexcept/fedisablexcept does not enable/disable inexact detection, but
does enable/disable inexact *trapping* via SIGFPE signal.
Also please ignore the incorrect return from the overly simplified signal
handler (it would generate an infinite loop on some architectures).
The bug was previously believed a gcc one
(http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37581),
but recently we got new info that shows this is not true.
$ cat sf2.c
#define _GNU_SOURCE
#include <fenv.h>
#include <signal.h>
#include <stdio.h>
static void foo (int sig)
{
printf("inexact\n");
}
float __attribute__((noinline)) test (float x) {
printf("%f / %f\n", 2.0f, x);
return 2.0f / x;
}
void t()
{
volatile float x;
feclearexcept (FE_ALL_EXCEPT);
x = test (3.0f);
printf("fetestexcept(FE_INEXACT) = %d\n", fetestexcept(FE_INEXACT));
feclearexcept (FE_ALL_EXCEPT);
x = test (2.0f);
printf("fetestexcept(FE_INEXACT) = %d\n", fetestexcept(FE_INEXACT));
}
int main() {
printf("\nWith FE_INEXACT SIGFPE disabled\n");
t();
printf("\nWith FE_INEXACT SIGFPE enabled\n");
signal (SIGFPE, foo);
feenableexcept (FE_INEXACT);
t();
}
$ gcc -O2 -lm -mieee-with-inexact sf2.c
$ ./a.out
With FE_INEXACT SIGFPE disabled
2.000000 / 3.000000
fetestexcept(FE_INEXACT) = 0
2.000000 / 2.000000
fetestexcept(FE_INEXACT) = 0
With FE_INEXACT SIGFPE enabled
2.000000 / 3.000000
inexact
fetestexcept(FE_INEXACT) = 2097152
2.000000 / 2.000000
fetestexcept(FE_INEXACT) = 0
$
--
Summary: fetestexcept(FE_INEXACT) does not return expected result
when inexact trapping is disabled
Product: glibc
Version: 2.8
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: aj at suse dot de
ReportedBy: abramo dot bagnara at gmail dot com
CC: bagnara at cs dot unipr dot it,glibc-bugs at sources dot
redhat dot com
GCC build triplet: alphaev56-unknown-linux-gnu
GCC host triplet: alphaev56-unknown-linux-gnu
GCC target triplet: alphaev56-unknown-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=9783
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* [Bug math/9783] fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled
2009-01-24 15:38 [Bug math/9783] New: fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled abramo dot bagnara at gmail dot com
@ 2010-05-04 17:16 ` mattst88 at gmail dot com
2010-05-04 17:17 ` mattst88 at gmail dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: mattst88 at gmail dot com @ 2010-05-04 17:16 UTC (permalink / raw)
To: glibc-bugs
------- Additional Comments From mattst88 at gmail dot com 2010-05-04 17:16 -------
Can you still reproduce this? I just ran your test program on my UP1500 and and
could not reproduce:
# gcc -O2 -mcpu=ev67 -o sf2 -lm -mieee-with-inexact sf2.c
UP1500 ~ # ./sf2
With FE_INEXACT SIGFPE disabled
2.000000 / 3.000000
fetestexcept(FE_INEXACT) = 2097152
2.000000 / 2.000000
fetestexcept(FE_INEXACT) = 0
With FE_INEXACT SIGFPE enabled
2.000000 / 3.000000
inexact
fetestexcept(FE_INEXACT) = 2097152
2.000000 / 2.000000
fetestexcept(FE_INEXACT) = 0
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |mattst88 at gmail dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=9783
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug math/9783] fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled
2009-01-24 15:38 [Bug math/9783] New: fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled abramo dot bagnara at gmail dot com
2010-05-04 17:16 ` [Bug math/9783] " mattst88 at gmail dot com
@ 2010-05-04 17:17 ` mattst88 at gmail dot com
2010-05-05 9:35 ` bagnara at cs dot unipr dot it
2010-09-12 23:01 ` mattst88 at gmail dot com
3 siblings, 0 replies; 6+ messages in thread
From: mattst88 at gmail dot com @ 2010-05-04 17:17 UTC (permalink / raw)
To: glibc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |WAITING
http://sourceware.org/bugzilla/show_bug.cgi?id=9783
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug math/9783] fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled
2009-01-24 15:38 [Bug math/9783] New: fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled abramo dot bagnara at gmail dot com
2010-05-04 17:16 ` [Bug math/9783] " mattst88 at gmail dot com
2010-05-04 17:17 ` mattst88 at gmail dot com
@ 2010-05-05 9:35 ` bagnara at cs dot unipr dot it
2010-09-12 23:01 ` mattst88 at gmail dot com
3 siblings, 0 replies; 6+ messages in thread
From: bagnara at cs dot unipr dot it @ 2010-05-05 9:35 UTC (permalink / raw)
To: glibc-bugs
------- Additional Comments From bagnara at cs dot unipr dot it 2010-05-05 09:34 -------
The only Alpha machine we had access to was gcc30's of the GCC Compile Farm
Project. According to http://gcc.gnu.org/wiki/CompileFarm this is now offline,
waiting for relocation.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=9783
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug math/9783] fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled
2009-01-24 15:38 [Bug math/9783] New: fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled abramo dot bagnara at gmail dot com
` (2 preceding siblings ...)
2010-05-05 9:35 ` bagnara at cs dot unipr dot it
@ 2010-09-12 23:01 ` mattst88 at gmail dot com
3 siblings, 0 replies; 6+ messages in thread
From: mattst88 at gmail dot com @ 2010-09-12 23:01 UTC (permalink / raw)
To: glibc-bugs
------- Additional Comments From mattst88 at gmail dot com 2010-09-12 23:01 -------
(In reply to comment #2)
> The only Alpha machine we had access to was gcc30's of the GCC Compile Farm
> Project. According to http://gcc.gnu.org/wiki/CompileFarm this is now offline,
> waiting for relocation.
I tested on another Alpha, with glibc-2.11, and got the same results as I did
before.
I'm going to close this bug as resolved. Please reopen if someone finds otherwise.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution| |FIXED
http://sourceware.org/bugzilla/show_bug.cgi?id=9783
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[parent not found: <bug-9783-131@http.sourceware.org/bugzilla/>]
end of thread, other threads:[~2014-07-01 21:02 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-01-24 15:38 [Bug math/9783] New: fetestexcept(FE_INEXACT) does not return expected result when inexact trapping is disabled abramo dot bagnara at gmail dot com
2010-05-04 17:16 ` [Bug math/9783] " mattst88 at gmail dot com
2010-05-04 17:17 ` mattst88 at gmail dot com
2010-05-05 9:35 ` bagnara at cs dot unipr dot it
2010-09-12 23:01 ` mattst88 at gmail dot com
[not found] <bug-9783-131@http.sourceware.org/bugzilla/>
2014-07-01 21:02 ` fweimer at redhat dot com
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