[Bug math/18242] New: powf, powl, do not conform to POSIX for (0, -INFINITY) input

[Bug math/18242] New: powf, powl, do not conform to POSIX for (0, -INFINITY) input

[nszabolcs at gmail dot com]

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https://sourceware.org/bugzilla/show_bug.cgi?id=18242

            Bug ID: 18242
           Summary: powf, powl, do not conform to POSIX for (0, -INFINITY)
                    input
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: nszabolcs at gmail dot com

posix seems to require pow(0, -INFINITY) to raise divbyzero flag.

ISO C Annex F:
pow((+-)0, -(inf)) returns +(inf) and may raise the ''divide-by-zero''
floating-point exception.
http://port70.net/~nsz/c/c11/n1570.html#F.10.4.4

but

POSIX-2008 (2013):
On systems that support the IEC 60559 Floating-Point option, if x is ±0,
a pole error shall occur and pow(), powf(), and powl() shall return
±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL, respectively if y is an odd
integer, or HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively if y is not
an odd integer.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/pow.html


#define _POSIX_C_SOURCE 200809L
#include <fenv.h>
#include <math.h>
#include <stdio.h>


int main()
{
#pragma STDC FENV_ACCESS ON

powf(0, -INFINITY);
if (!fetestexcept(FE_DIVBYZERO))
        printf("powf did not raise div by zero flag.\n");

feclearexcept(FE_ALL_EXCEPT);
// this one works correctly
pow(0, -INFINITY);
if (!fetestexcept(FE_DIVBYZERO))
        printf("pow did not raise div by zero flag.\n");

feclearexcept(FE_ALL_EXCEPT);
powl(0, -INFINITY);
if (!fetestexcept(FE_DIVBYZERO))
        printf("powl did not raise div by zero flag.\n");
}

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From: "nszabolcs at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nptl/18243] New: sem_wait, sem_timedwait are cancellation points shm_open is not
Date: Fri, 10 Apr 2015 12:11:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id\x18243

            Bug ID: 18243
           Summary: sem_wait, sem_timedwait are cancellation points
                    shm_open is not
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: nszabolcs at gmail dot com
                CC: drepper.fsp at gmail dot com

Created attachment 8237
  --> https://sourceware.org/bugzilla/attachment.cgi?id‚37&actioníit
pthread cancellation point test

uncontended sem_wait, sem_timedwait fail to act on cancellation.

shm_open can be cancelled, but it shouldn't.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_09_05

the attached code prints:

res == PTHREAD_CANCELED failed (non-blocking sem_wait, canceled thread exit
status)
res == PTHREAD_CANCELED failed (non-blocking sem_timedwait, canceled thread
exit status)
res != PTHREAD_CANCELED failed (shm_open, canceled thread exit status)

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[Bug math/18242] powf, powl, do not conform to POSIX for (0, -INFINITY) input

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18242

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
The C99 requirement to raise divide-by-zero in this case was a defect, as it
was contrary to IEEE 754 semantics for that exception.  See N1515.  Thus, it's
a defect in POSIX that it hasn't adopted the C11 correction, and the ideal
result would be *never* raising that exception in this case.

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