[Bug math/18244] New: remquol(x, INFINITY, &quo) is wrong on x86_64

[Bug math/18244] New: remquol(x, INFINITY, &quo) is wrong on x86_64

[nszabolcs at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18244

            Bug ID: 18244
           Summary: remquol(x, INFINITY, &quo) is wrong on x86_64
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: nszabolcs at gmail dot com

remquol(x, INFINITY, &quo) should return x (that's the remainder)

the following code on linux x86_64 prints:
remquol(42,inf) = -nan  quo = 0  invalid=1
remquol(42,-inf) = -nan  quo = 0  invalid=1


#include <fenv.h>
#include <math.h>
#include <stdio.h>

int main()
{
#pragma STDC FENV_ACCESS ON
int quo;
long double r;

feclearexcept(FE_ALL_EXCEPT);
r = remquol(42, INFINITY, &quo);
if (r != 42)
        printf("remquol(42,inf) = %La  quo = %d  invalid=%d\n", r, quo,
fetestexcept(FE_INVALID));

feclearexcept(FE_ALL_EXCEPT);
r = remquol(42, -INFINITY, &quo);
if (r != 42)
        printf("remquol(42,-inf) = %La  quo = %d  invalid=%d\n", r, quo,
fetestexcept(FE_INVALID));
}

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[Bug math/18244] remquol(x, INFINITY, &quo) is wrong on x86_64

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18244

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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=3ce2232efb008e129908b9f35c4266991d9361de

commit 3ce2232efb008e129908b9f35c4266991d9361de
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Tue May 19 23:44:28 2015 +0000

    Fix ldbl-96 remquol (finite, Inf) (bug 18244).

    ldbl-96 remquol wrongly handles the case where the first argument is
    finite and the second infinite, because the check for the second
    argument being a NaN fails to disregard the explicit high mantissa bit
    and so wrongly interprets an infinity as being a NaN.  This patch
    fixes this by masking off that bit, and improves test coverage for
    both remainder and remquo (various cases were missing tests, or, as in
    the case of the bug, were tested only for one of the two functions).

    Tested for x86_64 and x86.

        [BZ #18244]
        * sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Ignore explicit
        high mantissa bit when testing whether P is a NaN.
        * math/libm-test.inc (remainder_test_data): Add more tests.
        (remquo_test_data): Likewise.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                           |    6 +++++
 NEWS                                |    4 +-
 math/libm-test.inc                  |   37 +++++++++++++++++++++++++++++++++++
 sysdeps/ieee754/ldbl-96/s_remquol.c |    2 +-
 4 files changed, 46 insertions(+), 3 deletions(-)

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[Bug math/18244] remquol(x, INFINITY, &quo) is wrong on x86_64

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18244

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

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

--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.22.

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