[Bug math/19059] New: nexttoward overflow incorrect in non-default rounding modes

[Bug math/19059] New: nexttoward overflow incorrect in non-default rounding modes

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19059

            Bug ID: 19059
           Summary: nexttoward overflow incorrect in non-default rounding
                    modes
           Product: glibc
           Version: 2.22
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: jsm28 at gcc dot gnu.org
  Target Milestone: ---

ISO C requires overflowing results from nexttoward to be the appropriate
infinity independent of the rounding mode, but some implementations use a
rounding-mode-dependent result (this is the same issue as was fixed for
nextafter in bug 16677).  E.g., for float on x86_64:

Failure: Test: nexttoward_downward (max_value, inf)
Result:
 is:          3.40282346e+38   0x1.fffffep+127
 should be:   inf   inf
Failure: Test: nexttoward_towardzero (max_value, inf)
Result:
 is:          3.40282346e+38   0x1.fffffep+127
 should be:   inf   inf
Failure: Test: nexttoward_towardzero (-max_value, -inf)
Result:
 is:         -3.40282346e+38  -0x1.fffffep+127
 should be:  -inf  -inf
Failure: Test: nexttoward_upward (-max_value, -inf)
Result:
 is:         -3.40282346e+38  -0x1.fffffep+127
 should be:  -inf  -inf

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[Bug math/19059] nexttoward overflow incorrect in non-default rounding modes

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19059

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |2.23

--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.23.

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[Bug math/19059] nexttoward overflow incorrect in non-default rounding modes

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19059

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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The branch, master has been updated
       via  59a63cca1133a8e1e3219970ee95979ac1f810df (commit)
      from  ef6b619f73e49b6d87c7530e6e9f8a59723b492d (commit)

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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=59a63cca1133a8e1e3219970ee95979ac1f810df

commit 59a63cca1133a8e1e3219970ee95979ac1f810df
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Fri Oct 2 17:11:13 2015 +0000

    Fix nexttoward overflow in non-default rounding modes (bug 19059).

    ISO C requires overflowing results from nexttoward to be the
    appropriate infinity independent of the rounding mode, but some
    implementations use a rounding-mode-dependent result (this is the same
    issue as was fixed for nextafter in bug 16677).  This patch fixes the
    problem by making the nexttoward implementations discard the result
    from the floating-point computation that forced an overflow exception
    and then return the infinity previously computed with integer
    arithmetic.

    Tested for x86_64, x86, mips64 and powerpc.

        [BZ #19059]
        * math/s_nexttowardf.c (__nexttowardf): Do not return value from
        overflowing computation.
        * sysdeps/i386/fpu/s_nexttoward.c (__nexttoward): Likewise.
        * sysdeps/i386/fpu/s_nexttowardf.c (__nexttowardf): Likewise.
        * sysdeps/ieee754/ldbl-128/s_nexttoward.c (__nexttoward):
        Likewise.
        * sysdeps/ieee754/ldbl-128/s_nexttowardf.c (__nexttowardf):
        Likewise.
        * sysdeps/ieee754/ldbl-128ibm/s_nexttoward.c (__nexttoward):
        Likewise.
        * sysdeps/ieee754/ldbl-128ibm/s_nexttowardf.c (__nexttowardf):
        Likewise.
        * sysdeps/ieee754/ldbl-96/s_nexttoward.c (__nexttoward): Likewise.
        * sysdeps/ieee754/ldbl-96/s_nexttowardf.c (__nexttowardf):
        Likewise.
        * sysdeps/ieee754/ldbl-opt/s_nexttowardfd.c (__nldbl_nexttowardf):
        Likewise.
        * math/libm-test.inc (nexttoward_test_data): Add more tests.

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

Summary of changes:
 ChangeLog                                   |   20 ++++++++++++++++++++
 NEWS                                        |    2 +-
 math/libm-test.inc                          |    4 ++++
 math/s_nexttowardf.c                        |    4 ++--
 sysdeps/i386/fpu/s_nexttoward.c             |    4 ++--
 sysdeps/i386/fpu/s_nexttowardf.c            |    4 ++--
 sysdeps/ieee754/ldbl-128/s_nexttoward.c     |    4 ++--
 sysdeps/ieee754/ldbl-128/s_nexttowardf.c    |    5 ++++-
 sysdeps/ieee754/ldbl-128ibm/s_nexttoward.c  |    4 ++--
 sysdeps/ieee754/ldbl-128ibm/s_nexttowardf.c |    4 ++--
 sysdeps/ieee754/ldbl-96/s_nexttoward.c      |    4 ++--
 sysdeps/ieee754/ldbl-96/s_nexttowardf.c     |    4 ++--
 sysdeps/ieee754/ldbl-opt/s_nexttowardfd.c   |    4 ++--
 13 files changed, 47 insertions(+), 20 deletions(-)

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