[Bug math/16977] New: log10 (1) incorrect in round-downward mode

[Bug math/16977] New: log10 (1) incorrect in round-downward mode

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16977

            Bug ID: 16977
           Summary: log10 (1) incorrect in round-downward mode
           Product: glibc
           Version: 2.19
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: jsm28 at gcc dot gnu.org

As per ISO C Annex F, log10 (1) should be +0 in all rounding modes.  However,
it returns -1 in round-downward mode for x86_64 for long double, for x86 for
all types, and maybe in other cases.

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[Bug math/16977] log10 (1) incorrect in round-downward mode

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16977

--- Comment #1 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
(Returns -0, not -1, that is.)

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[Bug math/16977] log10 (1) incorrect in round-downward mode

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16977

--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
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The branch, master has been updated
       via  b72592e75fdecb34e2ac5f931730409a1fb68e8a (commit)
      from  2302d679ce8b36854022207b58e554b3e89dd8c7 (commit)

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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b72592e75fdecb34e2ac5f931730409a1fb68e8a

commit b72592e75fdecb34e2ac5f931730409a1fb68e8a
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Fri May 23 12:07:50 2014 +0000

    Fix log10 (1) in round-downward mode (bug 16977).

    As with various other issues of this kind, bug 16977 is log10 (1)
    wrongly returning -0 rather than +0 in round-downward mode because of
    an implementation effectively in terms of log1p (x - 1).  This patch
    fixes the issue in the same way used for log.

    Tested x86_64 and x86 and ulps updated accordingly.  Also tested for
    mips64 to confirm a fix was needed for ldbl-128 and to validate that
    fix (also applied to ldbl-128ibm since that version of logl is
    essentially the same as the ldbl-128 one).

        [BZ #16977]
        * sysdeps/i386/fpu/e_log10.S (__ieee754_log10): Take absolute
        value when x - 1 is zero.
        * sysdeps/i386/fpu/e_log10f.S (__ieee754_log10f): Likewise.
        * sysdeps/i386/fpu/e_log10l.S (__ieee754_log10l): Likewise.
        * sysdeps/ieee754/ldbl-128/e_log10l.c (__ieee754_log10l): Return
        0.0L for an argument of 1.0L.
        * sysdeps/ieee754/ldbl-128ibm/e_log10l.c (__ieee754_log10l):
        Likewise.
        * sysdeps/x86_64/fpu/e_log10l.S (__ieee754_log10l): Take absolute
        value when x - 1 is zero.
        * math/libm-test.inc (log10_test): Use ALL_RM_TEST.
        * sysdeps/i386/fpu/libm-test-ulps: Update.
        * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

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

Summary of changes:
 ChangeLog                              |   17 +++++++++++++++++
 NEWS                                   |    2 +-
 math/libm-test.inc                     |    4 +---
 sysdeps/i386/fpu/e_log10.S             |    8 +++++++-
 sysdeps/i386/fpu/e_log10f.S            |    8 +++++++-
 sysdeps/i386/fpu/e_log10l.S            |    8 +++++++-
 sysdeps/i386/fpu/libm-test-ulps        |   24 ++++++++++++++++++++++++
 sysdeps/ieee754/ldbl-128/e_log10l.c    |    3 +++
 sysdeps/ieee754/ldbl-128ibm/e_log10l.c |    3 +++
 sysdeps/x86_64/fpu/e_log10l.S          |    8 +++++++-
 sysdeps/x86_64/fpu/libm-test-ulps      |   24 ++++++++++++++++++++++++
 11 files changed, 101 insertions(+), 8 deletions(-)

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[Bug math/16977] log10 (1) incorrect in round-downward mode

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16977

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

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

--- Comment #3 from Joseph Myers <jsm28 at gcc dot gnu.org> ---
Fixed for 2.20.

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[Bug math/16977] log10 (1) incorrect in round-downward mode

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16977

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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