[Bug math/16564] New: Bad overflowing log1p results

[Bug math/16564] New: Bad overflowing log1p results

[zimmerma+gcc at loria dot fr]

https://sourceware.org/bugzilla/show_bug.cgi?id=16564

            Bug ID: 16564
           Summary: Bad overflowing log1p results
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: zimmerma+gcc at loria dot fr

on x86_64 with extended precision:

Testing function log1p for exponent 0 [seed=16203].
 rounding mode MPFR_RNDU:
      wrong overflow flag: mpfr gives 0, library 8
      x=f.fffffffffffffff0@4095
      library gives @Inf@
      mpfr    gives 2.c5c85fdf473de6b0@3

Since log(1+x) is always in the representable range, we should not get +Inf.
(Presumably 1+x is computed with rounding up and yields +Inf, then log(+Inf)
gives +Inf.)

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[Bug math/16564] Bad overflowing log1p results

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16564

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1a84c3d6d4bc43c92b6531b09d732e2e9c750dea

commit 1a84c3d6d4bc43c92b6531b09d732e2e9c750dea
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed May 14 12:38:56 2014 +0000

    Fix log1pl (LDBL_MAX) in FE_UPWARD mode (bug 16564).

    Bug 16564 is spurious overflow of log1pl (LDBL_MAX) in FE_UPWARD mode,
    resulting from log1pl adding 1 to its argument (for arguments not
    close to 0), which overflows in that mode.  This patch fixes this by
    avoiding adding 1 to large arguments (precisely what counts as large
    depends on the floating-point format).

    Tested x86_64 and x86, and spot-checked log1pl tests on mips64 and
    powerpc64.

        [BZ #16564]
        * sysdeps/i386/fpu/s_log1pl.S (__log1pl): Do not add 1 to positive
        arguments with exponent 65 or above.
        * sysdeps/ieee754/ldbl-128/s_log1pl.c (__log1pl): Do not add 1 to
        arguments 0x1p113L or above.
        * sysdeps/ieee754/ldbl-128ibm/s_log1pl.c (__log1pl): Do not add 1
        to arguments 0x1p107L or above.
        * sysdeps/x86_64/fpu/s_log1pl.S (__log1pl): Do not add 1 to
        positive arguments with exponent 65 or above.
        * math/auto-libm-test-in: Add more tests of log1p.
        * math/auto-libm-test-out: Regenerated.

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

Summary of changes:
 ChangeLog                              |   12 ++
 NEWS                                   |   14 +-
 math/auto-libm-test-in                 |    8 +
 math/auto-libm-test-out                |  264 ++++++++++++++++++++++++++++++++
 sysdeps/i386/fpu/s_log1pl.S            |    7 +-
 sysdeps/ieee754/ldbl-128/s_log1pl.c    |    5 +-
 sysdeps/ieee754/ldbl-128ibm/s_log1pl.c |    5 +-
 sysdeps/x86_64/fpu/s_log1pl.S          |    7 +-
 8 files changed, 311 insertions(+), 11 deletions(-)

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[Bug math/16564] Bad overflowing log1p results

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16564

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 2.20.

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[Bug math/16564] Bad overflowing log1p results

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16564

Florian Weimer <fweimer at redhat dot com> changed:

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

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