[Bug math/19088] lround, llround missing exceptions close to overflow threshold

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https://sourceware.org/bugzilla/show_bug.cgi?id=19088

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=8afdb7ac1ecadf82abdb16a5fcfadf9537ca3d84

commit 8afdb7ac1ecadf82abdb16a5fcfadf9537ca3d84
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Oct 7 23:45:29 2015 +0000

    Fix lround, llround missing exceptions close to overflow threshold (bug
19088).

    The dbl-64, ldbl-96 and ldbl-128 implementations of lround and llround
    fail to produce "invalid" exceptions in cases where the rounded result
    overflows the target type, but truncating the floating-point argument
    to the next integer towards zero does not overflow it (so in
    particular casts do not produce such exceptions).  (This issue cannot
    arise for float, or for double with 64-bit target type, or for ldbl-96
    with 64-bit target type and negative arguments, because of
    insufficient precision in the floating-point type for arguments with
    the relevant property to exist.)

    This patch fixes these problems by inserting checks for the special
    cases that can occur in each implementation, and explicitly raising
    FE_INVALID (and avoiding the cast if it might raise spurious
    FE_INEXACT).

    Tested for x86_64, x86 and mips64.

        [BZ #19088]
        * sysdeps/ieee754/dbl-64/s_lround.c: Include <fenv.h> and
        <limits.h>.
        (__lround) [FE_INVALID]: Force FE_INVALID exception when result
        overflows but exception would not result from cast.
        * sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c: Include <fenv.h>
        and <limits.h>.
        (__lround) [FE_INVALID]: Force FE_INVALID exception when result
        overflows but exception would not result from cast.
        * sysdeps/ieee754/ldbl-128/s_llroundl.c: Include <fenv.h> and
        <limits.h>.
        (__llroundl) [FE_INVALID]: Force FE_INVALID exception when result
        overflows but exception would not result from cast.
        * sysdeps/ieee754/ldbl-128/s_lroundl.c: Include <fenv.h> and
        <limits.h>.
        (__lroundl) [FE_INVALID]: Force FE_INVALID exception when result
        overflows but exception would not result from cast.
        * sysdeps/ieee754/ldbl-96/s_llroundl.c: Include <fenv.h> and
        <limits.h>.
        (__llroundl) [FE_INVALID]: Force FE_INVALID exception when result
        overflows but exception would not result from cast.
        * sysdeps/ieee754/ldbl-96/s_lroundl.c: Include <fenv.h> and
        <limits.h>.
        (__lroundl) [FE_INVALID]: Force FE_INVALID exception when result
        overflows but exception would not result from cast.
        * math/libm-test.inc (lround_test_data): Add more tests.
        (llround_test_data): Likewise.

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

Summary of changes:
 ChangeLog                                     |   30 ++++
 NEWS                                          |    2 +-
 math/libm-test.inc                            |  185 +++++++++++++++++++++++++
 sysdeps/ieee754/dbl-64/s_lround.c             |   28 ++++-
 sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c |   24 +++-
 sysdeps/ieee754/ldbl-128/s_llroundl.c         |   25 +++-
 sysdeps/ieee754/ldbl-128/s_lroundl.c          |   32 ++++-
 sysdeps/ieee754/ldbl-96/s_llroundl.c          |   11 ++-
 sysdeps/ieee754/ldbl-96/s_lroundl.c           |   35 +++++-
 9 files changed, 358 insertions(+), 14 deletions(-)

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