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| author | Joseph Myers <joseph@codesourcery.com> | 2015-10-02 17:11:13 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-10-02 17:11:13 +0000 |
| commit | 59a63cca1133a8e1e3219970ee95979ac1f810df (patch) | |
| tree | a4fc7c389f60647377479748d75bcc94f3c36547 /math | |
| parent | ef6b619f73e49b6d87c7530e6e9f8a59723b492d (diff) | |
| download | glibc-59a63cca1133a8e1e3219970ee95979ac1f810df.zip glibc-59a63cca1133a8e1e3219970ee95979ac1f810df.tar.gz glibc-59a63cca1133a8e1e3219970ee95979ac1f810df.tar.bz2 | |
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.
Diffstat (limited to 'math')
| -rw-r--r-- | math/libm-test.inc | 4 | ||||
| -rw-r--r-- | math/s_nexttowardf.c | 4 |
2 files changed, 6 insertions, 2 deletions
diff --git a/math/libm-test.inc b/math/libm-test.inc index f627296..ac1fe85 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -8536,6 +8536,10 @@ static const struct test_ff_f_data_nexttoward nexttoward_test_data[] = TEST_ff_f (nexttoward, 1.1L, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED), TEST_ff_f (nexttoward, qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED), + /* Bug 6799: errno setting may be missing. */ + TEST_ff_f (nexttoward, max_value, plus_infty, plus_infty, INEXACT_EXCEPTION|OVERFLOW_EXCEPTION), + TEST_ff_f (nexttoward, -max_value, minus_infty, minus_infty, INEXACT_EXCEPTION|OVERFLOW_EXCEPTION), + #ifdef TEST_FLOAT TEST_ff_f (nexttoward, 1.0, 1.1L, 0x1.000002p0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED), TEST_ff_f (nexttoward, 1.0, LDBL_MAX, 0x1.000002p0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED), diff --git a/math/s_nexttowardf.c b/math/s_nexttowardf.c index 06e1bb1..06350d4 100644 --- a/math/s_nexttowardf.c +++ b/math/s_nexttowardf.c @@ -59,8 +59,8 @@ float __nexttowardf(float x, long double y) } hy = hx&0x7f800000; if(hy>=0x7f800000) { - x = math_narrow_eval (x+x); /* overflow */ - return x; + float u = x+x; /* overflow */ + math_force_eval (u); } if(hy<0x00800000) { float u = x*x; /* underflow */ |