From 59a63cca1133a8e1e3219970ee95979ac1f810df Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Fri, 2 Oct 2015 17:11:13 +0000 Subject: 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. --- math/libm-test.inc | 4 ++++ math/s_nexttowardf.c | 4 ++-- 2 files changed, 6 insertions(+), 2 deletions(-) (limited to 'math') diff --git a/math/libm-test.inc b/math/libm-test.inc index f627296d66..ac1fe85fc1 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 06e1bb10cb..06350d47bf 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 */ -- cgit 1.4.1