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Make cacosh (0 + iNaN) return NaN + i pi/2 (bug 22561, DR#471) [committed]
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Wed, 6 Dec 2017 21:36:35 +0000
- Subject: Make cacosh (0 + iNaN) return NaN + i pi/2 (bug 22561, DR#471) [committed]
- Authentication-results: sourceware.org; auth=none
As per C11 DR#471 (adjusted resolution accepted for C17), cacosh (0 +
iNaN) should return NaN +/- i pi/2, not NaN + iNaN.
This patch fixes the code accordingly. The test has hardcoded the
result with positive sign of the imaginary part (with an associated
comment), since the unspecified sign for a result other than 0 or
infinity isn't currently supported by the test infrastructure.
Tested for x86_64. Committed.
2017-12-06 Joseph Myers <joseph@codesourcery.com>
[BZ #22561]
* math/s_cacosh_template.c (M_DECL_FUNC (__cacosh)): Use pi/2 for
real part of result for argument 0 + i * NaN.
* math/libm-test-cacosh.inc (cacosh_test_data): Update expected
results for tests of 0 + i * NaN.
diff --git a/math/libm-test-cacosh.inc b/math/libm-test-cacosh.inc
index 518cb29..db700b9 100644
--- a/math/libm-test-cacosh.inc
+++ b/math/libm-test-cacosh.inc
@@ -46,8 +46,13 @@ static const struct test_c_c_data cacosh_test_data[] =
TEST_c_c (cacosh, plus_infty, qnan_value, plus_infty, qnan_value),
TEST_c_c (cacosh, minus_infty, qnan_value, plus_infty, qnan_value),
- TEST_c_c (cacosh, 0, qnan_value, qnan_value, qnan_value),
- TEST_c_c (cacosh, minus_zero, qnan_value, qnan_value, qnan_value),
+ /* The sign of the imaginary part of the result is unspecified
+ (see
+ <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2173.htm>),
+ but the libm-test infrastructure does not support describing
+ that. */
+ TEST_c_c (cacosh, 0, qnan_value, qnan_value, lit_pi_2_d),
+ TEST_c_c (cacosh, minus_zero, qnan_value, qnan_value, lit_pi_2_d),
TEST_c_c (cacosh, qnan_value, plus_infty, plus_infty, qnan_value),
TEST_c_c (cacosh, qnan_value, minus_infty, plus_infty, qnan_value),
diff --git a/math/s_cacosh_template.c b/math/s_cacosh_template.c
index 14f0b2a..0014fd4 100644
--- a/math/s_cacosh_template.c
+++ b/math/s_cacosh_template.c
@@ -57,7 +57,10 @@ M_DECL_FUNC (__cacosh) (CFLOAT x)
else
{
__real__ res = M_NAN;
- __imag__ res = M_NAN;
+ if (rcls == FP_ZERO)
+ __imag__ res = M_MLIT (M_PI_2);
+ else
+ __imag__ res = M_NAN;
}
}
else if (rcls == FP_ZERO && icls == FP_ZERO)
--
Joseph S. Myers
joseph@codesourcery.com