diff options
| -rw-r--r-- | Lib/test/test_cmath.py | 4 | ||||
| -rw-r--r-- | Misc/NEWS | 3 | ||||
| -rw-r--r-- | Modules/_math.c | 23 | ||||
| -rw-r--r-- | Modules/_math.h | 8 |
4 files changed, 28 insertions, 10 deletions
diff --git a/Lib/test/test_cmath.py b/Lib/test/test_cmath.py index 4e93be4..692ea36 100644 --- a/Lib/test/test_cmath.py +++ b/Lib/test/test_cmath.py @@ -519,15 +519,11 @@ class CMathTests(unittest.TestCase): # of zero, then atan and atanh will also have difficulties with # the sign of complex zeros. @requires_IEEE_754 - @unittest.skipIf(sysconfig.get_config_var('LOG1P_DROPS_ZERO_SIGN'), - "system log1p() function doesn't preserve the sign") def testAtanSign(self): for z in complex_zeros: self.assertComplexIdentical(cmath.atan(z), z) @requires_IEEE_754 - @unittest.skipIf(sysconfig.get_config_var('LOG1P_DROPS_ZERO_SIGN'), - "system log1p() function doesn't preserve the sign") def testAtanhSign(self): for z in complex_zeros: self.assertComplexIdentical(cmath.atanh(z), z) @@ -16,6 +16,9 @@ Core and Builtins Library ------- +- Issue #15477: In cmath and math modules, add workaround for platforms whose + system-supplied log1p function doesn't respect signs of zeros. + - Issue #15715: importlib.__import__() will silence an ImportError when the use of fromlist leads to a failed import. diff --git a/Modules/_math.c b/Modules/_math.c index 2fef481..fe75a36 100644 --- a/Modules/_math.c +++ b/Modules/_math.c @@ -189,6 +189,27 @@ _Py_expm1(double x) significant loss of precision that arises from direct evaluation when x is small. */ +#ifdef HAVE_LOG1P + +double +_Py_log1p(double x) +{ + /* Some platforms supply a log1p function but don't respect the sign of + zero: log1p(-0.0) gives 0.0 instead of the correct result of -0.0. + + To save fiddling with configure tests and platform checks, we handle the + special case of zero input directly on all platforms. + */ + if (x == 0.0) { + return x; + } + else { + return log1p(x); + } +} + +#else + double _Py_log1p(double x) { @@ -230,3 +251,5 @@ _Py_log1p(double x) return log(1.+x); } } + +#endif /* ifdef HAVE_LOG1P */ diff --git a/Modules/_math.h b/Modules/_math.h index c0ceece..cf079ad 100644 --- a/Modules/_math.h +++ b/Modules/_math.h @@ -36,10 +36,6 @@ double _Py_log1p(double x); #define m_expm1 _Py_expm1 #endif -#ifdef HAVE_LOG1P -#define m_log1p log1p -#else -/* if the system doesn't have log1p, use the substitute - function defined in Modules/_math.c. */ +/* Use the substitute from _math.c on all platforms: + it includes workarounds for buggy handling of zeros. */ #define m_log1p _Py_log1p -#endif |