Mercurial > cpython-lru_cache-weakref
diff Modules/mathmodule.c @ 62317:d064e8934f4d
Merged revisions 81967 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r81967 | mark.dickinson | 2010-06-13 11:50:29 +0100 (Sun, 13 Jun 2010) | 4 lines
Issue #8986: erfc was raising OverflowError on Linux for arguments in
the (approximate) range (-27.3, 30.0), as a result of an escaped errno
value.
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| author | Mark Dickinson <dickinsm@gmail.com> |
|---|---|
| date | Sun, 13 Jun 2010 10:52:38 +0000 |
| parents | 1e149b50aca6 |
| children | 1c5c146de642 |
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--- a/Modules/mathmodule.c Sun Jun 13 09:17:13 2010 +0000 +++ b/Modules/mathmodule.c Sun Jun 13 10:52:38 2010 +0000 @@ -428,8 +428,8 @@ static double m_erf_series(double x) { - double x2, acc, fk; - int i; + double x2, acc, fk, result; + int i, saved_errno; x2 = x * x; acc = 0.0; @@ -438,7 +438,12 @@ acc = 2.0 + x2 * acc / fk; fk -= 1.0; } - return acc * x * exp(-x2) / sqrtpi; + /* Make sure the exp call doesn't affect errno; + see m_erfc_contfrac for more. */ + saved_errno = errno; + result = acc * x * exp(-x2) / sqrtpi; + errno = saved_errno; + return result; } /* @@ -453,8 +458,8 @@ static double m_erfc_contfrac(double x) { - double x2, a, da, p, p_last, q, q_last, b; - int i; + double x2, a, da, p, p_last, q, q_last, b, result; + int i, saved_errno; if (x >= ERFC_CONTFRAC_CUTOFF) return 0.0; @@ -472,7 +477,12 @@ temp = p; p = b*p - a*p_last; p_last = temp; temp = q; q = b*q - a*q_last; q_last = temp; } - return p / q * x * exp(-x2) / sqrtpi; + /* Issue #8986: On some platforms, exp sets errno on underflow to zero; + save the current errno value so that we can restore it later. */ + saved_errno = errno; + result = p / q * x * exp(-x2) / sqrtpi; + errno = saved_errno; + return result; } /* Error function erf(x), for general x */