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.
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 77b56a0..b3b80f4 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -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 */