Issue #15477: Add workaround for log1p(-0.0) on platforms where it's broken.
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 @@
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 @@
return log(1.+x);
}
}
+
+#endif /* ifdef HAVE_LOG1P */