1 files changed, 35 insertions, 0 deletions
diff --git a/Include/pyport.h b/Include/pyport.h
index a831b26..b311bd8 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -287,6 +287,41 @@ extern "C" {
 			errno = ERANGE; \
 	} while(0)
 
+/* Py_ADJUST_ERANGE1(x)
+ * Py_ADJUST_ERANGE2(x, y)
+ * Set errno to 0 before calling a libm function, and invoke one of these
+ * macros after, passing the function result(s) (Py_ADJUST_ERANGE2 is useful
+ * for functions returning complex results).  This makes two kinds of
+ * adjustments to errno:  (A) If it looks like the platform libm set
+ * errno=ERANGE due to underflow, clear errno. (B) If it looks like the
+ * platform libm overflowed but didn't set errno, force errno to ERANGE.  In
+ * effect, we're trying to force a useful implementation of C89 errno
+ * behavior.
+ * Caution:
+ *    This isn't reliable.  See Py_OVERFLOWED comments.
+ *    X and Y may be evaluated more than once.
+ */
+#define Py_ADJUST_ERANGE1(X)						\
+	do {								\
+		if (errno == 0) {					\
+			if ((X) == Py_HUGE_VAL || (X) == -Py_HUGE_VAL)	\
+				errno = ERANGE;				\
+		}							\
+		else if (errno == ERANGE && (X) == 0.0)			\
+			errno = 0;					\
+	} while(0)
+
+#define Py_ADJUST_ERANGE2(X, Y)						\
+	do {								\
+		if ((X) == Py_HUGE_VAL || (X) == -Py_HUGE_VAL ||	\
+		    (Y) == Py_HUGE_VAL || (Y) == -Py_HUGE_VAL) {	\
+				if (errno == 0)				\
+					errno = ERANGE;			\
+		}							\
+		else if (errno == ERANGE)				\
+			errno = 0;					\
+	} while(0)
+
 /**************************************************************************
 Prototypes that are missing from the standard include files on some systems
 (and possibly only some versions of such systems.)