+#elif defined(_MSC_VER)
+#include <float.h>
+#define isinf(X) (!_finite(X))
+#elif defined(_AIX) && defined(__GNUC__)
+// GCC's fixincludes seems to be removing the isinf() declaration from the
+// system header /usr/include/math.h
+# include <math.h>
+static int isinf(double x) { return !finite(x) && x==x; }
+#elif defined(__hpux)
+// HP-UX is "special"
+#include <math.h>
+static int isinf(double x) { return ((x) == INFINITY) || ((x) == -INFINITY); }