negative = 1;
exponent = -exponent;
}
-#ifdef __VAX /* avoid %SYSTEM-F-FLTOVF_F sans VAXC$ESTABLISH */
+
+ /* Avoid %SYSTEM-F-FLTOVF_F sans VAXC$ESTABLISH.
+ * In VAX VMS we by default use the D_FLOAT double format,
+ * and that format does not have *easy* capabilities [1] for
+ * overflowing doubles 'silently' as IEEE fp does. Therefore we
+ * need to detect early whether we would overflow (this is
+ * the behaviour of the native string-to-float conversion routines,
+ * and therefore the behaviour of native applications, too.)
+ *
+ * [1] VAXC$EXTABLISH is the capability but it is basically a signal
+ * handler setup routine, and one cannot return from a fp exception
+ * handler and except much anything useful. */
+#if defined(VMS) && !defined(__IEEE_FP)
# if defined(__DECC_VER) && __DECC_VER <= 50390006
/* __F_FLT_MAX_10_EXP - 5 == 33 */
if (!negative &&
return NV_MAX;
# endif
#endif
+
+ /* In UNICOS and in certain Cray models (such as T90) there is no
+ * IEEE fp, and no way at all from C to catch fp overflows gracefully.
+ * There is something you can do if you are willing to use some
+ * inline assembler: the instruction is called DFI-- but that will
+ * disable *all* floating point interrupts, a little bit too large
+ * a hammer. Therefore we need to catch potential overflows before
+ * it's too late. */
+#if defined(_UNICOS) && defined(NV_MAX_10_EXP)
+ if (!negative &&
+ (log10(value) + exponent) >= NV_MAX_10_EXP)
+ return NV_MAX;
+#endif
+
for (bit = 1; exponent; bit <<= 1) {
if (exponent & bit) {
exponent ^= bit;
result *= power;
}
+ /* Floating point exceptions are supposed to be turned off. */
power *= power;
}
return negative ? value / result : value * result;