/**
Generate NaN.
@return Floating-point representation of NaN.
*/
TRIO_PUBLIC double
trio_nan(void)
{
/* Cache the result */
static double result = 0.0;
if (result == 0.0) {
#if defined(TRIO_COMPILER_SUPPORTS_C99)
result = nan(NULL);
#elif defined(NAN) && defined(__STDC_IEC_559__)
result = (double)NAN;
#elif defined(USE_IEEE_754)
result = trio_make_double(ieee_754_qnan_array);
#else
/*
* There are several ways to generate NaN. The one used here is
* to divide infinity by infinity. I would have preferred to add
* negative infinity to positive infinity, but that yields wrong
* result (infinity) on FreeBSD.
*
* This may fail if the hardware does not support NaN, or if
* the Invalid Operation floating-point exception is unmasked.
*/
# if defined(TRIO_PLATFORM_UNIX)
void (*signal_handler)(int) = signal(SIGFPE, SIG_IGN);
# endif
result = trio_pinf() / trio_pinf();
# if defined(TRIO_PLATFORM_UNIX)
signal(SIGFPE, signal_handler);
# endif
#endif
}
return result;
}
/*************************************************************************
* trio_pinf
*/
TRIO_PUBLIC double
trio_pinf(void)
{
/* Cache the result */
static double result = 0.0;
if (result == 0.0) {
#if defined(INFINITY) && defined(__STDC_IEC_559__)
result = (double)INFINITY;
#elif defined(USE_IEEE_754)
result = trio_make_double(ieee_754_infinity_array);
#else
/*
* If HUGE_VAL is different from DBL_MAX, then HUGE_VAL is used
* as infinity. Otherwise we have to resort to an overflow
* operation to generate infinity.
*/
# if defined(TRIO_PLATFORM_UNIX)
void (*signal_handler)(int) = signal(SIGFPE, SIG_IGN);
# endif
result = HUGE_VAL;
if (HUGE_VAL == DBL_MAX) {
/* Force overflow */
result += HUGE_VAL;
}
# if defined(TRIO_PLATFORM_UNIX)
signal(SIGFPE, signal_handler);
# endif
#endif
}
return result;
}