1 #include <math.h>
2 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
logbl(long double x)3 long double logbl(long double x)
4 {
5 	return logb(x);
6 }
7 #else
logbl(long double x)8 long double logbl(long double x)
9 {
10 	if (!isfinite(x))
11 		return x * x;
12 	if (x == 0)
13 		return -1/(x*x);
14 	return ilogbl(x);
15 }
16 #endif
17