github.com/afumu/libc@v0.0.6/musl/src/math/logbl.c (about)

     1  #include <math.h>
     2  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
     3  long double logbl(long double x)
     4  {
     5  	return logb(x);
     6  }
     7  #else
     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