source: azure_iot_hub/trunk/musl-1.1.18/src/math/ceill.c@ 389

#include "libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double ceill(long double x)
{
        return ceil(x);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384

static const long double toint = 1/LDBL_EPSILON;

long double ceill(long double x)
{
        union ldshape u = {x};
        int e = u.i.se & 0x7fff;
        long double y;

        if (e >= 0x3fff+LDBL_MANT_DIG-1 || x == 0)
                return x;
        /* y = int(x) - x, where int(x) is an integer neighbor of x */
        if (u.i.se >> 15)
                y = x - toint + toint - x;
        else
                y = x + toint - toint - x;
        /* special case because of non-nearest rounding modes */
        if (e <= 0x3fff-1) {
                FORCE_EVAL(y);
                return u.i.se >> 15 ? -0.0 : 1;
        }
        if (y < 0)
                return x + y + 1;
        return x + y;
}
#endif