source: azure_iot_hub/trunk/musl-1.1.18/src/math/roundl.c@ 388

#include "libm.h"

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

static const long double toint = 1/LDBL_EPSILON;

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

        if (e >= 0x3fff+LDBL_MANT_DIG-1)
                return x;
        if (u.i.se >> 15)
                x = -x;
        if (e < 0x3fff-1) {
                FORCE_EVAL(x + toint);
                return 0*u.f;
        }
        y = x + toint - toint - x;
        if (y > 0.5)
                y = y + x - 1;
        else if (y <= -0.5)
                y = y + x + 1;
        else
                y = y + x;
        if (u.i.se >> 15)
                y = -y;
        return y;
}
#endif