round, roundf, roundl - round to nearest integer, away from zero
float roundf(float x);
long double roundl(long double x);
These functions round x to the nearest integer, but
round halfway cases away from zero (regardless of the
current rounding direction), instead of to the nearest even
integer like rint().
The rounded integer value. If x is integral or
infinite, x itself is returned.
No errors other than EDOM and ERANGE can occur. If x
is NaN, then NaN is returned and errno may be set to
The Austin draft contains text about overflow (which might
set errno to ERANGE, or raise an exception). In
practice, the result cannot overflow on any current machine,
so this error-handling stuff is just nonsense. (More
precisely, overflow can happen only when the maximum value
of the exponent is smaller than the number of mantissa bits.
For the IEEE-754 standard 32-bit and 64-bit floating point
numbers the maximum value of the exponent is 128 (resp.
1024), and the number of mantissa bits is 24 (resp.
ceil(3), floor(3), lround(3),