roundl(3) -- Linux man page
NAMEround, roundf, roundl - round to nearest integer, away from zero
#include <math.h> double round(double x);
float roundf(float x);
long double roundl(long double x);
DESCRIPTIONThese 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().
RETURN VALUEThe rounded integer value. If x is integral or infinite, x itself is returned.
ERRORSNo errors other than EDOM and ERANGE can occur. If x is NaN, then NaN is returned and errno may be set to EDOM.
NOTESPOSIX 1003.1-2001 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. 53).)
SEE ALSOceil(3), floor(3), lround(3), nearbyint(3), rint(3), trunc(3)