round(3) Library Functions Manual round(3) round, roundf, roundl - (libm, -lm) #include double round(double x); float roundf(float x); long double roundl(long double x); glibc (. feature_test_macros(7)): round(), roundf(), roundl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L x , ( , fenv(3)), , rint(3). , round(0.5) 1.0, round(-0.5) -1.0. . x , +0, -0, NaN , x. . attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |round(), roundf(), roundl() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. glibc 2.1. C99, POSIX.1-2001. POSIX.1-2001 contains text about overflow (which might set errno to ERANGE, or raise an FE_OVERFLOW exception). In practice, the result cannot overflow on any current machine, so this error-handling stuff was 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 127 (respectively, 1023), and the number of mantissa bits including the implicit bit is 24 (respectively, 53).) This was removed in POSIX.1-2008. , , lround(3). ceil(3), floor(3), lround(3), nearbyint(3), rint(3), trunc(3) () aereiae , Azamat Hackimov , Dmitriy S. Seregin , Katrin Kutepova , Lockal , Yuri Kozlov , , Kirill Rekhov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () <>. Linux 6.9.1 16 2024 . round(3)