signbit(3) Library Functions Manual signbit(3) signbit - (libm, -lm) #include int signbit(x); glibc (. feature_test_macros(7)): signbit(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L signbit() , . , x . This is not the same as x < 0.0, because IEEE 754 floating point allows zero to be signed. The comparison -0.0 < 0.0 is false, but signbit(-0.0) will return a nonzero value. NaN . signbit() , x , . . attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |signbit() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. POSIX.1-2001, C99. IEC 559 ( IEEE 754/IEEE 854). copysign(3) () Alexander Golubev , Azamat Hackimov , Hotellook, Nikita , Spiros Georgaras , Vladislav , Yuri Kozlov , Kirill Rekhov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () <>. Linux 6.9.1 2 2024 . signbit(3)