log1p(3) Library Functions Manual log1p(3) log1p, log1pf, log1pl - 1 (libm, -lm) #include double log1p(double x); float log1pf(float x); long double log1pl(long double x); glibc (. feature_test_macros(7)): log1p(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE log1pf(), log1pl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE log(1 + x) , , x . (1 + x). x NaN, NaN. x , . x -1, , -HUGE_VAL, -HUGE_VALF -HUGE_VALL, . x -1 ( ), , NaN (Not a Number, ). math_error(7), , . : Domain error: x is less than -1. errno EDOM ( . ). (FE_INVALID). Pole error: x is -1. errno ERANGE ( ). (FE_DIVBYZERO). attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |log1p(), log1pf(), log1pl() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. C99, POSIX.1-2001. glibc 2.22 glibc errno EDOM . Before glibc 2.22, the glibc implementation did not set errno to ERANGE when a range error occurred. exp(3), expm1(3), log(3) () Artyom Kunyov , Azamat Hackimov , Dmitry Bolkhovskikh , Katrin Kutepova , Konstantin Shvaykovskiy , Yuri Kozlov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () . Linux man-pages 6.18 8 2026 . log1p(3)