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 || /* glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE log1pf(), log1pl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since 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 ( ). math_error(7) . : : x -1. errno EDOM ( BUGS). (FE_INVALID). : x -1. errno ERANGE ( BUGS). (FE_DIVBYZERO). attributes(7). +------------+------------------------------------+--------------------+ || | | +------------+------------------------------------+--------------------+ |log1p(), | | MT-Safe | |log1pf(), | | | |log1pl() | | | +------------+------------------------------------+--------------------+ C11, POSIX.1-2008. C99 POSIX.1-2001. glibc 2.22 glibc errno EDOM . glibc 2.22 glibc errno ERANGE . exp(3), expm1(3), log(3) 3 . . : . 6.18 8 2026 log1p(3)