"double log1p(double "x);
"float log1pf(float "x);
"long double log1pl(long double "x);
log1p(x) returns a value equivalent to log (1 + x). It is computed in a way that is accurate even if the value of x is near zero.
BSD, C99. The float and the long double variants are C99 requirements.
exp(3), log(3), expm1(3)