ref: 1da7f45ae0e42aff174c695d948449bf22bf4b33
dir: /lib/c/atol.c/
#include <ctype.h> #include <stdlib.h> #undef atol long atol(const char *s) { int sign = -1; long n; while (isspace(*s)) ++s; switch (*s) { case '-': sign = 1; case '+': ++s; } /* Compute n as a negative number to avoid overflow on LONG_MIN */ for (n = 0; isdigit(*s); ++s) n = 10*n - (*s - '0'); return sign * n; }