ref: a7140d1787745b7e481425f820507051a132cfb1
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;
}